This lecture describes important measures for the prevention of corrosion of unprotected, bare
aluminium. Basic knowledge of corrosion behaviour of aluminium and some knowledge of the electrochemical nature of corrosion is assumed
This lecture describes the processes of electroless, electrolytic, as well as physical and chemical vapour deposition of metals on the aluminium surface in order to achieve variations in its surface properties for functional and decorative purposes. Some knowledge of the surface properties of metals, metallurgy and electrochemistry of aluminium and familiarity with the subject matter covered in TALAT This lectures 5101, 5102, 5105 is assumed.
TALAT Lecture 5101: Surface Characteristics of Aluminium and Aluminium AlloysCORE-Materials
This lecture provides a realistic view of the aluminium surface in order to understand the need for "effective" surface treatment. Some knowledge in aluminium metallurgy is assumed.
TALAT Lecture 5105: Surface Treatment of AluminiumCORE-Materials
This lecture helps to understand the general principles, methods, properties and applications of plating on aluminium. Some knowledge in general electrochemistry is assumed.
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.
This lecture describes the key factors associated with conversion coatings on aluminium can be appreciated, such as general and local behaviour of the aluminium surface, range of conversion coatings and interrelationships, requirements of conversion coating, tailor-making of coatings, current and future issues. Some familiarity with the subject matter covered in TALAT This lectures 5101, 5102, 5201 is assumed.
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.
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.
TALAT Lecture 5102: Reactivity of the Aluminium Surface in Aqueous SolutionsCORE-Materials
This lecture provides better understanding of the electrochemistry of aluminium; it gives an introduction to the other lectures. Some knowledge in aluminium metallurgy, simple chemistry (thermodynamics and kinetics), electricity and general electrochemistry is assumed.
This lecture describes the processes of electroless, electrolytic, as well as physical and chemical vapour deposition of metals on the aluminium surface in order to achieve variations in its surface properties for functional and decorative purposes. Some knowledge of the surface properties of metals, metallurgy and electrochemistry of aluminium and familiarity with the subject matter covered in TALAT This lectures 5101, 5102, 5105 is assumed.
TALAT Lecture 5101: Surface Characteristics of Aluminium and Aluminium AlloysCORE-Materials
This lecture provides a realistic view of the aluminium surface in order to understand the need for "effective" surface treatment. Some knowledge in aluminium metallurgy is assumed.
TALAT Lecture 5105: Surface Treatment of AluminiumCORE-Materials
This lecture helps to understand the general principles, methods, properties and applications of plating on aluminium. Some knowledge in general electrochemistry is assumed.
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.
This lecture describes the key factors associated with conversion coatings on aluminium can be appreciated, such as general and local behaviour of the aluminium surface, range of conversion coatings and interrelationships, requirements of conversion coating, tailor-making of coatings, current and future issues. Some familiarity with the subject matter covered in TALAT This lectures 5101, 5102, 5201 is assumed.
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.
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.
TALAT Lecture 5102: Reactivity of the Aluminium Surface in Aqueous SolutionsCORE-Materials
This lecture provides better understanding of the electrochemistry of aluminium; it gives an introduction to the other lectures. Some knowledge in aluminium metallurgy, simple chemistry (thermodynamics and kinetics), electricity and general electrochemistry is assumed.
This document discusses various surface treatment and coating techniques, including conversion coatings like oxidation and anodizing, thermal coatings like carburizing and nitriding, metal coatings using electroplating and electroless deposition, vapor deposition methods like PVD and CVD, and organic coatings like paint and powder coating. It provides details on common processes, their applications and benefits, comparing techniques like electroless nickel plating versus hard chrome plating. The document emphasizes the importance of coatings for improving properties like corrosion and wear resistance.
This document discusses several industrial metals including iron, aluminum, vanadium, and titanium. It provides details on the production processes and uses of these metals. Specifically, it describes how iron is used as a catalyst in the Haber process to produce ammonia. It outlines the electrolytic process for producing primary aluminum from bauxite ore. The document discusses how vanadium is used as a catalyst in the contact process for producing sulfuric acid. Finally, it notes that titanium is used in jet engine and piping applications due to its strength and corrosion resistance.
The document summarizes key information about three materials: aluminum oxide, silicon carbide, and diamond. It discusses their crystal structures, properties like hardness and thermal conductivity, common processing methods, and applications. Aluminum oxide is used as an abrasive and refractory material. Silicon carbide is very hard and used for abrasives, armor, and power electronics. Diamond is the hardest known material and used in drilling, cutting, and jewelry due to its optical properties.
Surface Treatment of Aluminium by Anodizing: A Short ReviewIRJET Journal
The document summarizes the process of anodizing aluminum alloys. Anodizing involves electrochemically oxidizing the aluminum surface in an acid electrolyte bath to form a thicker, porous aluminum oxide layer for corrosion resistance. Key aspects of the process include: (1) the aluminum acts as the anode in the circuit and reacts to form aluminum ions that bond with oxygen to grow an oxide layer; (2) sulfuric acid is a commonly used electrolyte that produces a porous layer suitable for dyeing; and (3) sealing involves treatments that reduce porosity and prevent corrosion by sealing dye or lubricants inside the pores. Anodized aluminum has a variety of applications due to its enhanced corrosion resistance, ability to
The document discusses phosphating and chromating surface treatments. It describes the phosphating process as applying phosphoric acid to form a crystalline phosphate layer for corrosion resistance. The seven steps of the phosphating process are outlined. Chromating involves applying a hexavalent chromium solution to form a protective yellow-green layer and passivate metals like steel, aluminum, and zinc. The benefits of these processes are corrosion inhibition and providing an adhesive base for painting.
Aluminum anodizing: The study of the structure of the alumina layerSilio Moura
This work is focused on the study of the formation of an alumina (aluminum oxide) layer by double anodizing of aluminum. From this controlled oxidation method, a nanostructured porous layer with hexagonal cells was obtained. Ordered porous structures with 40-52 nm pore diameter were obtained by applying oxalic acid and a voltage-controlled procedure. The morphology of the surface and cross-section of the samples was analyzed by electron microscopy (Scanning and transmission). Finally, using this porous alumina as a template, Ni nanowires were obtained by electrochemical growth of the metal into the pores.
