This document discusses various forms of corrosion that can affect aluminium and aluminium alloys. It describes general corrosion that can occur in acid and neutral solutions. It also covers localized corrosion such as pitting, crevice, filiform, and biological corrosion. Factors influencing galvanic and intergranular corrosion are presented. The document also discusses mechanically assisted degradation like erosion, fretting corrosion, and corrosion fatigue. It concludes with descriptions of stress corrosion cracking and hydrogen embrittlement.
1) Three-dimensional electrode technology shows potential for wastewater treatment. Optimization of feeder electrodes and development of novel particle electrodes, such as carbon materials and metal oxides, are research focuses.
2) Pollutants are degraded through direct and indirect oxidation near the electrode. However, high operation costs, feeder electrode corrosion, and particle electrode inactivation are challenges.
3) Potential solutions have been proposed, including the use of materials like titanium coated with ruthenium oxide, antimony-doped tin oxide, or boron-doped diamond to address electrode corrosion and inactivation issues.
Chemistry perfect-score-module-form-4-set-3Mudzaffar Shah
1) Electrolysis involves passing an electric current through an electrolyte to cause non-spontaneous redox reactions to occur at the electrodes.
2) Products of electrolysis depend on the nature of the electrolyte and electrodes. Selective discharge of ions occurs based on their position in the electrochemical series.
3) Voltaic cells involve spontaneous redox reactions that generate electricity, with electrons flowing from the negative to the positive terminal.
1. Redox reactions involve the transfer of electrons between oxidizing and reducing agents, resulting in a change in oxidation state.
2. Rusting of iron is a redox reaction where iron is oxidized by oxygen, releasing electrons. Water and oxygen gain electrons to form hydroxide ions.
3. When iron is in contact with more electropositive metals like magnesium or zinc, rusting is inhibited as the more reactive metal undergoes oxidation instead of the iron. Contact with less electropositive metals like copper or tin accelerates rusting as iron is more easily oxidized.
The document is a periodic table of the elements that lists all 118 known elements by their atomic number, element name, symbol, atomic mass, and classification. It provides the essential information about all elements in an organized table format for easy reference.
The document provides information about chemical structures and compounds. It discusses examples of compounds like methane, sodium chloride, and glucose. It also discusses the bonding between elements in compounds, including ionic bonding between sodium and chlorine atoms and covalent bonding between hydrogen and chlorine atoms. Various molecular structures are depicted including water, oxygen, nitrogen, methane, carbon dioxide, and ammonia.
WebElements is a website that provides information about the chemical elements in an interactive periodic table format. It contains details on each element including their name, symbol, atomic number, atomic mass, basic properties and more. The document provides an overview of the periodic table displayed on the site, including information on element names, symbols, atomic weights and organization of the table. It also notes that clicking on an element in the PDF version of the table will link to more details on that element page on the WebElements site when viewed online.
Assignment s block-elements_jh_sir-4173NEETRICKSJEE
The document contains information about s-block elements and their compounds. It begins with an introduction to the topic and syllabus which covers preparation and properties of oxides, peroxides, hydroxides, carbonates, bicarbonates, chlorides and sulphates of sodium, potassium, magnesium and calcium. It then discusses the anomalous properties of lithium and beryllium compared to other elements in their groups. Finally, it provides details on the preparation and properties of specific compounds of alkali metals such as sodium oxide, sodium peroxide, and potassium superoxide.
The document discusses the boron and carbon family (groups 13-14) of the periodic table. It provides information on their electronic configurations, atomic properties, oxidation states, chemical properties including reactivity with air, acids, bases and halogens. It notes the anomalous properties of boron compared to other family members due to the absence of d-orbitals. Examples of compounds in each group are also given such as borax, boric acid, aluminium chloride and oxides.
1) Three-dimensional electrode technology shows potential for wastewater treatment. Optimization of feeder electrodes and development of novel particle electrodes, such as carbon materials and metal oxides, are research focuses.
2) Pollutants are degraded through direct and indirect oxidation near the electrode. However, high operation costs, feeder electrode corrosion, and particle electrode inactivation are challenges.
3) Potential solutions have been proposed, including the use of materials like titanium coated with ruthenium oxide, antimony-doped tin oxide, or boron-doped diamond to address electrode corrosion and inactivation issues.
Chemistry perfect-score-module-form-4-set-3Mudzaffar Shah
1) Electrolysis involves passing an electric current through an electrolyte to cause non-spontaneous redox reactions to occur at the electrodes.
2) Products of electrolysis depend on the nature of the electrolyte and electrodes. Selective discharge of ions occurs based on their position in the electrochemical series.
3) Voltaic cells involve spontaneous redox reactions that generate electricity, with electrons flowing from the negative to the positive terminal.
1. Redox reactions involve the transfer of electrons between oxidizing and reducing agents, resulting in a change in oxidation state.
2. Rusting of iron is a redox reaction where iron is oxidized by oxygen, releasing electrons. Water and oxygen gain electrons to form hydroxide ions.
3. When iron is in contact with more electropositive metals like magnesium or zinc, rusting is inhibited as the more reactive metal undergoes oxidation instead of the iron. Contact with less electropositive metals like copper or tin accelerates rusting as iron is more easily oxidized.
The document is a periodic table of the elements that lists all 118 known elements by their atomic number, element name, symbol, atomic mass, and classification. It provides the essential information about all elements in an organized table format for easy reference.
The document provides information about chemical structures and compounds. It discusses examples of compounds like methane, sodium chloride, and glucose. It also discusses the bonding between elements in compounds, including ionic bonding between sodium and chlorine atoms and covalent bonding between hydrogen and chlorine atoms. Various molecular structures are depicted including water, oxygen, nitrogen, methane, carbon dioxide, and ammonia.
WebElements is a website that provides information about the chemical elements in an interactive periodic table format. It contains details on each element including their name, symbol, atomic number, atomic mass, basic properties and more. The document provides an overview of the periodic table displayed on the site, including information on element names, symbols, atomic weights and organization of the table. It also notes that clicking on an element in the PDF version of the table will link to more details on that element page on the WebElements site when viewed online.
Assignment s block-elements_jh_sir-4173NEETRICKSJEE
The document contains information about s-block elements and their compounds. It begins with an introduction to the topic and syllabus which covers preparation and properties of oxides, peroxides, hydroxides, carbonates, bicarbonates, chlorides and sulphates of sodium, potassium, magnesium and calcium. It then discusses the anomalous properties of lithium and beryllium compared to other elements in their groups. Finally, it provides details on the preparation and properties of specific compounds of alkali metals such as sodium oxide, sodium peroxide, and potassium superoxide.
The document discusses the boron and carbon family (groups 13-14) of the periodic table. It provides information on their electronic configurations, atomic properties, oxidation states, chemical properties including reactivity with air, acids, bases and halogens. It notes the anomalous properties of boron compared to other family members due to the absence of d-orbitals. Examples of compounds in each group are also given such as borax, boric acid, aluminium chloride and oxides.
This is an effort to make ppt of p block elements , a topic in XII, chemistry(cbse) , whom as a tutor i have often felt students are horrified due to its large text size, long descriptipns, several information to be remembered and several reasonings to keep in mind.
Hope this ppt would solve thier problem of a thorough preparation of topic with all important aspects covered in the ppt.
Founder Dr Mona Srivastava
Masterchemclasses
IB Chemistry on Chemical Properties, Oxides and Chlorides of period 3Lawrence kok
The document summarizes periodic trends across period 3 from metals to nonmetals. It discusses how physical and chemical properties change, including bonding type and reactivity. Oxides and chlorides of elements in period 3 are specifically examined, noting how they may react with water through hydrolysis, producing acids or bases depending on the element. Some oxides like aluminum and silicon oxides are noted to not react with water directly but can react with acids or bases.
The document discusses the properties of group 16 (chalcogen) elements (oxygen, sulfur, selenium, tellurium, polonium). Key points include:
- They have the general electronic configuration of ns2np4 and can exhibit oxidation states of -2, +2, +4, and +6.
- Properties vary periodically down the group with atomic size increasing and ionization energy/electronegativity decreasing.
- Oxygen is a gas that forms strong diatomic bonds while sulfur exists as solid rings.
- Important compounds formed include hydrides, halides like sulfur hexafluoride, and oxoacids such as sulfuric acid.
- O
- The elements in Group 15 show increasing covalent radius and decreasing ionization energy down the group, due to additional shells. Nitrogen behaves anomalously due to small size and high electronegativity.
- They form trihydrides (MH3), trioxides (M2O3), and pentoxides (M2O5) with decreasing acidity down the group. They also form trihalides and pentahalides.
- Oxygen is industrially produced from air or water and is essential for respiration and combustion. Ozone is a reactive allotrope produced from oxygen that is used for sterilization and bleaching.
The topic is important for UG students. it covers almost all concepts of metallurgy. The important method of separation of ores, Ellingham diagram and its application.
This document discusses the nomenclature (naming systems) for inorganic compounds, which differ depending on whether the compound is ionic or molecular. For ionic compounds, the cation is named first followed by the anion. Binary ionic compounds consisting of a metal and nonmetal are generally named by removing the ending from the nonmetal and adding -ide. For transition metals that form multiple ions, the modern system uses Roman numerals in parentheses after the metal to indicate charge. Molecular compounds are named by identifying the number of atoms of each element present using prefixes, and adding -ide to the second element. Several elements exist as diatomic molecules like H2, N2, O2, F2, Cl2, Br
The document discusses p-block elements, which include groups 13 through 18 on the periodic table. Some key points:
- Most p-block elements are non-metals that can have variable oxidation states and form acidic oxides. They have high ionization potentials and electron gain enthalpies.
