Corrosion is the unintentional destruction of a solid material by chemical or electrochemical reactions with its environment. There are various types of corrosion including uniform corrosion, pitting corrosion, crevice corrosion, and stress corrosion cracking. Methods for preventing corrosion include using corrosion inhibitors, protective coatings, cathodic protection, and considering corrosion resistance during the design process.
This document discusses corrosion, providing definitions and theories of corrosion. It describes dry corrosion theory involving direct reaction with gases like oxygen. Wet or galvanic corrosion theory involves formation of an electrochemical cell with oxidation at the anode and reduction at the cathode. The main types of corrosion discussed are uniform, pitting, intergranular, stress, crevice, and galvanic. Prevention methods covered include material selection, design considerations, environmental modification, and cathodic and anodic protection.
Corrosion is the deterioration of metals due to chemical or electrochemical reaction with their environment. It is a major problem worldwide that impacts safety, health, and the environment. There are many types of corrosion including uniform corrosion, pitting corrosion, stress corrosion, galvanic corrosion, and erosion corrosion. Corrosion can be prevented through various methods like using corrosion inhibitors, coatings like painting, and selecting corrosion resistant materials. The document discusses the causes, mechanisms, types, and prevention methods of corrosion in detail.
Corrosion is the decay of metals due to environmental factors like oxygen, moisture, and other gases. It can cause economic losses and safety issues like reduced machine lifespan and structural failures. There are two main types of corrosion - dry corrosion through direct chemical reactions and wet corrosion through electrochemical processes. Some factors that influence corrosion rates are the metal's position in the galvanic series, surface properties, environmental conditions, and purity. Common corrosion control methods include cathodic protection, protective coatings, and preventing exposure to corrosive substances.
This document discusses corrosion, which is the process of a metal reacting with its environment and deteriorating over time. It provides three main theories of corrosion: dry corrosion, wet corrosion, and electrochemical corrosion. Dry corrosion involves direct chemical reaction with gases, while wet corrosion occurs in conducting liquids and involves the formation of galvanic cells. There are different types of corrosion like uniform, pitting, stress, and galvanic corrosion. Prevention methods include material selection, design considerations, environmental control, cathodic protection, anodic protection, and coatings. Cathodic protection makes the metal a cathode to reduce corrosion, while anodic protection forms a protective oxide layer.
1655475850538_METALLURGY AND MATERIAL SCIENCE.pptxSahalSachu
Corrosion is the gradual destruction of materials by chemical or electrochemical reaction with their environment. There are many types of corrosion including crevice corrosion, atmospheric corrosion, pitting corrosion, stress corrosion cracking, hydrogen corrosion, erosion corrosion, and microbial corrosion. Selective leaching refers to the selective removal of one element from an alloy by corrosion processes. An example is dezincification of brass where zinc is selectively removed, leaving a porous copper-rich structure. Stress corrosion cracking results from the combined action of an applied tensile stress and a corrosive environment. Hydrogen corrosion is a type of corrosion caused by hydrogen that can lead to hydrogen embrittlement of metals like steel. Microbial corrosion involves microorganisms acceler
This document provides an overview of tarnish and corrosion as they relate to dentistry. It begins with definitions of tarnish as a surface discoloration and corrosion as deterioration of the actual metal. The document then covers the classification of corrosion into chemical/dry corrosion and electrochemical/wet corrosion. Examples of different types of electrochemical corrosion are provided, including galvanic, stress, and concentration cell corrosion. The document concludes with methods to protect against corrosion, such as passivation, increasing noble metal content, polishing, and avoiding dissimilar metal restorations.
This document discusses corrosion, providing definitions and theories of corrosion. It describes dry corrosion theory involving direct reaction with gases like oxygen. Wet or galvanic corrosion theory involves formation of an electrochemical cell with oxidation at the anode and reduction at the cathode. The main types of corrosion discussed are uniform, pitting, intergranular, stress, crevice, and galvanic. Prevention methods covered include material selection, design considerations, environmental modification, and cathodic and anodic protection.
Corrosion is the deterioration of metals due to chemical or electrochemical reaction with their environment. It is a major problem worldwide that impacts safety, health, and the environment. There are many types of corrosion including uniform corrosion, pitting corrosion, stress corrosion, galvanic corrosion, and erosion corrosion. Corrosion can be prevented through various methods like using corrosion inhibitors, coatings like painting, and selecting corrosion resistant materials. The document discusses the causes, mechanisms, types, and prevention methods of corrosion in detail.
Corrosion is the decay of metals due to environmental factors like oxygen, moisture, and other gases. It can cause economic losses and safety issues like reduced machine lifespan and structural failures. There are two main types of corrosion - dry corrosion through direct chemical reactions and wet corrosion through electrochemical processes. Some factors that influence corrosion rates are the metal's position in the galvanic series, surface properties, environmental conditions, and purity. Common corrosion control methods include cathodic protection, protective coatings, and preventing exposure to corrosive substances.