Surface coatings are used to protect metals from corrosion and improve their properties. Common coating methods include conversion coatings like oxidation, phosphatization and chromating which form protective oxide layers. Thermal treatments involve diffusion, carburizing and nitriding to enrich the surface. Metal coatings are applied by electroplating, electroless plating or metallizing. Vapor deposition techniques like PVD and CVD are used to deposit thin, hard coatings. Organic coatings such as paint provide decorative and protective functions. Coatings selection depends on the substrate material and desired properties.
Surface finishing is a broad range of industrial processes that alter the surface of a manufactured item to achieve a certain property.[1] Finishing processes may be employed to: improve appearance, adhesion or wettability, solderability, corrosion resistance, tarnish resistance, chemical resistance, wear resistance, hardness, modify electrical conductivity, remove burrs and other surface flaws, and control the surface friction.[1][2] In limited cases, some of these techniques can be used to restore original dimensions to salvage or repair an item. An unfinished surface is often called mill finish
Anodic aluminum oxide (AAO) is a self-organized material with a honeycomb-like structure of uniform, parallel nanopores formed through anodization of aluminum. The nanopores can range in diameter from 5 to several hundred nanometers. AAO was discovered in the 1930s but its porous structure attracted more interest for nanotechnology applications starting in the late 1980s due to its uniform nanostructure. AAO finds broad uses across fields like nanoelectronics, photonics, and bioanalysis.
The presentation covers various aspects of coating and deposition process in detail. The topics that are mainly covered in this PPT are
1) Type of Coating
2) Advantages and limitation for various coating process
3) Figures of various coating process
IMIDAZOLINE_901 Series Brochure_Chemtex_Jan20Debabrata Bose
This document provides information on Chemtex 901 Series imidazolines, which are thermally stable organic corrosion inhibitors used in various industrial applications. As cationic surfactants derived from fatty acids and amines, imidazolines can solubilize in nonpolar solvents and disperse in aqueous systems. They form protective films that inhibit corrosion through chemical and physical adsorption to metal surfaces. Chemtex 901 Series imidazolines have properties making them suitable as corrosion inhibitors, emulsifiers, thickeners, and more. They show effectiveness against various acids when used in concentrations of 0.1-2.0%. The document discusses the chemistry, applications, specifications, and safety of Chemtex's imidaz
Anodizing is an electrochemical process that converts the surface of metals like aluminum into a decorative, durable, corrosion-resistant finish through controlled oxidation. The metal acts as an anode in an electrolytic solution, forming a hard oxide layer on its surface. Depending on the process, this layer can be thicker than the natural oxide and provides benefits like improved aesthetics, hardness, and longevity. Common applications of anodized aluminum include architectural elements, appliances, vehicles, and aerospace and electronic components.
ORGANIC COATINGS FOR CORROSION PROTECTION OF TRANSFORMERS IN UNDERGROUND CHAM...Adriana de Araujo
Underground electrical transformers are frequently submitted to a very aggressive environment because of the stagnated water of underground chambers which is heated and contaminated. In Brazil, carbon steel structures of underground transformers are usually protected with coal tar epoxy paints in order to ensure their reliability. However, the use of this type of paints is being strongly restricted because coal tar contains complex mixtures of polycyclic aromatic hydrocarbons which contain many toxic and potentially carcinogenic substances. Aiming at replacing coal tar based paints by an environmentally friendly one; several paints were selected in the local market and submitted to performance tests in order to compare them with coal tar based paint. In addition, anodes were evaluated to study the application of galvanic cathodic protection in areas of metal exposure due to coating flaws. This paper presents and discusses the obtained results.
Os transformadores elétricos subterrâneos estão frequentemente expostos à corrosão intensa decorrente da estagnação de água aquecida e contaminada das câmaras subterrâneas. No Brasil, as estruturas de aço-carbono do transformador subterrâneo são usualmente protegidas com pintura de epóxi alcatrão de hulha que contém substâncias tóxicas e potencialmente cancerígenas. Com o objetivo de substituir as tintas à base de alcatrão de hulha por tintas ecologicamente corretas, tintas disponíveis no mercado nacional foram selecionadas e submetidas a ensaios de desempenho para a sua comparação com a tinta de alcatrão de hulha. Além disso, anodos foram avaliados para o estudo da aplicação de proteção catódica galvânica do metal exposto em áreas de falhas do revestimento. Este artigo apresenta e discute os resultados obtidos.
ARAUJO, A.; PANOSSIAN, Z; ALMEIDA, N.L; MARTINS, M.C.; JUNIOR, S.D.A. Organic coatings for corrosion protection of transformers in underground chambers. In: NACE INTERNATIONAL CONFERENCE & EXPO, 2012, Salt Lake City, Proceedings... Salt Lake City: NACE 2012.
This document summarizes information about an industrial company that started in 2014 and supplies both industrial and non-industrial products. Its industrial products include steel, aluminum, petrochemicals like polyethylene, bitumen, and gasoil. Its non-industrial products include saffron, berberis, and Persian carpets. It then provides details on the specifications and uses of various grades of bitumen, polyethylene products, and information about berberis and saffron.
The document summarizes chromium-free pre-treatment processes for aluminium as alternatives to chromate conversion coatings. It describes several processes including those based on molybdate, permanganate, phosphate, and titanium/zirconium, as well as cerium-based processes, silane treatments, and anodizing. Each process is outlined briefly, noting advantages such as corrosion protection and adhesion, as well as limitations regarding color, thickness, or variability in performance between alloy types. Health, environmental and regulatory concerns with chromate and other hazardous chemicals like hydrofluoric acid are also summarized.
Surface Processing Operation includes material surface cleaning and surface treating processes which is physically and/or chemically to alter surface texture, Mechanical properties, Physical properties, Chemical Properties etc, to have a better material.
This document summarizes key information about alumina ceramics:
1. Alumina is derived from bauxite ore and has important uses as a catalyst or catalyst support due to its high surface area and chemical resistance.
2. Alumina membranes can be fabricated through anodization of aluminum, sol-gel processing, or slipcasting. They are used for microfiltration, ultrafiltration, and gas separation.
3. Alumina membranes have applications in water treatment, food and beverage processing, and catalytic reactors due to their mechanical strength, thermal stability, and ability to selectively separate molecules and ions.
Concrete is today’s main building material. Modern infrastructure, road and bridge construction would be inconceivable without concrete as would skyscrapers and industrial buildings. Concrete is a versatile building material used especially in civil engineering in combination with steel. Concrete and reinforced concrete are building materials that have significantly changed construction. Despite concrete’s durability, serious concrete damage that endangers a building’s existence frequently occurs. The main cause of concrete damage is reinforcement steel corrosion due to environmental influences.