- Properties like metallic character and reactivity generally increase moving down each group as atomic size increases and ionization energy decreases.
- Nitrogen exhibits some anomalous properties compared to other group 15 elements due to its small size, high electronegativity, and lack of d orbitals.
Redox reactions involve the transfer of electrons between chemical species, resulting in both oxidation and reduction processes.
Some key points about redox reactions from the document include:
1) During redox reactions, oxidation states of atoms change as electrons are lost or gained. For example, in the reaction of potassium chlorate, chlorine is reduced from an oxidation state of +5 to -1 while oxygen is oxidized from -2 to 0.
2) The equivalent weight of a substance is calculated based on its stoichiometry and oxidation state changes during redox reactions.
3) Spontaneous redox reactions occur when species with more positive (less negative) standard reduction potentials undergo oxidation, while species
p-BLOCK ELEMENTS,Boron Family (Group 13 Elements )
Compounds of Boron,Orthoboric acid (H3BO3),Borax (sodium tetraborate) Na2B4O7. 10H2O,Diborane,Compounds of Aluminium,Aluminium Oxide or Alumina (Al2O3),
Aluminum Chloride AlCl3,Carbon Family (Group 14 Elements):
Compounds of Carbon,Carbon Monoxide,Carbon di-oxide,
Carbides, Nitrogen Family (Group 15 Elements),
Ammonia (NH3),Phosphorus,Phosphorous Halides,Oxides of Phosphorus,Oxy – Acids of Phosphorus,Oxygen Family (Group 16 Elements) , Allotropes of Sulphur,Halogen Family ( Group 17 Elements,Inter halogen compounds,
Hydrogen Halides,Pseudohalide ions and pseudohalogens,Some important stable compound of Xenon
This document provides information about the boron family of elements. It discusses the occurrence, properties, and reactions of boron, aluminum, gallium, indium, and thallium. It focuses on boron compounds such as boranes, diborane, and borohydrides. It discusses the inert pair effect which causes the stability of lower oxidation states for heavier group 13 elements. The document also provides background on fullerenes including their discovery and C60 buckminsterfullerene.
The document discusses trends in the properties of group 15 elements of the periodic table, which include nitrogen, phosphorus, arsenic, antimony, and bismuth. It notes that ionization energy decreases and atomic/ionic radii increase down the group as atomic size increases. Nitrogen and phosphorus are nonmetals, arsenic and antimony are metalloids, and bismuth is a metal. The electronic configuration is ns2np3 and oxidation states vary between -3 to +5, with the most common being -3, +3, and +5.
The document discusses the group 16 (oxygen family) elements of the periodic table. It covers their general electronic configuration of ns2np4, trends in periodic properties like atomic radius and ionization energy decreasing down the group. It describes the common oxidation states of -2, +2, +4 and +6. It also discusses the formation of hydrides, halides, oxides and reactions with air, acids, alkalis and metals for these chalcogen elements.
This document provides information on p-block elements from the chemistry class. It discusses the electronic configuration of p-block elements and their general characteristics, including variation in oxidation states, metallic and non-metallic properties, and differences in behavior between the first element of each group and other members. Specific groups like group 13 (boron family) and group 14 (carbon family) are examined in more detail regarding electronic structures, properties, and structures of compounds.
Nitrogen and oxygen are important nonmetals that are essential for living things. Nitrogen makes up 78% of the atmosphere as N2 gas but must be "fixed" by bacteria to be used by most organisms. It is obtained commercially by fractional distillation of air or by removing oxygen from air over hot coke. Nitrogen is used to make ammonia and nitric acid, which are used in fertilizers and explosives. Oxygen makes up 23% of the atmosphere and is vital for animal respiration. It is obtained industrially by fractionally distilling liquefied air. Oxygen is used in steel production, pigments, rocket fuel, medicine, and other industrial processes. Sulfur is a yellow solid
The document provides information on elements and compounds. It defines an element as a substance that cannot be broken down further by chemical means, while a compound is made up of two or more elements chemically bonded together. Elements are the fundamental building blocks and are made of only one type of atom. Compounds have molecules made of two or more atom types. The document explains how to write chemical formulas and balanced equations to represent elements, compounds and chemical reactions.
The document discusses the nomenclature of inorganic compounds according to IUPAC rules. It covers naming conventions for binary ionic compounds such as metal oxides, salts, metal hydrides, non-metal halides, and binary acids. It also discusses determining oxidation states and writing chemical formulas. Key points include naming metal oxides as "stock name of metal cation" + "oxide", salts as "stock name of metal cation" + "root name of non-metal anion" + "-ide", and distinguishing between ionic and molecular compounds in nomenclature.
Chemical properties of p block elements .Momina Faheem
The document discusses the chemical properties of various p-block elements. It describes how elements within the groups react with substances like oxygen, hydrogen, halogens and metals. For example, it notes that aluminum burns in air if powdered, reacts with chlorine, and does not react with alkalis like sodium hydroxide at moderate temperatures. It also summarizes the reactions of group 13 (boron forms trihalides), group 14 (carbon remains unreactive with air), group 15 (nitrogen reacts with hydrogen to form ammonia), group 16 (oxygen readily forms compounds with most elements), group 17 (halogens react with hydrogen to form hydrogen halides) and group 18 elements (noble gases
This lecture describes the process of anodic oxidation of aluminium, which is one of the most unique and commonly used surface treatment techniques for aluminium; it illustrates the weathering behaviour of anodized surfaces. Some familiarity with the subject matter covered in TALAT This lectures 5101- 5104 is assumed.
surface characteristics and electrochemical impedance investigation of spark-...mohammad fazel
This document summarizes a study that investigated the surface characteristics of oxide films formed on Ti-6Al-4V alloy by spark anodization in H2SO4/H3PO4 electrolyte at different voltages. The results showed that increasing the anodization voltage increased the pore diameter and porosity of the oxide layer. Higher voltages also produced thicker oxide layers and rougher surfaces. Analysis found the layers incorporated elements from the electrolyte and consisted of crystalline anatase. Electrochemical testing indicated the impedance behavior was affected by the space charge region, inner compact layer and outer porous layer, and that corrosion resistance decreased with higher voltages.
TALAT Lecture 5301: The Surface Treatment and Coil Coating of AluminiumCORE-Materials
This lecture describes the continuous coil coating processes for aluminium in sufficient detail in order to understand the industrial coating technology and its application potential. General background in materials engineering and familiarity with the subject matter covered in TALAT This lectures 5100 and 5200 is assumed.
1. Corrosion is an electrochemical process involving oxidation and reduction reactions. It requires an anode, cathode, electrolyte, and an electrically conducting path.
2. At the anode, iron oxidizes to ferrous ions which then react with hydroxyl ions from the cathode to form iron hydroxide and iron oxide. The products occupy more volume than the original steel causing stresses in the concrete.
3. Chlorides from deicing salts or seawater can destroy the protective oxide layer and accelerate corrosion. Carbonation reduces concrete's alkalinity allowing the protective layer to break down.
This is an effort to make ppt of p block elements , a topic in XII, chemistry(cbse) , whom as a tutor i have often felt students are horrified due to its large text size, long descriptipns, several information to be remembered and several reasonings to keep in mind.
Hope this ppt would solve thier problem of a thorough preparation of topic with all important aspects covered in the ppt.
Founder Dr Mona Srivastava
Masterchemclasses
IB Chemistry on Chemical Properties, Oxides and Chlorides of period 3Lawrence kok
The document summarizes periodic trends across period 3 from metals to nonmetals. It discusses how physical and chemical properties change, including bonding type and reactivity. Oxides and chlorides of elements in period 3 are specifically examined, noting how they may react with water through hydrolysis, producing acids or bases depending on the element. Some oxides like aluminum and silicon oxides are noted to not react with water directly but can react with acids or bases.
The document discusses the properties of group 16 (chalcogen) elements (oxygen, sulfur, selenium, tellurium, polonium). Key points include:
- They have the general electronic configuration of ns2np4 and can exhibit oxidation states of -2, +2, +4, and +6.
- Properties vary periodically down the group with atomic size increasing and ionization energy/electronegativity decreasing.
- Oxygen is a gas that forms strong diatomic bonds while sulfur exists as solid rings.
- Important compounds formed include hydrides, halides like sulfur hexafluoride, and oxoacids such as sulfuric acid.
- O
- The elements in Group 15 show increasing covalent radius and decreasing ionization energy down the group, due to additional shells. Nitrogen behaves anomalously due to small size and high electronegativity.
- They form trihydrides (MH3), trioxides (M2O3), and pentoxides (M2O5) with decreasing acidity down the group. They also form trihalides and pentahalides.
- Oxygen is industrially produced from air or water and is essential for respiration and combustion. Ozone is a reactive allotrope produced from oxygen that is used for sterilization and bleaching.
The topic is important for UG students. it covers almost all concepts of metallurgy. The important method of separation of ores, Ellingham diagram and its application.
This document discusses the nomenclature (naming systems) for inorganic compounds, which differ depending on whether the compound is ionic or molecular. For ionic compounds, the cation is named first followed by the anion. Binary ionic compounds consisting of a metal and nonmetal are generally named by removing the ending from the nonmetal and adding -ide. For transition metals that form multiple ions, the modern system uses Roman numerals in parentheses after the metal to indicate charge. Molecular compounds are named by identifying the number of atoms of each element present using prefixes, and adding -ide to the second element. Several elements exist as diatomic molecules like H2, N2, O2, F2, Cl2, Br
The document discusses p-block elements, which include groups 13 through 18 on the periodic table. Some key points:
- Most p-block elements are non-metals that can have variable oxidation states and form acidic oxides. They have high ionization potentials and electron gain enthalpies.