This document discusses corrosion, which is the process of a metal reacting with its environment and deteriorating over time. It provides three main theories of corrosion: dry corrosion, wet corrosion, and electrochemical corrosion. Dry corrosion involves direct chemical reaction with gases, while wet corrosion occurs in conducting liquids and involves the formation of galvanic cells. There are different types of corrosion like uniform, pitting, stress, and galvanic corrosion. Prevention methods include material selection, design considerations, environmental control, cathodic protection, anodic protection, and coatings. Cathodic protection makes the metal a cathode to reduce corrosion, while anodic protection forms a protective oxide layer.
1655475850538_METALLURGY AND MATERIAL SCIENCE.pptxSahalSachu
Corrosion is the gradual destruction of materials by chemical or electrochemical reaction with their environment. There are many types of corrosion including crevice corrosion, atmospheric corrosion, pitting corrosion, stress corrosion cracking, hydrogen corrosion, erosion corrosion, and microbial corrosion. Selective leaching refers to the selective removal of one element from an alloy by corrosion processes. An example is dezincification of brass where zinc is selectively removed, leaving a porous copper-rich structure. Stress corrosion cracking results from the combined action of an applied tensile stress and a corrosive environment. Hydrogen corrosion is a type of corrosion caused by hydrogen that can lead to hydrogen embrittlement of metals like steel. Microbial corrosion involves microorganisms acceler
This document provides an overview of tarnish and corrosion as they relate to dentistry. It begins with definitions of tarnish as a surface discoloration and corrosion as deterioration of the actual metal. The document then covers the classification of corrosion into chemical/dry corrosion and electrochemical/wet corrosion. Examples of different types of electrochemical corrosion are provided, including galvanic, stress, and concentration cell corrosion. The document concludes with methods to protect against corrosion, such as passivation, increasing noble metal content, polishing, and avoiding dissimilar metal restorations.
Corrosion is the degradation of a material due to a reaction with its environment. It is a slow process that involves the destruction of a material through chemical or electrochemical reactions on its surface. There are several types of corrosion that can occur depending on factors like the environment and the material. Proper selection of materials and use of protective coatings or cathodic protection techniques can help reduce corrosion of structures and extend their lifetimes.
Corrosion is the deterioration of materials by chemical, electrochemical or metallurgical interaction with their environment. It involves the oxidation and reduction of metals and can have serious consequences like structural failure, reduced mechanical strength, and economic losses. The rate and type of corrosion depends on factors like the metal composition, environment, presence of other ions, stresses, and temperature. Common types of corrosion include uniform corrosion, pitting corrosion, galvanic corrosion, stress corrosion, and corrosion fatigue. Corrosion can be tested using methods like salt spray testing and immersion in corrosive media. Prevention focuses on removing one of the three requirements for corrosion - the metal, oxygen, or water/electrolyte.
Corrosion Metallurgy presents various forms of corrosion including uniform corrosion, pitting corrosion, crevice corrosion, galvanic corrosion, selective leaching, erosion corrosion, stress corrosion cracking, and intergranular corrosion. Metallurgical factors that influence corrosion rates include material properties like composition and crystal structure, microstructure features such as phases and grain boundaries, the degree and type of mechanical deformation, heat treatments applied, and the formation of passive surface layers. Understanding how these metallurgical factors impact corrosion is important for corrosion prevention and mitigation.
This document discusses metal corrosion and its prevention. It defines corrosion as the destruction or deterioration of solid metallic materials due to chemical or electrochemical attack from their environment. Corrosion is a major problem worldwide that impacts safety, health, and the environment. The document describes various types of corrosion including uniform corrosion, pitting corrosion, stress corrosion cracking, galvanic corrosion, and erosion corrosion. It also discusses factors that influence corrosion and various methods to prevent corrosion, such as using corrosion inhibitors, cathodic protection, coatings, and selecting corrosion-resistant materials.
This document discusses corrosion of dental materials. It defines corrosion as an electrochemical process that causes metal deterioration and failure. Corrosion can cause pulpal pain, toxic reactions, and metallic taste. It occurs via chemical or electrochemical mechanisms. Electrochemical corrosion requires an electrolyte and occurs via galvanic, heterogeneous surface composition, stress, or concentration cell corrosion when different areas of a restoration have different electrolyte compositions. Protection against corrosion can come from using passive metals like chromium, keeping surfaces polished, or using protective coatings.
This document discusses various forms of corrosion that can occur in metals. It begins by defining corrosion and explaining the factors that influence it. It then describes several specific types of corrosion: general/uniform corrosion, galvanic corrosion, crevice corrosion, pitting corrosion, intergranular corrosion, dealloying, erosion corrosion, stress corrosion, hydrogen damage including hydrogen blistering and hydrogen embrittlement. For each type of corrosion, the document discusses the mechanism and provides methods for prevention.
There are 10 main types of corrosion described in the document:
1. Uniform corrosion which causes general dulling and roughening of surfaces.
2. Galvanic corrosion which occurs when two dissimilar metals contact in an electrolyte.
3. Stress corrosion which occurs in fabricated metals under mechanical stress.
4. The document also describes ways to prevent each type of corrosion, including using protective coatings, corrosion inhibitors, sacrificial anodes, and considering material selection and design modifications.
This document discusses various types and theories of corrosion. It begins by introducing corrosion as the chemical reaction between a metal and its environment that causes the metal to deteriorate. It then describes three main theories of corrosion: the acid theory, dry/chemical theory, and galvanic/electrochemical theory. The rest of the document details eight specific types of corrosion including uniform, pitting, intergranular, exfoliation, stress, crevice, galvanic, and erosion corrosion. It provides examples and explanations for each type.