Powder’s Morphology and Cross-sectional SEM Images for Nickel based hard coat...Venkataraman Bandaru
This document discusses nickel-based hard coatings for wear, oxidation, and corrosion protection. It provides information on powder production methods, including water or gas atomization, fused or sintered and crushed powders, agglomerated and sintered powders, clad powders, and blend powders. It also discusses various powder materials like pure metals, alloys, superalloys, and carbides, providing examples of each along with SEM images of their powder cross-sections. The coatings are intended to improve surface properties and provide protection in industrial applications.
Copper is one of the most electrically conductive metal elements. It has a characteristic reddish-brown color and is very ductile and malleable. These properties, along with its high thermal and electrical conductivity, make copper useful for electrical wiring, plumbing, and cookware. Common copper alloys include brass and bronze, which are used for applications requiring corrosion resistance, strength, or specific colors.
TALAT Lecture 4205: Testing Methods for Welded JointsCORE-Materials
This lecture gives information about the relevant non-destructive and destructive testing methods for aluminium welded joints. Background in production welding and quality assurance is assumed.
This document discusses various surface treatment and coating techniques, including conversion coatings like oxidation and anodizing, thermal coatings like carburizing and nitriding, metal coatings using electroplating and electroless deposition, vapor deposition methods like PVD and CVD, and organic coatings like paint and powder coating. It provides details on common processes, their applications and benefits, comparing techniques like electroless nickel plating versus hard chrome plating. The document emphasizes the importance of coatings for improving properties like corrosion and wear resistance.
This document discusses several industrial metals including iron, aluminum, vanadium, and titanium. It provides details on the production processes and uses of these metals. Specifically, it describes how iron is used as a catalyst in the Haber process to produce ammonia. It outlines the electrolytic process for producing primary aluminum from bauxite ore. The document discusses how vanadium is used as a catalyst in the contact process for producing sulfuric acid. Finally, it notes that titanium is used in jet engine and piping applications due to its strength and corrosion resistance.
The document summarizes key information about three materials: aluminum oxide, silicon carbide, and diamond. It discusses their crystal structures, properties like hardness and thermal conductivity, common processing methods, and applications. Aluminum oxide is used as an abrasive and refractory material. Silicon carbide is very hard and used for abrasives, armor, and power electronics. Diamond is the hardest known material and used in drilling, cutting, and jewelry due to its optical properties.
Surface Treatment of Aluminium by Anodizing: A Short ReviewIRJET Journal
The document summarizes the process of anodizing aluminum alloys. Anodizing involves electrochemically oxidizing the aluminum surface in an acid electrolyte bath to form a thicker, porous aluminum oxide layer for corrosion resistance. Key aspects of the process include: (1) the aluminum acts as the anode in the circuit and reacts to form aluminum ions that bond with oxygen to grow an oxide layer; (2) sulfuric acid is a commonly used electrolyte that produces a porous layer suitable for dyeing; and (3) sealing involves treatments that reduce porosity and prevent corrosion by sealing dye or lubricants inside the pores. Anodized aluminum has a variety of applications due to its enhanced corrosion resistance, ability to
The document discusses phosphating and chromating surface treatments. It describes the phosphating process as applying phosphoric acid to form a crystalline phosphate layer for corrosion resistance. The seven steps of the phosphating process are outlined. Chromating involves applying a hexavalent chromium solution to form a protective yellow-green layer and passivate metals like steel, aluminum, and zinc. The benefits of these processes are corrosion inhibition and providing an adhesive base for painting.
Aluminum anodizing: The study of the structure of the alumina layerSilio Moura
This work is focused on the study of the formation of an alumina (aluminum oxide) layer by double anodizing of aluminum. From this controlled oxidation method, a nanostructured porous layer with hexagonal cells was obtained. Ordered porous structures with 40-52 nm pore diameter were obtained by applying oxalic acid and a voltage-controlled procedure. The morphology of the surface and cross-section of the samples was analyzed by electron microscopy (Scanning and transmission). Finally, using this porous alumina as a template, Ni nanowires were obtained by electrochemical growth of the metal into the pores.
Surface coatings are used to protect metals from corrosion and improve their properties. Common coating methods include conversion coatings like oxidation, phosphatization and chromating which form protective oxide layers. Thermal treatments involve diffusion, carburizing and nitriding to enrich the surface. Metal coatings are applied by electroplating, electroless plating or metallizing. Vapor deposition techniques like PVD and CVD are used to deposit thin, hard coatings. Organic coatings such as paint provide decorative and protective functions. Coatings selection depends on the substrate material and desired properties.
Surface finishing is a broad range of industrial processes that alter the surface of a manufactured item to achieve a certain property.[1] Finishing processes may be employed to: improve appearance, adhesion or wettability, solderability, corrosion resistance, tarnish resistance, chemical resistance, wear resistance, hardness, modify electrical conductivity, remove burrs and other surface flaws, and control the surface friction.[1][2] In limited cases, some of these techniques can be used to restore original dimensions to salvage or repair an item. An unfinished surface is often called mill finish
Anodic aluminum oxide (AAO) is a self-organized material with a honeycomb-like structure of uniform, parallel nanopores formed through anodization of aluminum. The nanopores can range in diameter from 5 to several hundred nanometers. AAO was discovered in the 1930s but its porous structure attracted more interest for nanotechnology applications starting in the late 1980s due to its uniform nanostructure. AAO finds broad uses across fields like nanoelectronics, photonics, and bioanalysis.
The presentation covers various aspects of coating and deposition process in detail. The topics that are mainly covered in this PPT are
1) Type of Coating
2) Advantages and limitation for various coating process
3) Figures of various coating process
IMIDAZOLINE_901 Series Brochure_Chemtex_Jan20Debabrata Bose
This document provides information on Chemtex 901 Series imidazolines, which are thermally stable organic corrosion inhibitors used in various industrial applications. As cationic surfactants derived from fatty acids and amines, imidazolines can solubilize in nonpolar solvents and disperse in aqueous systems. They form protective films that inhibit corrosion through chemical and physical adsorption to metal surfaces. Chemtex 901 Series imidazolines have properties making them suitable as corrosion inhibitors, emulsifiers, thickeners, and more. They show effectiveness against various acids when used in concentrations of 0.1-2.0%. The document discusses the chemistry, applications, specifications, and safety of Chemtex's imidaz
Anodizing is an electrochemical process that converts the surface of metals like aluminum into a decorative, durable, corrosion-resistant finish through controlled oxidation. The metal acts as an anode in an electrolytic solution, forming a hard oxide layer on its surface. Depending on the process, this layer can be thicker than the natural oxide and provides benefits like improved aesthetics, hardness, and longevity. Common applications of anodized aluminum include architectural elements, appliances, vehicles, and aerospace and electronic components.