- Properties like metallic character and reactivity generally increase moving down each group as atomic size increases and ionization energy decreases.
- Nitrogen exhibits some anomalous properties compared to other group 15 elements due to its small size, high electronegativity, and lack of d orbitals.
Redox reactions involve the transfer of electrons between chemical species, resulting in both oxidation and reduction processes.
Some key points about redox reactions from the document include:
1) During redox reactions, oxidation states of atoms change as electrons are lost or gained. For example, in the reaction of potassium chlorate, chlorine is reduced from an oxidation state of +5 to -1 while oxygen is oxidized from -2 to 0.
2) The equivalent weight of a substance is calculated based on its stoichiometry and oxidation state changes during redox reactions.
3) Spontaneous redox reactions occur when species with more positive (less negative) standard reduction potentials undergo oxidation, while species
p-BLOCK ELEMENTS,Boron Family (Group 13 Elements )
Compounds of Boron,Orthoboric acid (H3BO3),Borax (sodium tetraborate) Na2B4O7. 10H2O,Diborane,Compounds of Aluminium,Aluminium Oxide or Alumina (Al2O3),
Aluminum Chloride AlCl3,Carbon Family (Group 14 Elements):
Compounds of Carbon,Carbon Monoxide,Carbon di-oxide,
Carbides, Nitrogen Family (Group 15 Elements),
Ammonia (NH3),Phosphorus,Phosphorous Halides,Oxides of Phosphorus,Oxy – Acids of Phosphorus,Oxygen Family (Group 16 Elements) , Allotropes of Sulphur,Halogen Family ( Group 17 Elements,Inter halogen compounds,
Hydrogen Halides,Pseudohalide ions and pseudohalogens,Some important stable compound of Xenon
This document provides information about the boron family of elements. It discusses the occurrence, properties, and reactions of boron, aluminum, gallium, indium, and thallium. It focuses on boron compounds such as boranes, diborane, and borohydrides. It discusses the inert pair effect which causes the stability of lower oxidation states for heavier group 13 elements. The document also provides background on fullerenes including their discovery and C60 buckminsterfullerene.
The document discusses trends in the properties of group 15 elements of the periodic table, which include nitrogen, phosphorus, arsenic, antimony, and bismuth. It notes that ionization energy decreases and atomic/ionic radii increase down the group as atomic size increases. Nitrogen and phosphorus are nonmetals, arsenic and antimony are metalloids, and bismuth is a metal. The electronic configuration is ns2np3 and oxidation states vary between -3 to +5, with the most common being -3, +3, and +5.
The document discusses the group 16 (oxygen family) elements of the periodic table. It covers their general electronic configuration of ns2np4, trends in periodic properties like atomic radius and ionization energy decreasing down the group. It describes the common oxidation states of -2, +2, +4 and +6. It also discusses the formation of hydrides, halides, oxides and reactions with air, acids, alkalis and metals for these chalcogen elements.
This document provides information on p-block elements from the chemistry class. It discusses the electronic configuration of p-block elements and their general characteristics, including variation in oxidation states, metallic and non-metallic properties, and differences in behavior between the first element of each group and other members. Specific groups like group 13 (boron family) and group 14 (carbon family) are examined in more detail regarding electronic structures, properties, and structures of compounds.
Nitrogen and oxygen are important nonmetals that are essential for living things. Nitrogen makes up 78% of the atmosphere as N2 gas but must be "fixed" by bacteria to be used by most organisms. It is obtained commercially by fractional distillation of air or by removing oxygen from air over hot coke. Nitrogen is used to make ammonia and nitric acid, which are used in fertilizers and explosives. Oxygen makes up 23% of the atmosphere and is vital for animal respiration. It is obtained industrially by fractionally distilling liquefied air. Oxygen is used in steel production, pigments, rocket fuel, medicine, and other industrial processes. Sulfur is a yellow solid
The document provides information on elements and compounds. It defines an element as a substance that cannot be broken down further by chemical means, while a compound is made up of two or more elements chemically bonded together. Elements are the fundamental building blocks and are made of only one type of atom. Compounds have molecules made of two or more atom types. The document explains how to write chemical formulas and balanced equations to represent elements, compounds and chemical reactions.
The document discusses the nomenclature of inorganic compounds according to IUPAC rules. It covers naming conventions for binary ionic compounds such as metal oxides, salts, metal hydrides, non-metal halides, and binary acids. It also discusses determining oxidation states and writing chemical formulas. Key points include naming metal oxides as "stock name of metal cation" + "oxide", salts as "stock name of metal cation" + "root name of non-metal anion" + "-ide", and distinguishing between ionic and molecular compounds in nomenclature.
Chemical properties of p block elements .Momina Faheem
The document discusses the chemical properties of various p-block elements. It describes how elements within the groups react with substances like oxygen, hydrogen, halogens and metals. For example, it notes that aluminum burns in air if powdered, reacts with chlorine, and does not react with alkalis like sodium hydroxide at moderate temperatures. It also summarizes the reactions of group 13 (boron forms trihalides), group 14 (carbon remains unreactive with air), group 15 (nitrogen reacts with hydrogen to form ammonia), group 16 (oxygen readily forms compounds with most elements), group 17 (halogens react with hydrogen to form hydrogen halides) and group 18 elements (noble gases
This lecture describes the process of anodic oxidation of aluminium, which is one of the most unique and commonly used surface treatment techniques for aluminium; it illustrates the weathering behaviour of anodized surfaces. Some familiarity with the subject matter covered in TALAT This lectures 5101- 5104 is assumed.
surface characteristics and electrochemical impedance investigation of spark-...mohammad fazel
This document summarizes a study that investigated the surface characteristics of oxide films formed on Ti-6Al-4V alloy by spark anodization in H2SO4/H3PO4 electrolyte at different voltages. The results showed that increasing the anodization voltage increased the pore diameter and porosity of the oxide layer. Higher voltages also produced thicker oxide layers and rougher surfaces. Analysis found the layers incorporated elements from the electrolyte and consisted of crystalline anatase. Electrochemical testing indicated the impedance behavior was affected by the space charge region, inner compact layer and outer porous layer, and that corrosion resistance decreased with higher voltages.
TALAT Lecture 5301: The Surface Treatment and Coil Coating of AluminiumCORE-Materials
This lecture describes the continuous coil coating processes for aluminium in sufficient detail in order to understand the industrial coating technology and its application potential. General background in materials engineering and familiarity with the subject matter covered in TALAT This lectures 5100 and 5200 is assumed.
1. Corrosion is an electrochemical process involving oxidation and reduction reactions. It requires an anode, cathode, electrolyte, and an electrically conducting path.
2. At the anode, iron oxidizes to ferrous ions which then react with hydroxyl ions from the cathode to form iron hydroxide and iron oxide. The products occupy more volume than the original steel causing stresses in the concrete.
3. Chlorides from deicing salts or seawater can destroy the protective oxide layer and accelerate corrosion. Carbonation reduces concrete's alkalinity allowing the protective layer to break down.
A presentation covering the various methods of prevention of corrosion. Material selection, design of structures, alteration of materials, alteration of environment, cathodic & anodic protection, and coatings are the different methods used. These are briefly described.
This document discusses cathodic and anodic protection techniques to prevent corrosion of metal structures. It describes two methods of cathodic protection: 1) sacrificial anodic protection which uses more reactive "sacrificial anodes" connected to the structure, and 2) impressed current cathodic protection which uses an external current source and inert anode. Applications include protecting underground pipelines, cables, ship hulls, tanks, and more. The document also covers anodic protection which makes the metal structure the anode and controls its potential to reduce corrosion, using a technique called potentiostat.
This document provides an overview of surface treatment methods for aerospace components, including anodization, ultrasonic solvent cleaning, pickling-passivation, chemical cleaning, and vapour degreasing. It acknowledges those who helped with the project work. Tables of contents and figures/tables are included. The abstract indicates that tests were conducted to determine which surface treatment methods are suitable for different metals used in aerospace and whether thickness, hardness, porosity, and corrosion resistance met specifications.
Corrosion is the destruction of metals through reaction with the environment. It can occur in dry or wet environments and causes economic and safety issues. There are two main types of corrosion: general/uniform corrosion, which occurs at the same rate over the entire surface, and localized corrosion, which affects only certain areas. Methods of preventing corrosion include proper material selection, protective coatings like paint and plating, cathodic protection, and design considerations. Non-ferrous metals are metals that do not contain much iron and include aluminum, copper, zinc, and others which are used due to properties like corrosion resistance.
The document discusses corrosion and its theories. It defines corrosion as the gradual deterioration of a metal through a chemical or electrochemical reaction with its environment. There are three main theories of corrosion discussed: acid theory, dry/chemical corrosion, and electrochemical/wet corrosion. Electrochemical corrosion involves the formation of an anode and cathode on a metal surface when it is exposed to an electrolyte. Metal ions are released at the anode through oxidation and electrons flow to the cathode. The document also discusses types of corrosion like galvanic corrosion and factors that influence corrosion.