Mechanical stresses can increase corrosion rates by creating sites of localized corrosion. Stress corrosion cracking occurs when three factors are present: a susceptible alloy, a corrosive environment, and tensile stress. It can cause sudden failures. Cold work increases corrosion by segregating impurities. Heat treatment can reduce this effect. Hydrogen embrittlement and corrosion fatigue are additional failure modes involving the combined effects of corrosion and stress. Proper material selection, coatings, inhibitors, and heat treatments can mitigate these issues.
This document discusses different types of corrosion that commonly occur in metals, their features, and preventive measures. It outlines 9 main types of corrosion - atmospheric, erosion, selective, uniform, pitting, fretting, stress, intergranular, and corrosion fatigue. It then explains features and examples of each type. The document concludes by covering various prevention methods like material selection, design considerations, use of inhibitors, cathodic protection, galvanization, and protective coatings.
Types of corrosion and Prevention of corrosionHemal Machhi
This document discusses different types of corrosion that commonly occur in metals, their features, and preventive measures. It outlines 9 main types of corrosion - atmospheric, erosion, selective, uniform, pitting, fretting, stress, intergranular, and corrosion fatigue. It then explains features and examples of each type. The document concludes by covering various prevention methods like material selection, design considerations, use of inhibitors, cathodic protection, galvanization, and protective coatings.
Erosion corrosion occurs when the rate of material deterioration increases due to the combined effects of corrosion and mechanical wear from fluid flow. It can occur in pipes, valves, pumps and other equipment exposed to flowing liquids or gases. The mechanism involves turbulent flow damaging protective surface films and exposing the bare metal to chemical attack. Common signs are grooves, holes and valleys in the direction of flow. Prevention methods include design modifications to reduce turbulence, removing abrasive particles from the fluid, protective coatings, cathodic protection, and using more corrosion resistant materials.
This seminar explains the basics of tarnish and corrosion on dental restorations.
All metals undergo a little bit of degradation and hence it is essential for prosthodontics and endodontic restoration.
Corrosion is the gradual destruction of materials due to chemical or electrochemical reaction with their environment. Corrosion engineering studies corrosion mechanisms and works to prevent or control corrosion economically and safely. There are two main types of corrosion - general attack corrosion which uniformly destroys metal over time, and localized corrosion which targets specific areas. Localized corrosion includes pitting, crevice corrosion, filiform corrosion, galvanic corrosion, and others. Proper material selection and protective coatings can help prevent corrosion in pharmaceutical facilities and equipment.
Corrosion is an electrochemical process where a metal oxidizes and dissolves into its environment. There are several types of corrosion including uniform corrosion, galvanic corrosion, pitting corrosion, and crevice corrosion. Uniform corrosion proceeds uniformly over the entire metal surface. Galvanic corrosion occurs when two dissimilar metals are electrically coupled in a corrosive electrolyte. Pitting and crevice corrosion are localized forms of attack that can cause perforation. Cathodic protection is a technique to control the corrosion of a metal by making it the cathode of an electrochemical cell.
This document discusses various types of corrosion and methods for corrosion prevention. It describes 12 types of localized corrosion including pitting, crevice, stress, fretting, erosion, cavitation, galvanic, oxygen concentration cell, corrosion fatigue, impingement attack, hydrogen embrittlement, and two types of structural corrosion - graphite and dezincification. The document also mentions biological corrosion caused by microorganisms. Finally, it states that corrosion can be prevented by proper material selection, coating application, cathode protection, corrosion inhibitors, and design modifications.
This document discusses different types of corrosion, including uniform corrosion, galvanic corrosion, crevice corrosion, and pitting corrosion. Uniform corrosion affects the entire exposed metal surface at a generally predictable and low rate. Galvanic corrosion occurs when two dissimilar metals are electrically coupled in an electrolyte. Crevice corrosion happens in cracks or gaps where oxygen is depleted. Pitting corrosion produces small, deep pits and is very destructive despite only causing small weight loss. The document explains the mechanisms and factors that influence each corrosion type and provides strategies for prevention.
Corrosion Chemistry : Its Causes and RemedyArijitDhali
This Conceptual Power Point project consists of a grieve description about the science of Corrosion, perfect for covering whole topic for short period of time. The project consists of basic knowledge regarding corrosion, its type of causes that is dry and wet corrosion. It also summarizes about different types of differential corrosion and its remedies. Its allover a good conceptual ppt for students of chemistry in their prelims. It's good for the ones achieving for engineering degrees.
The document discusses corrosion of metals and its prevention. It defines corrosion as the deterioration of metals due to reaction with the environment. Corrosion reactions are electrochemical in nature involving electron transfer. The standard electrode potential and electrochemical series are used to predict which metal will corrode in a galvanic cell based on their position in the series. The different types of corrosion such as uniform, galvanic, crevice and pitting corrosion are described. Methods to prevent corrosion include proper material selection, cathodic protection, altering the environment, and applying protective coatings.