ORGANIC COATINGS FOR CORROSION PROTECTION OF TRANSFORMERS IN UNDERGROUND CHAM...Adriana de Araujo
Underground electrical transformers are frequently submitted to a very aggressive environment because of the stagnated water of underground chambers which is heated and contaminated. In Brazil, carbon steel structures of underground transformers are usually protected with coal tar epoxy paints in order to ensure their reliability. However, the use of this type of paints is being strongly restricted because coal tar contains complex mixtures of polycyclic aromatic hydrocarbons which contain many toxic and potentially carcinogenic substances. Aiming at replacing coal tar based paints by an environmentally friendly one; several paints were selected in the local market and submitted to performance tests in order to compare them with coal tar based paint. In addition, anodes were evaluated to study the application of galvanic cathodic protection in areas of metal exposure due to coating flaws. This paper presents and discusses the obtained results.
Os transformadores elétricos subterrâneos estão frequentemente expostos à corrosão intensa decorrente da estagnação de água aquecida e contaminada das câmaras subterrâneas. No Brasil, as estruturas de aço-carbono do transformador subterrâneo são usualmente protegidas com pintura de epóxi alcatrão de hulha que contém substâncias tóxicas e potencialmente cancerígenas. Com o objetivo de substituir as tintas à base de alcatrão de hulha por tintas ecologicamente corretas, tintas disponíveis no mercado nacional foram selecionadas e submetidas a ensaios de desempenho para a sua comparação com a tinta de alcatrão de hulha. Além disso, anodos foram avaliados para o estudo da aplicação de proteção catódica galvânica do metal exposto em áreas de falhas do revestimento. Este artigo apresenta e discute os resultados obtidos.
ARAUJO, A.; PANOSSIAN, Z; ALMEIDA, N.L; MARTINS, M.C.; JUNIOR, S.D.A. Organic coatings for corrosion protection of transformers in underground chambers. In: NACE INTERNATIONAL CONFERENCE & EXPO, 2012, Salt Lake City, Proceedings... Salt Lake City: NACE 2012.
This document summarizes information about an industrial company that started in 2014 and supplies both industrial and non-industrial products. Its industrial products include steel, aluminum, petrochemicals like polyethylene, bitumen, and gasoil. Its non-industrial products include saffron, berberis, and Persian carpets. It then provides details on the specifications and uses of various grades of bitumen, polyethylene products, and information about berberis and saffron.
The document summarizes chromium-free pre-treatment processes for aluminium as alternatives to chromate conversion coatings. It describes several processes including those based on molybdate, permanganate, phosphate, and titanium/zirconium, as well as cerium-based processes, silane treatments, and anodizing. Each process is outlined briefly, noting advantages such as corrosion protection and adhesion, as well as limitations regarding color, thickness, or variability in performance between alloy types. Health, environmental and regulatory concerns with chromate and other hazardous chemicals like hydrofluoric acid are also summarized.
Surface Processing Operation includes material surface cleaning and surface treating processes which is physically and/or chemically to alter surface texture, Mechanical properties, Physical properties, Chemical Properties etc, to have a better material.
This document summarizes key information about alumina ceramics:
1. Alumina is derived from bauxite ore and has important uses as a catalyst or catalyst support due to its high surface area and chemical resistance.
2. Alumina membranes can be fabricated through anodization of aluminum, sol-gel processing, or slipcasting. They are used for microfiltration, ultrafiltration, and gas separation.
3. Alumina membranes have applications in water treatment, food and beverage processing, and catalytic reactors due to their mechanical strength, thermal stability, and ability to selectively separate molecules and ions.
Concrete is today’s main building material. Modern infrastructure, road and bridge construction would be inconceivable without concrete as would skyscrapers and industrial buildings. Concrete is a versatile building material used especially in civil engineering in combination with steel. Concrete and reinforced concrete are building materials that have significantly changed construction. Despite concrete’s durability, serious concrete damage that endangers a building’s existence frequently occurs. The main cause of concrete damage is reinforcement steel corrosion due to environmental influences.
Powder’s Morphology and Cross-sectional SEM Images for Nickel based hard coat...Venkataraman Bandaru
This document discusses nickel-based hard coatings for wear, oxidation, and corrosion protection. It provides information on powder production methods, including water or gas atomization, fused or sintered and crushed powders, agglomerated and sintered powders, clad powders, and blend powders. It also discusses various powder materials like pure metals, alloys, superalloys, and carbides, providing examples of each along with SEM images of their powder cross-sections. The coatings are intended to improve surface properties and provide protection in industrial applications.
Copper is one of the most electrically conductive metal elements. It has a characteristic reddish-brown color and is very ductile and malleable. These properties, along with its high thermal and electrical conductivity, make copper useful for electrical wiring, plumbing, and cookware. Common copper alloys include brass and bronze, which are used for applications requiring corrosion resistance, strength, or specific colors.
TALAT Lecture 4205: Testing Methods for Welded JointsCORE-Materials
This lecture gives information about the relevant non-destructive and destructive testing methods for aluminium welded joints. Background in production welding and quality assurance is assumed.
This lecture describes the fundamentals of bending and folding aluminium sheet; it also describes different methods in design of folding tools. Background in production engineering and sheet metal forming and familiarity with the subject matter covered in TALAT This lectures 3701- 3705 is assumed.
TALAT Lecture 4101: Definition and Classification of Mechanical Fastening Met...CORE-Materials
This document provides an overview of mechanical fastening methods for joining aluminum parts, including definitions and classifications. It discusses screw joints, folds, rivets, and clinching. Screw joints can be pierced, through, or blind holes. Folds are formed locking joints created through folding, interlocking, and pressing sheets together. Riveting includes indirect and direct methods. Blind rivets have a predetermined break point. The document aims to introduce the principal types of mechanical fastening methods for aluminum.