A presentation giving the basic principles of corrosion. Electrochemical nature of corrosion, anodic and cathodic reactions, electrode potentials, mixed potential theory and kinetics of corrosion, thermodynamics of corrosion and Pourbaix diagrams, and passivization behavior of metals are outlined.
A SHORT REVIEW ON ALUMINIUM ANODIZING: AN ECO-FRIENDLY METAL FINISHING PROCESSJournal For Research
Protection of aluminium alloys is most commonly done by forming anodic films. Anodic films can also be formed on metals like titanium, zinc, magnesium, niobium, and tantalum. Aluminium alloy parts are anodized to greatly increase the thickness of the natural oxide layer for corrosion resistance. A thin aluminium oxide film, that seals the aluminium from further oxidation when it is exposed to air. The anodizing process increases the thickness of the oxidized surface. Anodizing is accomplished by immersing the aluminium into an acid electrolyte bath and passing an electric current through the medium. In an anodizing cell, the aluminium work piece is made the anode by connecting it to the positive terminal of a dc power supply and the cathode is connected to the negative terminal of the dc source. Sealing is needed to seal the pores in oxide layer to prevent further corrosion. Oxide layer on the anodized aluminium has a highly ordered, porous structure that allows for secondary processes such as dyeing, printing and sealing. Nanowires and nanotubes can be made by using the pores in the oxide layer as templates.
Corrosion is the deterioration of materials due to chemical or electrochemical reaction with the environment. It is an inevitable process that leads to significant economic losses. Corrosion engineering studies corrosion mechanisms and works to prevent or control corrosion economically and safely. Common types of corrosion include galvanic, erosion, crevice, pitting, and microbiologically influenced corrosion. Factors that influence corrosion include the metal properties, environmental conditions like temperature, pH, and presence of ions. Protection methods include material selection, cathodic protection, modifying the environment, metallic coatings, inorganic coatings, and organic coatings.
This document describes an electrochemical study of the anodic oxidation of titanium and a TA6V alloy in chromic acid electrolytes. Voltammetry and chronoamperometry experiments were conducted to investigate the formation of oxide films. In a chromic acid electrolyte without fluoride, a thin compact oxide film forms, while in a fluoride-containing electrolyte, a duplex film of a compact layer topped by a porous columnar layer grows. The voltammetry results show a breakdown of the compact film around 3 V/SCE and that alloying elements influence porous film formation. Chronoamperometry reveals the complex growth process involves residual current contributing to thickening of both layers, with overall electrochemical efficiency decreasing over
This document provides information about acids and bases, including their properties and reactions. It defines acids as substances that produce hydrogen ions in aqueous solution, and bases as metal oxides or hydroxides. Strong acids are fully ionized in water, while weak acids are only partially ionized. The strength of an acid does not relate to its concentration. Common uses of acids include battery electrolytes, rust removal, and food preservation.
1. Corrosion is the deterioration and loss of solid metallic material by chemical or electrochemical attack by its environment.
2. There are two main types of corrosion: dry/chemical corrosion which occurs through direct chemical action, and wet/electrochemical corrosion which occurs when a conducting liquid is in contact with the metal.
3. Wet corrosion occurs via separate anodic and cathodic reactions - the anodic reaction involves metal dissolution or compound formation, while the cathodic reaction involves hydrogen evolution in acidic environments or oxygen absorption in basic environments.
Hand book-of-electroplating-anodizing-surface-finishingFany van Lopez
This document provides an overview of electroplating, anodizing, and surface finishing technologies. It discusses various metal deposition processes like electroplating of nickel, chromium, copper, silver, gold, cadmium, zinc, tin, and their alloys. It also covers plating on non-metallic surfaces like plastics. Various metal pretreatment processes like cleaning, pickling and etching are described. Operating conditions, equipment used, and solutions for different plating processes are provided.
This document summarizes key points from Lecture 17 on corrosion and oxidation of metals. It discusses corrosion in terms of thermodynamics and kinetics, surface and interface reactions during metal oxidation, and models for oxidation of silicon. It also covers mechanisms of corrosion like galvanic corrosion, the formation of protective oxide films, and how to measure corrosion rates. Standard electrode potentials are presented to compare the tendency of metals to corrode.
The document discusses corrosion, which is the gradual destruction of metals through chemical or electrochemical reaction with the environment. Rusting of iron is a common example. There are two main types of corrosion - direct chemical corrosion which occurs through reaction with gases, and electrochemical corrosion which occurs when a metal is in contact with a conducting liquid. Electrochemical corrosion results from the formation of galvanic cells and the flow of current between anodic and cathodic areas. Methods of controlling corrosion include selecting corrosion-resistant materials, using protective coatings like paints and anodizing, adding corrosion inhibitors, and cathodic protection techniques.
Anodizing is an electrochemical process that converts the metal surface of aluminum to aluminum oxide. It produces a coating that is very durable, corrosion resistant, and maintains the metallic appearance of the aluminum. The anodizing process involves racking parts for processing, cleaning, etching, anodizing in an acid bath using electricity, coloring or sealing the pores, and testing to quality check the coating. Anodized aluminum has advantages like durability, low maintenance, and an environmentally friendly process.
Ferritin oxidizes Fe2+ to Fe3+ before mineralizing the iron in the fer.docxedmundp8cgllams
Ferritin oxidizes Fe2+ to Fe3+ before mineralizing the iron in the ferritin core.?What is the oxidant for this process, and what is the byproduct produced when the oxidant is reduced?
Solution
Ferritin are a family of natural, highly conserved supramolecular nanostructures designed for sequencing the thousands of iron atoms in a mineralised form.
The main important property of ferritin is the protection of DNA from oxidative damage. In presence of atmospheric oxygen at neutral pH, ferrous ion is readily oxidised to ferric form.
In addition to this hydrogen peroxide (H 2 O 2 ) which is a byproduct of oxygen metabaolism is used as an oxidant and catalyse the generation of highly toxic hydroxyl radicals which damages the proteins, membranes and DNA. So inorder to maintain adequate supply of iron, a molecular mechanism was developed which was utilised by ferritin.\\
Toxification reaction : H 2 O 2 + O 2 - -----> OH - + OH * + O 2
(Fe)
Ferritin consists of 2 subunits H(heavy) and L(light). The H subunit have a dinuclear iron center which consists of A and B binding sites where the fast conversion of Fe +2 to Fe +3 by dioxygen or hydrogen peroxide occurs. The L subunit is used for nucleation of iron core and stores it.
Ferrioxidation reaction : 2Fe +2 + O 2 + 4H 2 O -------> 2FeOOH Core + H 2 O 2 + 4H +
1,2- peroxodi-Fe III intermediate
Minerlization reaction : 4Fe +2 + O 2 + 6H 2 O -------> 4FeOOH Core + 8H +
Detoxification reaction : 4Fe +2 + H 2 O 2 + 2H 2 O -----> 2FeOOH Core + 4H +
Net reaction : Â Â 2Fe +2 + O 2 + 4H 2 O + P --------> (P-(Fe 2 O 2 ) FS +2 ----> (P-(Fe 2 O(OH) 2 ) FS +2 ---->
P + 2FeOOH Core + H 2 O 2 + 4H +
.
This document discusses acids and bases from the perspective of oxides, discussing how basic oxides like CaO and BaO react with water to form basic solutions while acidic oxides like SO3, CO2, and N2O5 form acidic aqueous solutions. It also examines amphoteric oxides that can dissolve in acids or bases, as well as how metal complexes can hydrolyze to form acidic solutions with varying strengths depending on the metal ion.
The document discusses electrolysis of aqueous solutions. It explains that aqueous solutions contain anions, cations, and ions from the partial dissociation of water (H+ and OH-). Electrolysis of copper(II) sulfate solution results in copper metal depositing at the cathode and oxygen gas releasing at the anode. Several factors affect the products of electrolysis, including position of ions in the electrochemical series and concentration of electrolytes. The document concludes with an example of the half reactions during electrolysis of copper(II) sulfate solution.
Sulfur has an oxidation number of +4 in SO2 and Na2SO4. Carbon has an oxidation number of +4 in CO32-. Oxygen has an oxidation number of -2 in all cases. Sodium has an oxidation number of +1 in Na2SO4. Nitrogen has an oxidation number of -3 and hydrogen has an oxidation number of +1 in (NH4)2S.
Wet or Electrochemical corrosion, Mechanism of electrochemical corrosion, Evolution of hydrogen and absorption of oxygen type cathodic reaction, Distinction between dry and wet corrosion.
6.3 (a) electrolysis of an aqueous solutionAzieda Dot
The document discusses the electrolysis of aqueous solutions. It explains that during electrolysis, only one ion is selectively discharged at each electrode based on its position in the electrochemical series, the nature of the electrode, and the concentration of ions. The ion discharged at the anode depends on which is easier to oxidize, while the ion discharged at the cathode depends on which is easier to reduce. Different products are formed depending on these factors and the specific electrolyte used.
Electrolysis is the process of using electric current to cause non-spontaneous chemical changes. During electrolysis, ions are discharged at the electrodes. The key factors that determine which ions are discharged include the position of ions in the electrochemical series, concentration of ions, and type of electrode. Electrolysis has various industrial applications including electroplating, metal purification, and metal extraction.
Electrolysis is the process of using electric current to cause non-spontaneous chemical changes. During electrolysis, ions are discharged at the electrodes. The key factors that determine which ions are discharged include the position of ions in the electrochemical series, concentration of ions, and type of electrode. Electrolysis has important industrial applications such as electroplating, metal purification, and metal extraction.