Corrosion is the degradation of a material due to a reaction with its environment. It is a slow process that involves the destruction of a material through chemical or electrochemical reactions on its surface. There are several types of corrosion that can occur depending on factors like the environment and the material. Proper selection of materials and use of protective coatings or cathodic protection techniques can help reduce corrosion of structures and extend their lifetimes.
Corrosion is the deterioration of materials by chemical, electrochemical or metallurgical interaction with their environment. It involves the oxidation and reduction of metals and can have serious consequences like structural failure, reduced mechanical strength, and economic losses. The rate and type of corrosion depends on factors like the metal composition, environment, presence of other ions, stresses, and temperature. Common types of corrosion include uniform corrosion, pitting corrosion, galvanic corrosion, stress corrosion, and corrosion fatigue. Corrosion can be tested using methods like salt spray testing and immersion in corrosive media. Prevention focuses on removing one of the three requirements for corrosion - the metal, oxygen, or water/electrolyte.
Corrosion Metallurgy presents various forms of corrosion including uniform corrosion, pitting corrosion, crevice corrosion, galvanic corrosion, selective leaching, erosion corrosion, stress corrosion cracking, and intergranular corrosion. Metallurgical factors that influence corrosion rates include material properties like composition and crystal structure, microstructure features such as phases and grain boundaries, the degree and type of mechanical deformation, heat treatments applied, and the formation of passive surface layers. Understanding how these metallurgical factors impact corrosion is important for corrosion prevention and mitigation.
This document discusses metal corrosion and its prevention. It defines corrosion as the destruction or deterioration of solid metallic materials due to chemical or electrochemical attack from their environment. Corrosion is a major problem worldwide that impacts safety, health, and the environment. The document describes various types of corrosion including uniform corrosion, pitting corrosion, stress corrosion cracking, galvanic corrosion, and erosion corrosion. It also discusses factors that influence corrosion and various methods to prevent corrosion, such as using corrosion inhibitors, cathodic protection, coatings, and selecting corrosion-resistant materials.
This document discusses corrosion of dental materials. It defines corrosion as an electrochemical process that causes metal deterioration and failure. Corrosion can cause pulpal pain, toxic reactions, and metallic taste. It occurs via chemical or electrochemical mechanisms. Electrochemical corrosion requires an electrolyte and occurs via galvanic, heterogeneous surface composition, stress, or concentration cell corrosion when different areas of a restoration have different electrolyte compositions. Protection against corrosion can come from using passive metals like chromium, keeping surfaces polished, or using protective coatings.
This document discusses various forms of corrosion that can occur in metals. It begins by defining corrosion and explaining the factors that influence it. It then describes several specific types of corrosion: general/uniform corrosion, galvanic corrosion, crevice corrosion, pitting corrosion, intergranular corrosion, dealloying, erosion corrosion, stress corrosion, hydrogen damage including hydrogen blistering and hydrogen embrittlement. For each type of corrosion, the document discusses the mechanism and provides methods for prevention.
There are 10 main types of corrosion described in the document:
1. Uniform corrosion which causes general dulling and roughening of surfaces.
2. Galvanic corrosion which occurs when two dissimilar metals contact in an electrolyte.
3. Stress corrosion which occurs in fabricated metals under mechanical stress.
4. The document also describes ways to prevent each type of corrosion, including using protective coatings, corrosion inhibitors, sacrificial anodes, and considering material selection and design modifications.
This document discusses various types and theories of corrosion. It begins by introducing corrosion as the chemical reaction between a metal and its environment that causes the metal to deteriorate. It then describes three main theories of corrosion: the acid theory, dry/chemical theory, and galvanic/electrochemical theory. The rest of the document details eight specific types of corrosion including uniform, pitting, intergranular, exfoliation, stress, crevice, galvanic, and erosion corrosion. It provides examples and explanations for each type.
Mechanical stresses can increase corrosion rates by creating sites of localized corrosion. Stress corrosion cracking occurs when three factors are present: a susceptible alloy, a corrosive environment, and tensile stress. It can cause sudden failures. Cold work increases corrosion by segregating impurities. Heat treatment can reduce this effect. Hydrogen embrittlement and corrosion fatigue are additional failure modes involving the combined effects of corrosion and stress. Proper material selection, coatings, inhibitors, and heat treatments can mitigate these issues.
This document discusses different types of corrosion that commonly occur in metals, their features, and preventive measures. It outlines 9 main types of corrosion - atmospheric, erosion, selective, uniform, pitting, fretting, stress, intergranular, and corrosion fatigue. It then explains features and examples of each type. The document concludes by covering various prevention methods like material selection, design considerations, use of inhibitors, cathodic protection, galvanization, and protective coatings.
Types of corrosion and Prevention of corrosionHemal Machhi
This document discusses different types of corrosion that commonly occur in metals, their features, and preventive measures. It outlines 9 main types of corrosion - atmospheric, erosion, selective, uniform, pitting, fretting, stress, intergranular, and corrosion fatigue. It then explains features and examples of each type. The document concludes by covering various prevention methods like material selection, design considerations, use of inhibitors, cathodic protection, galvanization, and protective coatings.