This document provides an overview of application characteristics for rivet and clinch joints. It discusses design considerations such as choosing rivet diameters and distances from edges. It also covers material and tooling parameters that influence joint quality like surface finish. Testing methods are described for shear-tensile, fatigue, and impact tests. Sample geometries and results are shown. Finally, it briefly discusses cost considerations for different joining technologies.
This lecture provides a background on aluminium alloys suitable for impact extrusion. It draws attention to raw material parameters which may affect the properties of impact extruded parts. Basic knowledge about the formability of metals and background in mechanical engineering is assumed.
TALAT Lecture 2301: Design of Members Example 4.4: Bending moment resistance ...CORE-Materials
This 3 sentence summary provides the key details about the document:
1) The document is a 10 page example from a lecture on designing members for bending moment that analyzes the bending moment resistance of a welded hollow section with outstands using a class 4 cross section.
2) It presents the geometry, material properties, nodes, and elements of the hollow cross section and performs iterative calculations of the effective cross section area, stress distribution, and effective thicknesses accounting for any heat affected zones to determine the bending moment resistance.
3) The example is considered comprehensive because it shows calculations in detail, covers all classes of cross sections, and demonstrates how to increase effective thickness for non-fully stressed elements through
TALAT Lecture 3503: Finishing and other Supplementary OperationsCORE-Materials
This lecture describes supplementary fabrication measures for impact extruded parts and gives some examples of finished impacts. Basic knowledge about the formability of metals and background in mechanical engineering is assumed.
TALAT Lecture 2301: Design of Members Example 5.5: Axial force resistance of ...CORE-Materials
This 3-page document provides an example calculation for determining the axial force resistance of a laced column. It includes dimensions, material properties, and calculations of various parameters needed for the analysis. Key steps and results are shown, such as determining the effective length, flexural buckling resistance, and checking that the lacing can resist the required shear force. In the end, it is determined that the lacing can adequately resist the applied axial load of 270 kN.
This lecture helps to understand how the properties of forgings evolve during the manufacturing process. General understanding of metallurgy and deformation processes is assumed.
This lecture describes fabrication processes for superplastic forming, i.e. female and male die forming, and the criteria for selecting the correct process. General background in production engineering and material science is assumed.
TALAT Lecture 3801: Manufacturing Examples and FundamentalsCORE-Materials
This lecture describes the fundamentals of the superplastic behaviour phenomenon of aluminium alloys and the basic process parameters which govern the manufacturing of superplastic sheet metal parts. General background in production engineering and material science is assumed.
This lecture describes the factors important for the quality assurance of adhesive joining; it gives information about the destructive and non-destructive testing methods for the quality control of adhesive joining. General background in production engineering and material science, some knowledge of mechanics and polymer science is assumed.
This lecture describes the detailed processes of single-step and multiple-step clinching; it shows the differences of the various clinching methods concerning the amount of shearing; it illustrates the major differences in mechanical properties of clinch joints compared with resistance spot welds. General mechanical engineering background and familiarity with the subject matter covered in TALAT This lecture 4101 is assumed.
TALAT Lecture 3505: Tools for Impact ExtrusionCORE-Materials
This lecture provides knowledge about design philosophy and tool materials for impact tools, which are a cost factor and eminently important for successful impact extrusion. Basic knowledge about the formability of metals and background in mechanical engineering is assumed.
TALAT Lecture 4107: General Summary and Future TrendsCORE-Materials
This lecture points out the need of data sources for designing mechanical joints; it describes concepts for FEM-Modelling of mechanical joints. General mechanical engineering background and familiarity with the subject matter covered in TALAT This lectures 4101- 4106 is assumed.
TALAT Lecture 4702: Factors Influencing the Strength of Adhesive JointsCORE-Materials
This lecture describes the factors governing the strength of adhesive joints in order to appreciate these factors for the design of adhesively bonded joints, i.e. geometry of joint, stiffness and strength of the adjoining parts, stress distribution in the adhesive layer as well as the effects of humidity and ageing. General background in production engineering and material science, some knowledge of mechanics and polymer science is assumed.
TALAT Lecture 4703: Design and Calculation of Adhesive JointsCORE-Materials
This lecture describes the basic types of loadings of adhesive joints and to give examples of recommended joint designs; it shows how to calculate the strength of adhesive joints. General background in production engineering and material science, some knowledge of mechanics and polymer science is assumed.
This lecture defines important terms of the process of stretch forming and it describes the basic processes of stretch forming. Background in production engineering and familiarity with the subject matter covered in TALAT This lecture 3701 is assumed.
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TALAT Lecture 5104: Basic Approaches to Prevent Corrosion of Aluminium
1. TALAT Lectures 5104
Basic Approaches to Prevent Corrosion of Aluminium
14 pages, 9 figures
Basic Level
prepared by J. Gazapo, INESPAL, Alicante
Objectives:
− to describe important measures for the prevention of corrosion of unprotected, bare
aluminium
Prerequisites:
− Basic knowledge of corrosion behaviour of aluminium; some knowledge of the
electrochemical nature of corrosion
Date of Issue: 1994
EAA - European Aluminium Association
2. 5104 Basic Approaches to Prevent Corrosion of
Aluminium
Table of Contents
5104 Basic Approaches to Prevent Corrosion of Aluminium...................2
5104.00 Introduction............................................................................................... 2
5104.01 Selection of Corrosion Resistant Alloys .................................................. 3
Wrought Aluminium Alloys ....................................................................................4
Cast Aluminium Alloys ...........................................................................................4
5104.02 Improvement in Equipment Design ........................................................ 5
Prevention of Galvanic Corrosion ...........................................................................5
Prevention of Deposition Corrosion ........................................................................7
Prevention of Crevice Corrosion .............................................................................8
Prevention of Stress Corrosion ................................................................................8
Stress Corrosion Resistant Tempers ........................................................................9
5104.03 Alteration of the Environment................................................................. 9
Corrosion Inhibitors ...............................................................................................10
5104.04 Cathodic Protection ................................................................................ 10
Sacrificial Anodes..................................................................................................12
Impressed Current ..................................................................................................12
Alclad Alloys .........................................................................................................13
Practical Case.........................................................................................................13
5104.05 Literature/References ............................................................................. 14
5104.06 List of Figures............................................................................................ 14
5104.00 Introduction
In general, aluminium alloys have good corrosion resistance in the following
environments: atmosphere, fresh water, seawater, most soils, most foods and many
chemicals. The term „good corrosion resistance“ means that in many cases aluminium
alloys can be used without surface protection and will give long service lifes. Depending
on the aggresiveness of the environment for a given application as well as on the function
of the product and the expected service requirements and life, measure may have to be
taken to prevent or limit the extent of corrosion attack. There are several options for
prevention measures (see Figure 5104.00.01) which can be adopted.