The three main factors that affect the electrolysis of an aqueous solution are:
1) The position of ions in the electrochemical series, which determines which ions will be reduced or oxidized at the electrodes.
2) The concentration of ions or electrolytes in the solution. Higher concentrations result in greater rates of reaction.
3) The type of electrodes used, as certain electrodes may dissolve and alter the composition of the solution during electrolysis.
This document discusses the properties of hydrogen including its resemblance to alkali metals and halogens in terms of electronic configuration and ability to form ions. It describes hydrogen's isotopes, electrolysis of water producing hydrogen and oxygen, and laboratory preparation of hydrogen peroxide from barium peroxide and sodium peroxide which produces hydrogen gas. The document also explains hydrogen peroxide serving as both an oxidizing and reducing agent in chemical reactions and mentions its colorless liquid state, boiling point higher than water, and melting point just below freezing.
Marking scheme-chemistry-perfect-score-module-form-4-set-3Mudzaffar Shah
The document provides information on three electrolysis experiments involving different electrolytes and products observed at the anode and cathode. Experiment 1 uses sodium chloride solution, with chlorine gas produced at the anode and hydrogen gas at the cathode. Experiment 2 uses hydrochloric acid, producing oxygen gas at the anode and hydrogen gas at the cathode. Experiment 3 uses copper sulfate solution, with no ions being discharged and copper metal being deposited at the cathode through the oxidation of copper electrodes.
Okay, here are the steps to balance this reaction:
Step 1) Identify oxidizing and reducing agents:
MnO4- is reduced, so it is the oxidizing agent.
MnO4- + 5e- → Mn2+
SO2 is oxidized, so it is the reducing agent.
SO2 → SO42- + 4e-
Step 2) Balance other elements: No need here.
Step 3) Balance O by adding H2O:
MnO4- + 5e- → Mn2+ + 4H2O
SO2 → SO42- + 4e-
Step 4) Balance H by adding H+:
M
1) The document discusses complexometric titration using EDTA to determine water hardness (Ca2+ and Mg2+ amount) by forming stable metal-EDTA complexes.
2) EDTA is described as an effective chelating agent that forms stable 1:1 complexes with many metal ions through multiple coordination bonds.
3) The titration curve is plotted using calculations that account for changes in metal ion concentration as EDTA is added to react and form complexes. Metal ion indicators are also described that signal the endpoint of the titration through a color change.
This document defines redox reactions as processes where electrons are either gained (reduction) or lost (oxidation). It provides examples of calculating oxidation states and naming ionic compounds. It then discusses a redox reaction between iron(II) chloride and chlorine, writing balanced equations and identifying oxidizing/reducing agents. Finally, it covers a redox reaction between iodide and dichromate ions, including half and overall equations.
Conferencia de Aldo Steinfeld "Liquid Fuels from Water, CO2, and Solar Energy"IMDEA Energia
The document discusses using sunlight, water, carbon dioxide, and solar energy to produce liquid fuels like diesel, jet fuel, and methanol. It describes a two-step thermochemical process where water and carbon dioxide are split into hydrogen, carbon monoxide, and oxygen gases using a metal oxide. These gases can then be converted to liquid fuels. Experimental systems at the 10 kW and 100 kW scale are presented that use concentrated solar energy to drive the endothermic reactions. Testing showed the systems can split zinc oxide to produce oxygen and zinc for further fuel synthesis.
The document summarizes research on liquid fuels production from water, carbon dioxide, and solar energy. Key points:
1) A solar thermochemical process splits water and CO2 into syngas (H2 and CO) using metal oxide redox reactions, which can then be converted to liquid fuels like diesel and jet fuel.
2) Experimental systems at IMDEA Energy have achieved up to 0.8% solar-to-fuel efficiency for CO2 splitting and 0.7% for H2O splitting.
3) Tests simultaneously splitting CO2 and H2O achieved syngas with an H2/CO ratio of 2, suitable for liquid fuels production.
The document summarizes research on liquid fuels production from water, carbon dioxide, and solar energy. Key points:
1) A solar thermochemical process splits water and CO2 into syngas (H2 and CO) using metal oxide redox reactions, which can then be converted to liquid fuels like diesel and jet fuel.
2) Experimental systems at IMDEA Energy have achieved up to 0.8% solar-to-fuel efficiency for CO2 splitting and 0.7% for H2O splitting.
3) Tests simultaneously splitting CO2 and H2O produced syngas with a H2/CO ratio of 2, suitable for liquid fuels synthesis.
The effect of acid deposition is basically the ef.pdfkrram1989
The effect of acid deposition is basically the effect any acid has on metal. It tends to
corrode it. Corrosion is the electrochemical degradation of a material. That means that as the
metal breaks down, it loses electrons to become a different form. Solid iron (Fe) loses electrons
to become a soluble form, Fe(s) --> Fe2+(in solution) + 2e- These electrons are taken up by
oxygen (O2), which reacts with hydrogen ions (H+) to form water. (1/2) O2 + 2H+ + 2e- -->
H2O The overall reaction is , Fe(s) + (1/2) O2 + 2H+ --> Fe2+ + H2O Normally, the H+ can
come from the acid that forms naturally as CO2 dissolves in water. However, acid rain provides
a lot more H+ & makes it much easier for the reaction to run because there is plenty of
everything needed. Once the iron is in solution it can react further to form iron oxide, which is
also known as rusting.
Solution
The effect of acid deposition is basically the effect any acid has on metal. It tends to
corrode it. Corrosion is the electrochemical degradation of a material. That means that as the
metal breaks down, it loses electrons to become a different form. Solid iron (Fe) loses electrons
to become a soluble form, Fe(s) --> Fe2+(in solution) + 2e- These electrons are taken up by
oxygen (O2), which reacts with hydrogen ions (H+) to form water. (1/2) O2 + 2H+ + 2e- -->
H2O The overall reaction is , Fe(s) + (1/2) O2 + 2H+ --> Fe2+ + H2O Normally, the H+ can
come from the acid that forms naturally as CO2 dissolves in water. However, acid rain provides
a lot more H+ & makes it much easier for the reaction to run because there is plenty of
everything needed. Once the iron is in solution it can react further to form iron oxide, which is
also known as rusting..
The document discusses electrolysis and the principles behind it. It explains that electrolysis involves passing electricity through an electrolyte, which causes chemical decomposition. Ions migrate to the electrodes and are discharged. Metals are formed at the cathode by reduction, while non-metals or oxygen form at the anode by oxidation. It provides examples of electrolysis such as molten salts like NaCl and aqueous solutions like copper sulfate. Factors affecting ion discharge are also discussed.
The document discusses oxidation-reduction (redox) reactions. It defines redox reactions as chemical reactions involving simultaneous oxidation and reduction. Oxidation involves losing electrons, hydrogen, or gaining oxygen, while reduction involves gaining electrons, hydrogen, or losing oxygen. Redox reactions have oxidation and reduction half-reactions, and involve oxidizing and reducing agents. Oxidizing agents cause oxidation, while reducing agents cause reduction. The document provides examples of redox reactions involving changes in oxygen, hydrogen, electrons, and oxidation states to illustrate oxidation and reduction. It also discusses using half-reactions and oxidation numbers to identify the oxidizing and reducing agents in redox reactions.
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TALAT Lecture 5103: Corrosion Control of Aluminium - Forms of Corrosion and Prevention
1. TALAT Lectures 5103
Corrosion Control of Aluminium
-Forms of Corrosion and Prevention-
20 pages, 11 figures
Basic Level
prepared by J. Vereecken, Vrije Universiteit Brussels
Objectives:
− To understand the corrosion principles and to select protection methods
− To be able to use aluminium optimally even in aggressive environments
Prerequisites:
− Metallurgy of aluminium
− Electrochemistry
Date of Issue: 1994
EAA - European Aluminium Association
2. 5103 Corrosion Control of Aluminium - Forms of
Corrosion and Prevention -
Table of Contents
5103 Corrosion Control of Aluminium - Forms of Corrosion and Prevention -......2
5103.01 General Corrosion .................................................................................... 3
Corrosion in Acid Solutions ....................................................................................3
Corrosion in Neutral Solutions ................................................................................4
Passivation ...............................................................................................................5
Corrosion of Aluminium and Aluminium Alloys....................................................6
5103.02 Localized Corrosion.................................................................................. 7
Environmentally Influenced Corrosion....................................................................7
Pitting Corrosion ................................................................................................ 7
Crevice Corrosion............................................................................................... 9
Filiform Corrosion............................................................................................ 10
Biological Corrosion ........................................................................................ 11
Metallurgically Influenced Corrosion ....................................................................12
Galvanic Corrosion .......................................................................................... 12
Intergranular Corrosion ................................................................................... 13
Mechanically Assisted Degradation.......................................................................13
Erosion.............................................................................................................. 13
Fretting Corrosion............................................................................................ 14
Corrosion Fatigue............................................................................................. 14
Environmentally Induced Cracking .......................................................................15
Stress Corrosion Cracking (SCC)..................................................................... 15
Hydrogen Embrittlement................................................................................... 16
5103.03 Corrosion Prevention.............................................................................. 16
Alloy and Temper Selection ..................................................................................17
Design of Equipment .............................................................................................17
Organic Coating .....................................................................................................18
Inhibitors ................................................................................................................18
Anorganic Surface Treatments (see Lectures 5201, 5202 and 5205) ....................19
Cathodic Protection................................................................................................19
5103.04 References/Literature ............................................................................. 19
5103.05 List of Figures............................................................................................ 20
TALAT 5103 2
3. 5103.01 General Corrosion
• Corrosion in acid solutions
• Corrosion in neutral solutions
• Passivation
• Corrosion of aluminium and aluminium alloys
Corrosion in Acid Solutions
Corrosion of a metal (such as Me) occurs in acid solutions due to the simultaneous metal
oxidation and proton reduction :
Me ! Me2+ + 2 e (1)
2 H+ + 2e ! H2 (2)
The overall reaction is a spontaneous reaction :
Me + 2 H+ ! Me2+ + H2 (3)
because protons are an oxidizing reagent.