Erosion corrosion occurs when the rate of material deterioration increases due to the combined effects of corrosion and mechanical wear from fluid flow. It can occur in pipes, valves, pumps and other equipment exposed to flowing liquids or gases. The mechanism involves turbulent flow damaging protective surface films and exposing the bare metal to chemical attack. Common signs are grooves, holes and valleys in the direction of flow. Prevention methods include design modifications to reduce turbulence, removing abrasive particles from the fluid, protective coatings, cathodic protection, and using more corrosion resistant materials.
This seminar explains the basics of tarnish and corrosion on dental restorations.
All metals undergo a little bit of degradation and hence it is essential for prosthodontics and endodontic restoration.
Corrosion is the gradual destruction of materials due to chemical or electrochemical reaction with their environment. Corrosion engineering studies corrosion mechanisms and works to prevent or control corrosion economically and safely. There are two main types of corrosion - general attack corrosion which uniformly destroys metal over time, and localized corrosion which targets specific areas. Localized corrosion includes pitting, crevice corrosion, filiform corrosion, galvanic corrosion, and others. Proper material selection and protective coatings can help prevent corrosion in pharmaceutical facilities and equipment.
Corrosion is an electrochemical process where a metal oxidizes and dissolves into its environment. There are several types of corrosion including uniform corrosion, galvanic corrosion, pitting corrosion, and crevice corrosion. Uniform corrosion proceeds uniformly over the entire metal surface. Galvanic corrosion occurs when two dissimilar metals are electrically coupled in a corrosive electrolyte. Pitting and crevice corrosion are localized forms of attack that can cause perforation. Cathodic protection is a technique to control the corrosion of a metal by making it the cathode of an electrochemical cell.
This document discusses various types of corrosion and methods for corrosion prevention. It describes 12 types of localized corrosion including pitting, crevice, stress, fretting, erosion, cavitation, galvanic, oxygen concentration cell, corrosion fatigue, impingement attack, hydrogen embrittlement, and two types of structural corrosion - graphite and dezincification. The document also mentions biological corrosion caused by microorganisms. Finally, it states that corrosion can be prevented by proper material selection, coating application, cathode protection, corrosion inhibitors, and design modifications.
This document discusses different types of corrosion, including uniform corrosion, galvanic corrosion, crevice corrosion, and pitting corrosion. Uniform corrosion affects the entire exposed metal surface at a generally predictable and low rate. Galvanic corrosion occurs when two dissimilar metals are electrically coupled in an electrolyte. Crevice corrosion happens in cracks or gaps where oxygen is depleted. Pitting corrosion produces small, deep pits and is very destructive despite only causing small weight loss. The document explains the mechanisms and factors that influence each corrosion type and provides strategies for prevention.
Corrosion Chemistry : Its Causes and RemedyArijitDhali
This Conceptual Power Point project consists of a grieve description about the science of Corrosion, perfect for covering whole topic for short period of time. The project consists of basic knowledge regarding corrosion, its type of causes that is dry and wet corrosion. It also summarizes about different types of differential corrosion and its remedies. Its allover a good conceptual ppt for students of chemistry in their prelims. It's good for the ones achieving for engineering degrees.
The document discusses corrosion of metals and its prevention. It defines corrosion as the deterioration of metals due to reaction with the environment. Corrosion reactions are electrochemical in nature involving electron transfer. The standard electrode potential and electrochemical series are used to predict which metal will corrode in a galvanic cell based on their position in the series. The different types of corrosion such as uniform, galvanic, crevice and pitting corrosion are described. Methods to prevent corrosion include proper material selection, cathodic protection, altering the environment, and applying protective coatings.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Travis Hills of MN is Making Clean Water Accessible to All Through High Flux ...Travis Hills MN
By harnessing the power of High Flux Vacuum Membrane Distillation, Travis Hills from MN envisions a future where clean and safe drinking water is accessible to all, regardless of geographical location or economic status.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
2. Objective
• What is corrosion
• Classification of corrosion
• Mechanism of corrosion
• Types of corrosion
• Corrosion prevention methods
3. Introduction
• Corrosion is defined as unintentional destruction of a solid
body by chemical or electrochemical reactions starting from
the surface.
• Non-Metals corrode by chemical reactions & metals mostly by
electrochemical reactions.
• Metals are at high energy levels & hence there is natural
tendency to go to the low energy state i.e. they try to form
oxides, hydroxides, carbonates, sulphides etc. depending on
the type of environment to which they are exposed.
4. Chemical vs. Electrochemical Reactions
• Chemical reactions are those in which elements are
added or removed from a chemical species
• Electrochemical reactions are chemical reactions in
which not only elements may be added or removed from
a chemical species but at least one of the species
undergoes a change in the number of valance electron
• Corrosion processes are electrochemical in nature
6. Dry corrosion
• Dry corrosion occurs when the metals are exposed to
gaseous environment
• The extent of corrosion & protective values depends
on the following factors
1. Chemical affinity between the environment & the metal.
2. Protective value of film.
3. Nature of film formed.
4. Adhesion between the film & the metal surface.
5. For non ferrous film, the extent of corrosion depends on the
electronic & ionic conductivities of the film.
7. Pilling & Bedworth Rule
• This rules gives the idea about the nature of the film formed
i.e. whether the film is porous or nonporous.