TALAT 5104 2
3. Optional Measures to Prevent Corrosion
Add Install Improve
Inhibitors Cathodic Protection Equipment Design
REMEDIAL
CORROSION MEASURES
Change Material Apply Alter Environment
Protective Coatings
alu
Optional Measures to Prevent Corrosion 5104.00.01
Training in Aluminium Application Technologies
In this lecture only those measures are treated which relate to unprotected aluminium
products and components. Protective surface treatments like pretreatments, painting and
anodizing are described in Lectures 5201, 5202, 5203 and 5204.
5104.01 Selection of Corrosion Resistant Alloys
The addition of alloying elements to aluminium affects the corrosion behaviour, and it is
important to select the most adequate alloy for each environment.
The mayor alloying elements used in aluminium alloys are: copper, magnesium,
manganese, silicon and zinc and the impurities in commercially pure aluminium are iron
and silicon (Figure 5104.01.01).
Copper reduces the corrosion resistance more than any other
alloying element
Iron reduces corrosion resistance and the content should be
kept low when maximum resistance to corrosion is needed
Magnesium has a beneficial effect on corrosion resistance
Manganese has a slightly beneficial effect on corrosion resistance
Silicon has a small detrimental effect on corrosion resistance
Zinc in most environments zinc has only a small effect on
corrosion resistance
alu Effects of Alloying Elements on Corrosion Resistance
5104.01.01
Training in Aluminium Application Technologies of Aluminium
TALAT 5104 3
4. Wrought Aluminium Alloys
Pure Aluminium (> 99,9 % Al)
Superpure aluminium (> 99,9 % Al) exhibits the best corrosion resistance possible with
aluminium by wide margin. Performance drops sharply with the introduction of impurities,
particularly copper and iron.
Al-Mn
The Al-Mn alloys have very good corrosion resistance and are used for outside
applications without protection.
Al-Mg
In general, the Al-Mg alloys have the best corrosion resistance of all the aluminium
alloys. Above 4% magnesium content, fabrication practice has a marked influence on their
long-term behaviour in corrosive environments, even at normal temperatures. After long
time exposures above 60° C the Mg-rich alloys may become susceptible to stress corrosion
cracking or exfoliation.
Al-Cu
Alloys containing appreciable amounts of copper (> 0,25%) have less corrosion
resistance, and should not be used in aggressive marine or industrial environments without
providing protective coatings. In the past one of the most common errors was to use Al-Cu
alloys in corrosive environments without adequate protective measures.
Al-Zn-Mg-Cu
Alloys containing Zn, Mg and Cu are similar in corrosion behaviour to the Al-Cu family
and also require protection in corrosive environments.
Al-Zn-Mg
For this family of alloys the fabrication practices, especially thermal treatments and the
composition of the alloy are critical factors in the corrosion.behaviour. Al-Zn-Mg alloys
may be sensitive to stress corrosion cracking and exfoliation.
Cast Aluminium Alloys
Corrosion of aluminium castings is usually less of a problem than with sheet products
since in general, the cross section is thicker and more surface corrosion can be tolerated.
Al-Mg casting alloys have a good general corrosion resistance and can be used in marine
environments.
The Al-Si are generally considered to have good corrosion resistance in atmospheres and
waters.
Al-Cu and Al-Si-Cu alloys require surface protection under corrosive conditions.
The behaviour of an alloy depends on the environment that it has to withstand; as an
TALAT 5104 4
5. example, the following table gives an idea of the behaviour of different alloys in acids and
alkalines (Figure 5104.01.02). The lower the rating the better the corrosion resistance.
5104.02 Improvement in Equipment Design
Since the corrosion behaviour of a metal is influenced by the physical and chemical
conditions of the environment (for example temperature, contaminants, differential
concentration, etc.) as well as by its chemical composition, the design can have
appreciable effect on the nature and rate of corrosion.
in Acids in Alkalines
Alloy Rating Alloy Rating
S.P.*) 6 7075-T6 7
1100-H16 24 7072 15
3003-H14 28 6053-T6 15
3003 Alclad 29 S.P. 17
7072 33 6061-T6 17
1050-H16 33 5052-H14 22
6063-T6 41 6063-T6 28
5052-H14 43 3003 Alclad 32
6053-T6 45 3003-H14 32
6061-T6 49 1100-H16 37
7075-T6 65 1050-H16 43
*) S.P. Super Purity Aluminium (> 99.99%)
alu
Behaviour of Different Alloys in Acids and Alkalines 5104.01.02
Training in Aluminium Application Technologies
The most common design failures encountered in service with aluminium structures
involves galvanic, crevice, deposition and stress corrosion.
In the following paragraphs a general recommendation to eliminate or at least reduce the
effect of these types of corrosion are given:
Prevention of Galvanic Corrosion
The following „rules“ can be suggested to minimize galvanic corrosion:
1. Select combinations of metals as close as possible in the galvanic series for the
environment being considered (Figure 5104.02.01).
2. Use cathodic fastenings. Avoid combinations with an unfavourable (small) ratio of
TALAT 5104 5
6. anode to cathode area (Figure 5104.02.02).
3. Provide complete electrical insulation of the two metals joined. This may be done by
using insulating gaskest, sleeves, etc. (Figure 5104.02.03).
4. If paint is applied, always paint the cathode. If only the anode is painted, a scratch
would give an unfavourable ratio of anode to cathode area, and lead to attack at the
scratch. Keep such coatings in good repair.
5. Increase the thickness of the anodic material. Alternatively, install small replaceable
heavy sections of the anodic metal at the joint.
6. Where possible, place the dissimilar metal contact out of the corrosive environment.
7. Were possible, avoid threaded joints in dissimilar couples as the threads will
detoriorate. Brazed or welded joints are preferred.
8. If possible, use corrosion inhibitors (e.g. in circulating systems).
9. In cases where the metals must remain in electrical contact through an external circuit,
design the equipment to keep the metals as far apart as possible to increase the
resistance of the liquid path (electrolyte).