Because electrons are set free by the anodic reaction and absorbed by the cathodic reaction
the current flowing into the cathodic reaction must be equal (and opposite in sign) to the
current flowing out of the anodic reaction.
In the case of general corrosion the area of the cathodic and anodic sites is the same and
thus the current densities are equal.
The rate determining step of metal oxidation (e.g. iron) and proton reduction is the charge
transfer. The corrosion rate (corrosion current density J) and the corrosion potential can be
determined as shown in Figure 5103.01.01.
Fe ! Fe2++ 2e (1)
2 H+ + 2 e ! H2 (2)
_________________________
Fe + 2 H+ ! Fe2+ + H2
TALAT 5103 3
4. 0
Fe Fe2+ (1) E0 = -0.41 V
0
2H+ + 2e H2 (2) E0 = 0 V
∆E0 = 0.41 V
+ 2+ 0
Fe + 2H Fe +H2
E
1
H2 EO
2
- Fe2+ Ecor
2e 2
OH-
+
2H E O1
Log J
Log JCor
alu
Corrosion in Acid Solutions 5103.01.01
Training in Aluminium Application Technologies
Corrosion in Neutral Solutions
As protons, oxygen can corrode iron :
Fe ! Fe2+ + 2 e
O2 + 4 H+ + 4 e ! 2 H2O
________________________________
2 Fe + O2 + 4 H+ ! 2 Fe2+ + 2 H2O
Due to the low oxygen concentration in aqueous solution in equilibrium with the
atmosphere the kinetic of oxygen reduction is controlled by mass transport and thus also
the corrosion rate (Figure 5103.01.02).
0
E0 = -0.41 V
Fe Fe2+ + 2 e
E0pH= 0 V
O2 + 4 H+ + 4 e 2 H2O
∆E0 = 1.2 V
0
2 Fe + O2 + 4 H+ 2 Fe2+ + 2 H2O
2e
Fe2+
H2O
O2
Ecor
OH- E O1
2e Fe 2+
EO Log J
2 Log J
cor
alu
Corrosion in Neutral Solutions 5103.01.02
Training in Aluminium Application Technologies
TALAT 5103 4
5. Passivation
A metal can be passivated chemically (spontaneous formation of alumina on aluminium)
or electrochemically (metal corrosion products form an insoluble salt or hydroxide at the
metal surface). Figure 5103.01.03 shows a polarization curve of a metal undergoing an
active passive transition.
Figure 5103.01.04 shows the impact of various cathodic reactions on the corrosion current
and potential for a metal capable of undergoing an active passive transition.
Polarization Curve
E
D
AB Corrosion
C Beginning Passivation
CD Passive Transition
C
>D Oxygen Evolution
B
A
log J
alu
Training in Aluminium Application Technologies
Polarization Curve 5103.01.03
Corrosion Rate
E
3
3 Passivation
2 Passivation or Corrosion
1 Corrosion
2
1
log J
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Corrosion Rate 5103.01.04
Training in Aluminium Application Technologies
TALAT 5103 5
6. Corrosion of Aluminium and Aluminium Alloys
Aluminium is a thermodynamically reactive metal but it owes its excellent corrosion
resistance to the natural formation of a thin but very stable oxide film (Figure
5103.01.05).
In neutral aqueous solutions (4 < pH < 9) a 50 Å thick oxide film protects the metal
(passivation). Only in a very acid solution aluminium is homogeneously corroded by
forming Al3+ and in alkaline solution with formation of aluminates (AlO2 -). The
resistance and stability of the oxide layer is a function of the environment and alloy
composition and of the microstructure of the metal (influenced by heat treatments).
In order to maintain the excellent corrosion resistance of aluminium alloys it is necessary
to take into account a certain number of precautions. Some kinds of localized corrosion
can occur if the metal is used in unfavourable conditions. Some of the most important
cases of corrosion will be discussed and preventive methods will be mentioned.
Potential - pH Diagram according to Pourbaix
for Aluminium at 25 °C with an Oxide Film
E(V)
1.5 Passivity
1.0 O2/H
2 O
3+
Al
0.5
Al2O3 . 3H2O
-
Al O2
0
H+/H
-0.5
2 Corrosion
Corrosion
Passivity
-1.0
3+
Al Al O
-
2
-1.5 Al2O3
-2.0 Al
Immunity
-2.5
pH -2 -1 0 1 2 3 4 5 6 7 8 9 1011 13 15
12 14
alu
Potential - pH Diagram for Aluminium 5103.01.05
TALAT 5103 6
7. 5103.02 Localized Corrosion
• Environmentally influenced corrosion
− Pitting corrosion
− Crevice corrosion
− Filiform corrosion
− Biological corrosion
• Metallurgically influenced corrosion
− Galvanic corrosion
− Intergranular corrosion
• Mechanically assisted degradation
− Erosion
− Fretting corrosion
− Corrosion fatigue
• Environmentally induced cracking
− Stress corrosion cracking
− Hydrogen embrittlement
Environmentally Influenced Corrosion
Pitting Corrosion
In aerated aqueous solutions and in the presence of Cl- ions random formation of pits can
be observed at defects in the protected oxide film. Pitting develops only at potentials more
cathodic than the pitting potential Ep (Figure 5103.02.01). The intersection of the anodic
curve for aluminium (solid line) with a curve for the applicable cathodic reaction (one of
the representative dashed lines) determines the potential to which the aluminium is
polarized, either by cathodic reaction on the aluminium itself or on another metal
electrically connected to it. The potential to which the aluminium is polarized by a specific
cathode reaction determines corrosion current density and corrosion rate.
Typical Anodic Polarization Curve for Aluminium (Solid Line)
E
Ep
J
Typical Anodic Polarization Curve for Aluminium
alu
5103.02.01
Training in Aluminium Application Technologies (Solid Line)
The potential above which pits will initiate (Ep) decreases with an increase of the Cl-
TALAT 5103 7
8. concentration. However, only when cathodic reactions can occur (high enough
concentration of O2, low overpotential) pitting corrosion of aluminium starts.
Figure 5103.02.02 shows that the pit growth on the aluminium surface can be stimulated
by different reactions :
• within the corrosion pit and preventing repassivation :
− enrichment of Cl- ions;
− generation of an acid solution;
− limited O2 supply;
• in the pit mouth :
− formation of crust;
• around the pit :
− passivation;
− deposition of more noble metals.
Electrochemical mechanism of pit growth on Aluminium,
showing its autocatalytic self-stimulating nature
Cl-
Al2O3 Al3+ + 3 Cl- AlCl3 O2 + H2O + 4 e 4 OH-
+ +
Al3+ + H2O + Cl-
H+ + AlOHCl+
Al + 3 H+ + 2 Cl- 3/2 H2 + AlCl2+
Al Al3+ + 3 e
alu
Electrochemical Mechanism of Pit Growth 5103.02.02
Training in Aluminium Application Technologies
Very high purity aluminium (1099) has excellent resistance to pitting. Among commercial
alloys, the aluminium-magnesium alloys (5xxx) have the lowest pitting probability and
penetration rates. With low (< 0.04 %) copper content aluminium-manganese (3xxx)
alloys show comparable pitting behaviour. In aluminium-magnesium-silicon (6xxx) alloys
pitting is combined with intergranular corrosion. Aluminium-copper (2xxx) and
aluminium-zinc-magnesium-copper (7xxx) alloys are normally clad to protect against
pitting.
TALAT 5103 8
9. Crevice Corrosion
A very general method to improve the corrosion resistance of metals is to avoid the
presence of narrow openings or spaces between metal to metal or non-metal to metal
components. Localized corrosion at these sites will start due to the formation of an oxygen
differential cell. The corrosion in the crevice will be accelerated by an acidification due to
hydrolysis.
The factors affecting crevice corrosion are :
Geometrical factors:
type of crevice (metal-metal, metal-non metal)
crevice tightness
crevice depth
exterior-interior surface area ratio
Environmental factors:
bulk solution (O2, pH, T, Cl-)
mass transport
crevice solution (hydrolysis equilibria)
biological factors
Electrochemical reactions :
metal dissolution
O2 reduction
H2 evolution
Metallurgical factors:
alloys composition
passive film characteristics.
To prevent crevice corrosion some precautions must be taken :
When crevice corrosion is considered possible, the crevice should be sealed with a non
hardening elastomer to prevent the entry of moisture. Some sealants become hard and
crack on aging, allowing moisture to enter. The elastomeric requirement is essential for
joints in equipment that work in service, such as in all types of vehicles - road transport,
ships, and airplanes. There are two general types of sealant:
(1) one-component systems such as butyls or silicones, and
(2) two-component systems such as polysulfides and epoxies.
To prevent poultice corrosion which is a special case of crevice corrosion, the contact of
the bare aluminium surface with moisture-absorbing materials such as paper, cloth, wood,
asbestos, and noncellular foams should be avoided.