Volume of oxide
• Pilling & Bedworth Ratio =
Volume of equivalent amount
of metal consumed during oxidation
= Md/mD
8. Formation & Growth Of Film
• The formation & growth of films occur by three successive
stages
1. Adsorption
2. Chemisorptions
3. Growth of film
3.1 Growth of non porous film
3.2 Growth of porous film
9. Wet corrosion
• Wet corrosion occur when a metal or an alloy comes in contact with
an aqueous solution of salt, acid or alkali by an electrochemical type
of reaction.
• When a metal is immersed in an aqueous electrolyte,it dissolve /
dissociate into metal ion + electron.
• This tendency of metal is called as electrolytic pressure or solution
pressure (p)
• The dissolved ion from the solution tend to deposit on the immersed
metal surface& oppose the solution pressure of metal. This tendency
is called as osmotic pressure of metal ion (p)
• When these forces become equal, equilibrium is reached and under
this condition, a definite number of electrons accumulate on the
metal surface & a definite potential will be developed on the metal
piece.
10.
11. What is the voltage difference
between Zinc (Zn) and Copper
(Cu)?
An. 0.67v
What is more noble than
Stainless Steel (Passive)?
An. Graphite
12. Mechanism Of Wet Corrosion
• The reaction at anode is always oxidation reaction & is
associated with the dissolution of metal i.e.
Metal Metal ions + electron
• The reaction at cathode is always a reduction reaction with no
corrosion of cathode & varies depending on the nature of
electrolyte in contact
1. Hydrogen evolution :
2. Oxygen absorption :
13. 1.Hydrogen evolution :
• The hydrogen evolution occurs at the cathode in concentrated
acidic environment (pH < 4) usually iron surface is covered
with oxide at least at few points or it may difference in
hydrogen over potential from point to point
• Due to this some areas act as cathode with respect to other
areas which behaves as anode of the cell & galvanic corrosion
occurs.
• At the anode : Fe Fe++ + 2e
• At the cathode : 2H+ + 2e H2
• it is clear from the reaction that hydrogen evolution type of
corrosion occurs by simple displacement of hydrogen ion from
acidic solution by metal ion.
continue …..
14.
15. 2. Oxygen Absorption
• Oxygen absorption mechanism of corrosion occurs in mild acidic
or alkaline environment (pH > 4)
• The above process for the rusting of iron taking an electrolyte of
aqueous solution of sodium chloride.
• The area which are not covered with the oxide become anodic
with respect to the areas covered with the oxide which become
cathodic & corrosion occurs by the following reactions :
• Reaction at anode :Fe Fe++ + 2e & Fe++ + 2Cl- FeCl2
• Reaction at cathode : 4e + O2 + 2H2O 4OH-
• OH- + Na+ NaOH
• Both the anodic product FeCl2 & cathodic product NaOH are
soluble in water & diffuse towards each other.
continue….
16. • When both meet ferrous hydroxide is formed. In the presence
sufficient dissolved oxygen, ferrous hydroxide is further
oxidized to ferric hydroxide which has very little solubility in
water & precipitate out as yellow rust.
• It is clear that there is no concentration polarization at both
the electrode.
17.
18. Types Of Corrosion
• General corrosion
• Pitting corrosion
• Crevice corrosion
• Intergranular corrosion
• Stress corrosion cracking
• Erosion – corrosion
• Cavitation corrosion
• Corrosion fatigue
• Hydrogen blistering
• High temperature corrosion
19. • General / Uniform Corrosion
• Corrosion proceeds at the same rate throughout the area
exposed to the environment & there is no clearly defined anode
& cathode areas.
• the extent of corrosion can be expressed by loss in weight per
unit area or by average penetration depth
20. Pitting Corrosion
• Pitting corrosion is a localized accelerated corrosion resulting
in the formation of cavities around which the metal is
relatively unattacked.
21. • Small anodic area & large cathodic areas results in high anodic
current density leading to rapid corrosion of small anodic
areas forming pit or pinholes
• This results in rapid perforation of metal sharply reducing the
mechanical properties of of the component.
• Pitting has more effect on fatigue strength
• Pitting corrosion can occur under following situations:
1. Due to break in the protective coating
2. Due to destruction of passive layer at few points under
certain environmental conditions.
3. Differential aeration corrosion may lead to pitting corrosion
continue…
22. • Crevice corrosion, corrosion take place in crevices bcz
solutions retained at this place and takes longer time
to dry out. When this occurs, the severity of attack is
more severe at crevices. Crevices are formed bcz of
the metal contact with another piece of the same or
other metal or with a nonmetallic material. Corrosion
in crevice is due to deficiency of O2, Acidity changes,
23. • Crevice Corrosion
– narrow crevice filled with ionized solution
– Oxygen-rich on the outside, oxygen-poor on the
inside
– metals oxidize with salt anions FeCl2 and pH rises
in cathodic zone
– H+ may destroy passivity
24. Intergranular Corrosion
• This types of corrosion occurs at the grain boundaries or at
the region adjacent to the grain boundaries due to
precipitation of some phase at the grain boundaries
25. • The precipitate phase makes the material sensitive to
corrosion
• The grain boundary phase or the region adjacent to grain
boundary become anodic & get preferentially corroded
• This type of corrosion can occur even without the
precipitation of phase at the grain boundaries, this is because
the grain boundary regions being high energy region will get
preferentially corroded due to their low electrode potential
compared to the electrode potential of grain
• E.g. Corrosion of Austenitic stainless steels due to
precipitation of complex chromium carbide along grain
boundaries.