10. If necessary and where possible, use cathodic protection with zinc or magnesium
sacrificial anodes.
11.Under the most aggressive conditions, only zinc, cadmium and magnesium can be
placed in contact with aluminium without causing galvanic corrosion.
Galvanic corrosion of aluminium in contact with varios
metals in marine, tropical and urban atmospheres
Marine Atmosphere Tropical Atmosphere
24 8 a: Zinc
% b: Cadmium
%
20 c: Tin
4 d: Monel (67% Ni, 30% Cu )
16 e: Nickel
f: Stainless steel
0
(18% Cr; 9% Ni)
12 a b cd e f g h i j k l m
g: Lead
h: Gold
8 i: Soft soldering alloy
Urban Atmosphere (= 60% Cu + 2% Pb)
4 4 j: Stainless steel (16% Cr)
k: Silver
%
l: Iron
0
0 m: Copper
a b cd e f g h i j k l m a b cd e f g h i j k l m
alu
Severity of Galvanic Corrosion in Various Atmosphers 5104.02.01
Training in Aluminium Application Technologies
TALAT 5104 6
7. Prevention of Deposition Corrosion
The following measures will help to reduce deposition corrosion on aluminium
1. Re-design to avoid precipitation of the more noble metal, e.g. through
drainage
2. Use Alclad aluminium
3. Use inhibitors
4. Paint the source of metal
5. Clean frequently to remove the deposited noble metal
Joints with Different Metals
Aluminium Steel
Steel Aluminium
(A) (B)
Not Correct Correct
alu Example of the Effect of Anode to Cathode Area on
5104.02.02
Training in Aluminium Application Technologies Corrosion of Bi-Metal Joints
TALAT 5104 7
8. Galvanic Corrosion
2H+ + 2e- H2 3+ -
Al Al + 3e
A - Copper
Aluminium
Assemblies "A" and "B"
B - Steel Aluminium cause galvanic corrosion,
Insulator Corrosion
the assembly "C" avoids it.
C - Steel Aluminium
Sleeve and
Insulator Insulating Washer
alu
Prevention of Contact Corrosion by Electrical Insulation 5104.02.03
Training in Aluminium Application Technologies
Prevention of Crevice Corrosion
In the design of aluminium structures exposed to a marine atmosphere for long periods of
time some measures should be taken to prevent crevice corrosion.
The following measures will help to reduce crevice corrosion in aluminium structures:
1. Cover the faying surfaces before assembly with an inhibitive paint system
2. Fill the crevice with a jointing compound or resilient gasket material to prevent
the ingress of moisture.
Prevention of Stress Corrosion
In the design of aluminium structures under permanent stress conditions some measures
should be taken into account in order to minimize stress corrosion.
The following measures will help to reduce the incidence of stress corrosion problems in
aluminium structures:
1. Ensure that an adequate cross section is used that will not be overstressed. Particular
attention must be paid to residual or assembly stresses that act in the short transverse
direction.
2. A good paint system which includes an inhibitive primer will offer some protection
again stress corrosion. However, it should be realized that paint coatings are not
completely impermeable to moisture and should not be expected to protect very
TALAT 5104 8
9. susceptible alloys.
3. Spray metallizing with some aluminium alloys will provide an appreciable measure of
protection against stress corrosion, which should be further improved by painting.
4. Surface working procedures, such as shot peening or surface burnishing to achieve a
compressive residual stress in the surface, when properly applied, have proven effective
as a means of reducing the incidence of stress corrosion cracking.
5. Applied stresses. Sustained applied surface tensile stresses, should not exceed the
following limits:
− in the longitudinal direction 50% yield stress,
− in the long transverse direction between 35 and 50% yield stress,
− in the short transverse direction: as low as possible and preferably not greater
than 15% of the yield stress.
Stress Corrosion Resistant Tempers
Certain of the high strength aluminium alloys systems respond to precipitation treatments
(over-ageing), which result in metallurgical conditions having significantly improved
stress corrosion resistance at little or no sacrifice in mechanical properties (T76, T73
tempers).
All the recommendations are general statements and a detailed study is necessary in each
case.
5104.03 Alteration of the Environment
Sometimes it is possible to reduce or eliminate the aggressiveness of an environment by
altering it in one way or another.
In some chemicals, for example phenol, the addition of a trace of water (e.g. 0,3%) will
prevent vigorous corrosion that would occur under anhydrous conditions. In others, for
example liquid sulphur dioxide, traces of water promote corrosion of aluminium.
In general, movement or turbulence, if not excessive, will sometimes prevent pitting that
might otherwise occur.
The adjustment of pH to the safe range (4.5 to 8.5) will prevent or reduce corrosion.
The deaeration of water will greatly reduce its pitting tendency toward aluminium.
Raising the temperature, in general, may increase the rate of general surface corrosion, but
has the beneficial tendency of reducing the rate of pitting corrosion.
Obviously, these effects are specific to individual conditions, and little more than general
statements such as the above can be made on this subject.
TALAT 5104 9
10. Corrosion Inhibitors
An inhibitor is a substance which when added (usually in a small amount) to a corrosive
liquid or chemical, reduces or prevents corrosion of a metal that would otherwise occur.
Inhibitors may affect the anodic corrosion reaction, in which case they are termed „anodic
inhibitors“, or they may inhibit the cathodic corrosion reaction in which case they are
termed „cathodic inhibitors“.
Anodic inhibitors can be dangerous if not added in sufficient amount, since while they
may reduce the effective anode area, attack at the remaining sites will be more severe than
in the absence of the inhibitor.
Cathodic inhibitores are safer since a partial reduction of the effective cathode area will
reduce corrosion at the anode. They are, however, usually less effective than anodic
inhibitors.
Chromate (in the form of sodium or potassium chromate or dichromate) is the most
commonly used inhibitor with aluminium and is an anodic type inhibitor. To prevent the
pitting of aluminium in aggressive water, the addition of 500 ppm. of sodium chromate or
dichromate with a pH adjusted to 8.5 is effective.
Phosphate, silicate, nitrate, nitrite, benzoate, soluble oils and other chemicals have also
been recommended alone or in combination to inhibit the corrosion of aluminium by
aggressive waters.
Inhibition of water is usually economic only in a recirculated, closed loop system. In a
mixed metal system including, for example aluminium and copper it is important to design
a good inhibitor system and maintain the pH above 8.0-8.5 to prevent copper dissolution
and their subsequent deposition on the aluminium. surface.