TALAT 5103 9
10. Filiform Corrosion
Filiform corrosion is another case of localized corrosion that may occur on an aluminium
surface under an organic coating. It takes the form of randomly distributed thread-like
filaments, and is sometimes called vermiform or warm track corrosion.
Aluminium is susceptible to filiform corrosion in a relative humidity range of 75 to 90%
with temperatures between 20 to 40°C. Typical filament growth rates average about 0.1
mm/d. Filament width varies with increasing humidity from 0.3 to 3 mm. The depth of
penetration in aluminium can be as deep as 15µ. Numerous coating systems used on
aluminium are susceptible to filiform corrosion, including nitrocellulose epoxy,
polyurethane, alkyd, phenoxy and vinyls. Condensates containing chloride, bromide,
sulphate, carbonate and nitrate ions stimulate filiform corrosion.
Filiform corrosion is an oxygen concentration cell in which the anodic active area is the
head of the filament and the cathode is the area surrounding it, including the tail (Figure
5103.02.03). At the head pH values as low as 1.5 to 2.5 have been reported.
Aqueous Acidic Cracked or
Middle of Tail Porous End
Solution
H2O H
+
OH-
Ionic- Zone of Precipitation and Expansion
drift (Corrosion Products)
Cl- H+ OH-
Active Trailing Tail
Head
H2O O2 H2O Coating
O2
Al2O3 + H2O
H+ Al(OH)3 Al(OH)3
Al3+ H2O OH-
Al Al
Al Al3+ + 3e 3 /4 O2 + 3/2 H2O + 3e 3 OH- 2Al(OH)3 Al2O3 + 3H2O
H+ + e /2 H2
1 Al3+ + 3OH- Al(OH)3
alu
Schematic Process of Filiform Corrosion in Aluminium 5103.02.03
Training in Aluminium Application Technologies
Anodic reaction produces Al3+ which react to form insoluble precipitates with the
hydroxyl (OH-) ions produced in the oxygen reduction reaction occurring in the tail.
Phosphate coatings or chromium containing conversion coatings applied to the metal
surface prior to organic coating are widely used to protect against filiform corrosion but
they are not always completely successful.
TALAT 5103 10
11. Biological Corrosion
Biological organisms are present in virtually all natural aqueous environments and can
attack and grow on the surface of structural materials, resulting in the formation of a
biological film or biofilm. The presence of a biological film does not introduce some new
type of corrosion, but it influences the occurrence and/or the rate of known types of
corrosion, e.g.:
increase or decrease of the corrosion rate due to oxygen reduction;
production of different aeration or chemical concentration cells;
production of organic and inorganic acids as metabolic by-products;
production of sulfides under anaerobic conditions.
For example, pitting corrosion of integral wing aluminum fuel tanks in aircraft that use
kerosene-base fuels has been known to occur. The attack proceeds under microbial
deposits in the water phase and at the fuel/ water interface. The organisms grow either in
continuous mats or sludges, or in volcanolike tubercules with gas bubbling from the center
(Figure 5103.02.04).
Biological Corrosion: Microbial Deposit
in the Form of Volcanolike Tubercles
Tubercle
4 Al(OH)3
1,5 O2 + 3 H2O + 6e 6(OH)- 4 Al3+ 6(OH)- 6e + 3 H2O + 1,5 O2
Cathode Cathode
Anode
4 Al
Biological Corrosion: Microbial Deposit
alu
5103.02.04
Training in Aluminium Application Technologies in the Form of Volcanolike Tubercles
The organisms commonly held responsible are Pseudomonas, Cladosporium and
Desulfovibrio. Cladosporium resinae produces a variety of organic acids (pH 3-4) and
metabolizes certain fuel constituents. These organisms may also act with the slime
forming Pseudomonads to produce oxygen concentration cells under the deposit.
Control of this type of attack has usually focused on a combination of reducing the water
content of fuel tanks, coating and using biocides and fuel additives.
TALAT 5103 11
12. Metallurgically Influenced Corrosion
Galvanic Corrosion
Due to the fact that different metals must be used very often electrically coupled in an
integrated structure a corrosion cell can occur resulting in acceleration of the corrosion
process in less resistant metals.
Figure 5103.02.05 gives the galvanic series of aluminium alloys and other metals in a
NaCl solution. This galvanic series, however, is not necessarily valid in non saline
solutions. For example aluminium is anodic to zinc in an aqueous 1 M sodium chromate
(Na2CrO4) solution and cathodic to iron in an aqueous 1 M sodium sulfate solution
(Na2SO4). Under most environmental conditions, aluminium and its alloys are the anodes
in galvanic cells with most other metals, protecting them by corroding sacrificially.
Contact of aluminium with more cathodic metals results in an increase of the potential of
aluminium; this must be avoided in any environment in which aluminium itself is subject
to pitting corrosion.
Metal Corrosion Potential (V/ SCE)
Magnesium -1.65
Zinc -1.02
Aluminium Alloys 7072 .0.88
Aluminium Alloys 5xxx -0.77 - -0.79
Aluminium Alloys 7075-T3 -0.76
Aluminium Alloys 1XXX, 3xxx, 6xxx -0.72 - -0.75
Cadmium -0.74
Aluminium Alloys 2024-T6 -0.73
Low-Carbon Steel, Cast and Wrought Iron -0.50
Lead -0.47
Tin -0.41
Lead-Tin Solder (60-40) -0.37
Brass (60-40) -0.20
Copper -0.12
Inconel -0.04
Stainless Steel (19-8, passive) -0.01
Bronze (95-5) +0.00
Nickel +0.01
Monel +0.02
alu
Galvanic Series of Metals in NaCl Solutions 5103.02.05
Training in Aluminium Application Technologies
To prevent the galvanic corrosion some precautions must be taken:
• Low potential difference (< 50 mV)
• High ratio area anode-cathode; e.g. stainless steel bolts in bare aluminium structures
• Low conductivity of the corrosion medium
• Slow kinetic of cathodic reduction, e.g. by inhibitors in closed loop circuits
Of course, without aqueous environment and without oxydants (O2) no galvanic corrosion
can start.
The galvanic corrosion can occur after deposition of heavy metals on aluminium.
Reduction of only a small amount of these ions can lead to severe localized corrosion. The
influence of Cu, Pb, Hg, Ni and Sn is very important in acidic solutions. A Cu2+
TALAT 5103 12
13. concentration of 0.02-0.05 ppm in neutral or acidic solutions is generally considered to be
the threshold value for initiation of Al pitting. This value is a function of the pH value and
the concentration of Cl-, HCO3 - and Ca2+.
Intergranular Corrosion
Galvanic corrosion can occur on the macroscopic but also on microscopic level.
Intergranular corrosion is a form of localized surface attack in which a narrow path is
corroded preferentially along the grain boundaries of a metal. The driving force is a
difference in corrosion potential that develops between a thin grain boundary zone and the
bulk of the immediately adjacent grains.
In the 2 xxx series alloys the anodic path is a narrow band on either side of the boundary
that is depleted in copper; in the 5xxx series alloys MgAl3 is anodic to aluminium and is
preferentially dissolved when the constituent forms a continuous path along grain
boundaries; copper free 7xxx series alloys are Zn and Mg - bearing constituents on the
grain boundary and generally considered to be the anodic. In the copper bearing 7xxx
series alloys, it appears to be the copper depleted bands along the grain boundaries, which
cause intergranular corrosion. The 6xxx series alloys generally resist this type of corrosion,
if the Si-content is kept at values near the stoichiometric Mg2Si composition or below.
Mechanically Assisted Degradation
Erosion
In noncorrosive environments, such as high purity water, the stronger aluminum alloys
have the greatest resistance to erosion-corrosion because resistance is controlled almost
entirely by the mechanical components of the system. In a corrosive environment, such as
seawater, the corrosion component becomes the controlling factor; thus, resistance may be
greater for the more corrosion-resistant alloys even though they are lower in strength.
Corrosion inhibitors and cathodic protection have been used to minimize erosion-
corrosion, impingement, and cavitation on aluminum alloys.
Figure 5103.02.06 illustrates the mechanism for growth of erosion corrosion pits.
TALAT 5103 13
14. Turbulent Eddy Mechanism for Growth of
Erosion Corrosion Pit
(a) (b)
(c) (d)
alu Turbulent Eddy Mechanism for Growth of 5103.02.06
Training in Aluminium Application Technologies Erosion Corrosion Pit
Fretting Corrosion
Fretting corrosion is a combined wear and corrosion process in which material is removed
from the contacting surface when motion between the surfaces is restricted to very small
amplitude oscillation.
Factors affecting fretting are:
contact load
amplitude
frequency
number of cycles
relative humidity
temperature
Corrosion Fatigue
Fatigue strengths of aluminum alloys are lower in such corrosive environments as
seawater and other salt solutions than in air, especially when evaluated by low-stress long-
duration tests. Such corrosive environments cause smaller reductions in fatigue strength in
the more corrosion-resistant alloys, such as the 5xxx and 6xxx series, than in less resistant
alloys, such as the 2xxx and 7xxx series.
Like SCC of aluminum alloys, corrosion fatigue requires the presence of water. In contrast
to SCC, however, corrosion fatigue is not appreciably affected by test direction with
respect to the rolling, forging or extrusion direction, because the fracture that results from
this type of attack is predominantly transgranular.
TALAT 5103 14
15. Environmentally Induced Cracking
Stress Corrosion Cracking (SCC)
SCC is a complex mechanism involving metallurgical, mechanical and environmental
parameters. SCC in aluminium alloys is characteristically intergranular. According to the
electrochemical theory, this requires a condition along the grain boundaries that makes
them anodic to the rest of the microstructure so that corrosion propagates selectively along
them.