• Weld decay.
27. • This type of corrosion occurs due to presence of stresses in the
material
• The stresses area become anodic with respect to the other
areas & get corroded by forming stress cell.
• It has been observed that if the stresses are tensile, it leads to
cracking of the material in due course of time when exposed to
certain environmental conditions & hence the phenomenon is
known as SCC.
• The static tensile stress present in the material may be residual
(internal) or applied (external).
• Internal stresses are developed due to cold working processes,
or due to rapid cooling, poor design, precipitation of second
phase.
• External stresses are produced due to application of external
load on the components.
28. • Erosion – corrosion type of corrosion occurs by the
simultaneous effect of corrosion & erosion produced by the
turbulent flow of electrolyte, & also by the rubbing action of
solid particle over a metal surface.
• This type of corrosion can occur in any metal & alloy.
• In many cases, it has been observed that the damage to the
metal is due to the breaking of protective coating of corrosion
product & coating is not get repaired due to turbulence flow
of electrolyte.
• This type of corrosion is usually occurs in the regions where
the flow of electrolyte is disturbed e.g. bend in pipes,
condenser tube, valve seat in in water fitting etc.
29. Corrosion prevention Methods
Inhibitors
• Inhibitors is a substance which effectively decreases the
corrosion rate of a metal when added in small amount to the
corrosive environment.
• These substances control the anodic or cathodic reactions
reducing the corrosion of metals.
1. Anodic Inhibitors
2. Cathodic Inhibitors
30. Anodic Inhibitors
• Anodic inhibitors when added to the electrolyte combine with
the newly form metal ions at the anode & form a precipitate.
• This precipitate deposit on the anode surface forming a
protective layer which stops or reduce the corrosion
• Thus the local anode areas get polarized i.e. increase In
potential occurs at these areas.
• Anodic inhibitors work effectively when they are added in
sufficient amount.
31. Cathodic Inhibitors
• Cathodic inhibitors reduce the corrosion by stopping the
cathodic reaction
• In acidic electrolyte, cathodic reactions is of hydrogen
evolution type
• In such case, corrosion can be reduced by reducing the
diffusion of hydrogen ion to the cathode or by increasing the
over potential of hydrogen.
• The diffusion of hydrogen ion is reduced by using certain
organic compounds.
• hydrogen over potential is increased by adding salts of As, Sb
& Bi.
32. Protective Coatings / Wrapping
• Provide barrier between metal and environment.
• Coatings may act as sacrificial anode or release substance
that inhibit corrosive attack on substrate.
• Metal coatings :
– Noble – silver, copper, nickel, Cr, Sn, Pb on steel.
Should be free of pores/discontinuity coz creates
small anode-large cathode leading to rapid attack
at the damaged areas.
– Sacrificial – Zn, Al, Cd on steel. Exposed substrate
will be cathodic & will be protected.
– Application – hot dipping, flame spraying, cladding,
electroplating, vapor deposition, etc.
33. • Surface modification – to structure or composition by use
of directed energy or particle beams. E.g ion implantation
and laser processing.
• Inorganic coating : cement coatings, glass coatings, ceramic
coatings, chemical conversion coatings.
• Chemical conversion – anodizing, phosphatizing, oxide
coating, chromate.
• Organic coating : paints, lacquers, varnishes. Coating liquid
generally consists of solvent, resin and pigment. The resin
provides chemical and corrosion resistance, and pigments
may also have corrosion inhibition functions.
34. • Surface modification – to structure or composition by use
of directed energy or particle beams. E.g ion implantation
and laser processing.
• Inorganic coating : cement coatings, glass coatings, ceramic
coatings, chemical conversion coatings.
• Chemical conversion – anodizing, phosphatizing, oxide
coating, chromate.
• Organic coating : paints, lacquers, varnishes. Coating liquid
generally consists of solvent, resin and pigment. The resin
provides chemical and corrosion resistance, and pigments
may also have corrosion inhibition functions.
35. • Paints, pigments are also widely used for the protection of
metallic component.
3. Anodized Coating (Chemical Conversion Coating)
• In atmospheric conditions Al, Al alloys, Ti, Ti alloys form a thin
film of oxide on their surfaces.
• This thin film of oxide provides a good resistance to further
corrosion of the above materials.
• However, under the normal atmosphere conditions the
thickness of oxide layer is very small & does not protect the
metal from corrosion under severe condition of exposure.
• to make this materials highly corrosion resistant, the naturally
existing film of oxide is increased in thickness by electrrolysis.
36. • Paints, pigments are also widely used for the protection of
metallic component.
3. Anodized Coating (Chemical Conversion Coating)
• In atmospheric conditions Al, Al alloys, Ti, Ti alloys form a thin
film of oxide on their surfaces.
• This thin film of oxide provides a good resistance to further
corrosion of the above materials.
• However, under the normal atmosphere conditions the
thickness of oxide layer is very small & does not protect the
metal from corrosion under severe condition of exposure.