The complexity of the inhibition tends to make it difficult for a general engineer to
develop a satisfactory water treatment without the help of a specialist.
Frequently, laboratory testing on location is necessary to establish the best treatment.
5104.04 Cathodic Protection
The theory of cathodic protection of a buried metal is simple. A direct electric current is
caused to flow to the metal (generated by sacrificial anodes or impressed current) to be
protected.
TALAT 5104 10
11. The current polarizes the local cathode areas to the potential of the local anode and creates
an equi-potential surface. Thus local cell potential becomes zero and pitting does not
occur.
Soil
-
+
Electrode
Pipeline
alu Prevention of Corrosion through Cathodic Protection
5104.04.01
Training in Aluminium Application Technologies by Impressed DC Current
The current may be produced by a rectifier with a metal or graphite electrode
(Figure 5104.04.01) or by sacrificial galvanic anodes of magnesium or zinc
(Figure 5104.04.02).
Soil
Pipeline
Sacrificial Anode
alu Prevention of Corrosion through Cathodic Protection
5104.04.02
Training in Aluminium Application Technologies by Sacrifical Anodes
To reduce the amount of current required, the metal to be protected is sometimes coated
with a paint, protective tape or other wrapping material.
In the steel pipelime industry the technique of cathodic protection has been well
established and its effectiveness throughly demonstrated. Experience with buried
aluminium is limited to isolated experiments and a limited number of operating lines.
TALAT 5104 11
12. Sacrificial Anodes
Aluminium can be cathodically protected by coupling it to zinc or magnesium used as a
sacrifical anode.
In the case of aluminium probably the mechanism of protection consists of polarizing
cathodic impurities in the metal to the corrosion potential of passive aluminium
counteracting the detrimental effect of such impurities.
Zinc is able to serve as a sacrificial anode to aluminium in neutral or slightly acid media in
spite of the fact that aluminium is more active than zinc in the EMF series. In alkaline
media aluminium looses its passivity and becomes anodic to zinc.
Magnesium has been the material normally used to protect aluminium in some cases.
Corrosion has been stopped by the installation of magnesium anodes even in buried pipes
with accumulation of corrosion products. In some cases over-protection may result in
producing cathodic corrosion on the aluminium.
The potential generated between the magnesium anodes and aluminium normally does not
exceed -1.20 volts (Cu/CuSO4) and normally there is no evidence of cathodic corrosion
due to alkali formation.
Impressed Current
Cathodic protection by impressed current requires a source of direct current and auxiliary
electrode as shown in Figure 5104.04.01.
The D/C source is connected with the positive terminal to the auxiliary electrode, and the
negative terminal to the structure to be protected. The current flows from the electrode
through the electrolyte to the structure.
It is generally accepted that protection of aluminium is achieved when the potential of the
burried aluminium surface is maintained in the range -0.85 to -1.10 volts (Cu/CuSO4) and
then significant cathodic corrosion does not occur until a value of -1.20 volts is exceeded.
The chemical nature of the soil can affect the safe upper potential which in some cases can
be appreciably higher than -1.20volts.
The current density required depends on the environment but generally the applied current
density must always exceed the current density equivalent by the estimated or measured
corrosion rate (in tap water ca. 20 mA/m2, in soil an average of 5 mA/m2 can be estimated)
With the application of coatings on the aluminium the current density can be reduced and
it will be possible to protect a pipe of 20 Km with only 90-240 mA.
TALAT 5104 12
13. Alclad Alloys
Alclad aluminium is a duplex product consisting of a thin layer of one alloy integrally
bonded to a thicker core alloy. The cladding alloy is chosen as a sacrificial anode to protect
the core.
The alloys normally used as cladding materials for protection purposes are of the Al-Zn
family, in some cases, however, pure aluminium has been used.
The protection mechanism of the cladding products consists of galvanic protection. When
a pit reaches the core material, the cladding tends to corrode preferentially, while the core
remains unaffected (Figure 5104.04.03).
Cladding is a real possibility for extending the life of aluminium pipelines which carry a
product causing pitting corrosion of the metal.
Conventionally, the cladding on each side of sheet has been 5% of the total thickness of
the sheet.
Alclad Alloys
Protective current
Core Material Clad Layer
Al-Mn Al-Zn
alu Prevention of Corrosion of Al-Mn Core Material through
5104.04.03
Training in Aluminium Application Technologies Sacrificial Cladding with Al-Zn Alloy
Practical Case
How to minimize the pitting of aluminium by an aggressive water?
Here are four possible preventive measures that should be considered:
1. Use Alclad alloys
Use 3003 or 65S clad with 72S. This will not prevent pitting but it delays perforation by an
appreciable margin.
2. Increase wall thickness
TALAT 5104 13
14. Experience with large water storage tanks suggests that, provided the wall thickness is 6-7
mm perforation will no occur for a very long period of time (probably 50-100 years)
even though pitting does occur. This is because the rate of penetration diminishes
rapidly with time.
3. Use inhibitors
The use of inhibitors which will completely prevent pitting is usually economically
feasible only in closed circulating systems
4. Apply cathodic protection
An impressed current cathodic protection system will prevent pitting, or arrest pitting in
progress, and may be applied to tanks or vessels. It is not possible to cathodically protect
the inside of small diameter pipelines.
5104.05 Literature/References
ASM (Ed.): "Metals Handbook", Vol. 13 "Corrosion"
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
5104.06 List of Figures
Figure No. Figure Title (Overhead)
5104.00.01 Optional Measures to Prevent Corrosion
5104.01.01 Effects of Alloying Elements on Corrosion Resistance of Aluminium
5104.01.02 Behaviour of Different Alloys in Acids and Alkalines
5104.02.01 Severity of Galvanic Corrosion in Various Atmopheric Environments
5104.02.02 Example of the Effect of Anode to Cathode Area on Corrosion of Bi-Metal
Joints
5104.02.03 Prevention of Contact Corrosion by Electrical Insulation
5104.04.01 Prevention of Corrosion Through Cathodic Protection by Impressed DC Current
5104.04.02 Prevention of Corrosion Through Cathodic Protection By Sacrificial Anodes
5104.04.03 Prevention of Corrosion of Al-Mn Core Material Through Sacrificial Cladding
with Al-Zn Alloy
TALAT 5104 14