This theory is confirmed by the fact that cathodic protection retards or eliminates SCC.
Parameters :
• magnitude and duration of tensile strength acting at the surface;
• residual stresses during quenching;
• grain structure and stress direction (resistance in short transverse direction
controls applications of products);
-
• environment : Cl and a decrease of the pH-value accelerate the attack.
The SCC of high-strength aluminium alloys such as 2024, 7075 and 7079 is often caused
by sustained residual or assembly tension stresses acting in the short transverse direction.
The stresses developed by service loads are usually intermittent and are designed to
operate in a favorable direction (longitudinal or long transverse) relative to the grain
structure.
The following guidelines should be considered by the designer to minimize SCC :
• select alloys and tempers that are resistant to SCC;
• use stress-relieved parts;
• perform forming and straightening on freshly quenched material, W-temper, to
ensure less severe effects;
• machine exterior surfaces before heat treating, because quenching causes more
desirable compressive surface stresses;
• machine internal surfaces after heat treating to partially remove internal
stresses;
• avoid fitup stresses by careful attention to tolerance. Poorly fitted parts and
misaligned parts should not be forced into place.
• Where built-in surface tensile stresses cannot be avoided, techniques such as
shot peening and surface rolling, or thermal stress relief from second stage
ageing, can be utilized to reduce the undesired stresses.
• postweld heat treat weldments.
TALAT 5103 15
16. Hydrogen Embrittlement
Hydrogen embrittlement is a form of environmentally assisted failure that results most
often from the combined action of hydrogen and residual or applied tensile stress.
Only recently it has been found that hydrogen embrittles aluminium. For many years, all
environmental cracking of aluminium and its alloys was represented as SCC. Hydrogen
damage in aluminium alloys may take the form of intergranular or transgranular cracking
or blistering. Hydrogen diffuses into the aluminium lattice and collects at internal defects
(e.g. during annealing of solution treating in air furnaces prior to age hardening).
Dry hydrogen gas is not detrimental to aluminium alloys; however, with the addition of
water vapor, subcritical crack growth increases dramatically.
The threshold stress intensity of cracking of aluminium also decreases significantly in the
presence of humid hydrogen gas at ambient temperature.
Hydrogen embrittlement of the 7000 series has been more intensively studied.
5103.03 Corrosion Prevention
• Alloy and temper selection
• Design of equipment
• Organic coating
• Inhibitors
• Anorganic surface treatments
• Cathodic protection
A number of corrosion preventives measures, special to specific types of aluminium
corrosion, have already been mentioned. This section deals with the main methods of
preventing corrosion of aluminium equipment :
• alloy and temper selection
• design of equipment
• organic coating (and sealants)
• inhibitors
• cathodic protection
• surface treatment
• modification of the environment
TALAT 5103 16
17. Alloy and Temper Selection
The choice of an aluminium alloy for a given use is often based on strength, formability,
ease of welding, or product availability. However, corrosion resistance must be included
when making the choice.
In general, aluminium-magnesium alloys (5xxx) have the best corrosion resistance,
followed by commercial-purity alloys (1xxx), aluminium-manganese alloys (3xxx), and
aluminium-magnesium-silicon alloys (6xxx) in that order, with only small differences
within families. These alloy families are normally used without protection although they
are sometimes painted (sidings for buildings) or anodized (window frames) for aesthetic
reasons. The aluminium-copper-magnesium alloys (2xxx) and the medium- and high-
strength aluminium-zinc-magnesium-copper alloys (7xxx) are usually given a protective
measure such as cladding or painting.
The importance of temper was mentioned previously. The H116 temper for 5083, 5086
and 5456 gives better resistance to intergranular and exfoliation corrosion. In 7xxx alloys,
the T7x temper provides improved resistance to SCC, for example, the T73 and T76
tempers of 7075 alloy. These tempers are a compromise, because strength is somewhat
lower than that of the T6 temper. The lower strength of these tempers in 7075 has been
offset by the development of stress-corrosion resistant tempers in 7049, 7050 and 7010
alloys.
Design of Equipment
The design of equipment can have an important influence on the corrosion behaviour,
even in environments in which aluminium is normally resistant.
Some guidelines can help the designer to minimize corrosion of aluminium in service :
• avoid contacts with dissimilar metals, but if they must be used, apply suitable
protection;
• avoid crevices, but if they must be present, and if thin sections are involved,
prevent ingress of moisture by application of sealants;
• join by continuous welding, rather than by skip welding or riveting;
• provide for complete draining and easy cleaning;
• avoid contact of bare aluminium surfaces with water-absorptive materials, but
if they must be used together, apply suitable protection;
• avoid sharp bends in piping systems;
• avoid heat transfer hot spots;
• avoid direct impingement by fluid streams;
• avoid excessive mechanical stress concentrations;
• when locating equipment, choose the least corrosive environment possible;
• eliminate sharp edges in equipment that is to be painted.
TALAT 5103 17
18. Organic Coating
Organic coating systems are frequently applied to aluminium for strictly decorative
purposes. But organic coatings may also be applied to aluminium for corrosion protection
in special situations. In both cases, adequate surface preparation (see Lectures 5201 and
5202) and careful coating selection (see Lecture 5204) are important to long coating life.
Most organic coatings provide corrosion protection by forming a physical barrier between
the aluminium surface and the environment. Some contain inhibitors such as chromate
primers. Aluminium insulation jacketing and refrigerator liners are coated on the back
with a vapor barrier to prevent poultice and crevice corrosion when condensation collects
between foamed insulation and the aluminium. Clear organic coatings are used where the
natural aluminium surface is desired and must be prevented. Temporary organic coatings
are sometimes used to protect aluminium surfaces from corrosion during storage and
transit. Heavy organic coatings, such as mastics and coal tars, are sometimes used to
protect aluminium surfaces that are embedded in soils and concrete.
The performance of organic coating systems can be maximized by following the specific
recommendations of suppliers regarding surface preparation, pretreatment, selection of
compatible conversion coat, primer and topcoat, application and curing. If continuing
maximum corrosion protection is required, the organic coating systems must be
maintained periodically.
Inhibitors
Inhibitors such as chromates that reduce the anodic corrosion reaction are termed anodic
inhibitors, whereas those (e.g. polyphosphates) reducing cathodic corrosion reaction are
termed cathodic inhibitors. If anodic inhibitors are used in an insufficient amount, they
tend to increase pitting. Cathodic inhibitors are safer in this respect. Mixed anodic and
cathodic inhibitor systems are also used.
Phosphates, silicates, nitrates, fluorides, benzoates, soluble oils and certain other
chemicals alone or in combination have been recommended for use with aluminium in
some services.
In mildly alkaline solutions the corrosion of aluminium can be inhibited by additions of
sodium silicate. Silicates with a high ratio of silicate to soda are widely used in alkaline
cleaning solutions, carbonates and phosphates. In mixed-metal, water-handling systems,
such as an automobile cooling system, inhibitors mixtures have been developed to prevent
corrosion of all metals in the system, including aluminium.
TALAT 5103 18
19. Anorganic Surface Treatments (see Lectures 5201, 5202 and 5205)
A number of chemical and electrochemical surface treatments can be used in order to
improve the corrosion resistance and/or the adhesion of organic coatings.
Cathodic Protection
The corrosion of a metal can be prevented by pushing down its potential (-1 to -1.2
Cu/CuSO4) into its immunity region. The current necessary to obtain this potential
decrease may be supplied by a sacrificial anode such as zinc or magnesium, by some
aluminium alloys (seawater only) or by an impressed current source (electrolysis cell using
an inert anode such as graphite or titanium). The magnitude of the current depends upon
the overpotential and resistance characteristics of the system to be protected.
5103.04 References/Literature
General :
Schreir, L.L.: "Corrosion I and II", Butherworths, 1979
Fontana, M.G.: "Corrosion Engineering", Mc. Graw Hill, 1988.
ASM (Ed.): "Metals Handbook", Vol. 13 "Corrosion"
Specific Aluminium:
ASM (Ed.): "Metals Handbook", Vol. 13 "Corrosion", p.583
Hatch, E.: "Aluminium : Properties and Physical Metallurgy", ASM, 1984, p. 242
Schreir, L.L.: "Corrosion I" , p.4.1, Butherworths, 1979
Hollingsworth, E.H., Hunsicker, H.Y. and Schweitzer, P.A.: Corrosion and Corrosion
Protection Handbook, Pt. Aluminium Alloys, pp.153-186, Marcel Dekker Inc., New
York and Basel, 1989
TALAT 5103 19
20. 5103.05 List of Figures
Figure No. Figure Title (Overhead)
5103.01.01 Corrosion in Acid Solutions
5103.01.02 Corrosion in Neutral Solutions
5103.01.03 Polarization Curve
5103.01.04 Corrosion Rate
5103.01.05 Potential - pH Diagram for Aluminium
5103.02.01 Typical Anodic Polarization Curve for Aluminium (solid line)
5103.02.02 Electrochemical Mechanism of Pit Growth
5103.02.03 Schematic Process of Filiform Corrosion in Aluminium
5103.02.04 Biological Corrosion: Microbial Deposit in the Form of Volcanolike
Tubercles
5103.02.05 Galvanic Series of Metals in NaCl Solutions
5103.02.06 Turbulent Eddy Mechanism for Growth of Erosion Corrosion Pit
TALAT 5103 20