• to make this materials highly corrosion resistant, the naturally
existing film of oxide is increased in thickness by electrrolysis.
37. • The electrolysis process used for increasing thickness of oxide
film is called anodizing.
• The metal is not coated by any other material as is done in the
previous method, but the surface of metal is converted into
oxide & hence they can called as chemical conversion coating.
38. Anodic Protection (Cathodic coating)
• Here the metal get protect anodic by the application of
coating of cathodic material.
• Coating of Ni & Cr on Fe & steel, Coating of Au, Ag on brasses
or bronzes.
• When the coating is dense, non porous & continuous, the
electrolyte does not come in contact with the component &
hence the component does not corrode.
39. Cathodic protection (Anodic Coating)
• Here the metal get protect cathode by the application of
coating of anodic material.
• Coating of Zn & Cd on iron & steel
• When the coating is dense, nonporous & continuous, the
electrolyte does not come in contact with the component &
hence the component does not corrode.
• The coating metal completely separate the electrolyte from
metal.
• Such coating completely prevent the component from
corrosion even in the presence of discontinuous or breaks.
42. • Avoid sharp corners – paint tends to be thinner at sharp
corners and often starts to fail.
• Provide for easy drainage (esp tanks) – avoid remaining
liquids collect at bottom. E.g steel is resistant against
concentrated sulfuric acid. But if remaining liquid is
exposed to air, acid tend to absorb moisture, resulting in
dilution and rapid attack occurs.
• Avoid hot spots during heat transfer operations – localized
heating and high corrosion rates. Hot spots also tend to
produce stresses – SCC failures.
• Design to exclude air – except for active-passive metals and
alloys coz they require O2 for protective films.
• Most general rule : AVOID HETEROGENEITY!!!
44. -
Organic compounds with an
electronegative atom or an
electron-withdrawing group
bonded to a sp3 carbon
undergo substitution or
elimination reactions
Halide ions are good leaving
groups. Substitution reaction
on these compounds are easy
and are used to get a wide
variety of compounds
alkyl fluoride alkyl chloride alkyl bromide alkyl iodide
45. Substitution Reaction with Halides
If concentration of (1) is
doubled, the rate of the
reaction is doubled.
bromomethane
(1)
(2)
If concentration of (2) is
doubled, the rate of the
reaction is doubled.
If concentration of (1) and
(2) is doubled, the rate of
the reaction quadruples.
methanol
46. Substitution Reaction with Halides
bromomethane
(1)
(2)
methanol
Rate law:
rate = k [bromoethane][OH-]
this reaction is an example of a SN2 reaction.
S stands for substitution
N stands for nucleophilic
2 stands for bimolecular
47. Mechanism of SN2 Reactions
The rate of reaction depends on the
concentrations of both reactants.
When the hydrogens of bromomethane
are replaced with methyl groups the
reaction rate slow down.
The reaction of an alkyl halide in which
the halogen is bonded to an asymetric
center leads to the formation of only
one stereoisomer
Alkyl halide Relative rate
1200
40
1
≈ 0
48. Mechanism of SN2 Reactions
Hughes and Ingold proposed the following mechanism:
Transition state
Increasing the concentration of either of the
reactant makes their collision more probable.
49. Mechanism of SN2 Reactions
activation
energy: DG1
activation
energy: DG2
Steric effect
Inversion of configuration
(R)-2-bromobutane (S)-2-butanol
Energy
reaction coordinate reaction coordinate
50. Factor Affecting SN2 Reactions
relative rates of reaction pKa HX
HO
- + RCH2I RCH2OH + I
- 30 000 -10
HO
- + RCH2Br RCH2OH + Br
- 10 000 -9
HO
- + RCH2Cl RCH2OH + Cl
- 200 -7
HO
- + RCH2F RCH2OH + F
- 1 3.2
The leaving group
The nucleophile
In general, for halogen substitution the
strongest the base the better the
nucleophile.
pKa Nuclephilicity
51. SN2 Reactions With Alkyl Halides
an alcohol
a thiol
an ether
a thioether
an amine
an alkyne
a nitrile
52. Substitution Reactions With Halides
If concentration of (1) is
doubled, the rate of the
reaction is doubled.
If concentration of (2) is
doubled, the rate of the
reaction is not doubled.
Rate law:
rate = k [1-bromo-1,1-dimethylethane]
this reaction is an example of a SN1
reaction.
S stands for substitution
N stands for nucleophilic
1 stands for unimolecular
1-bromo-1,1-dimethylethane 1,1-dimethylethanol
53. Mechanism of SN1 Reactions
The rate of reaction depends on the
concentrations of the alkyl halide only.
When the methyl groups of 1-bromo-
1,1-dimethylethane are replaced with
hydrogens the reaction rate slow down.
The reaction of an alkyl halide in which
the halogen is bonded to an asymetric
center leads to the formation of two
stereoisomers
Alkyl halide Relative rate
≈ 0 *
≈ 0 *
12
1 200 000
* a small rate is actually observed as a result of a SN2
54. Mechanism of SN1 Reactions
C-Br bond breaks
nucleophile attacks the
carbocation
Proton dissociation
slow
fast
55. Mechanism of SN1 Reactions
Same configuration
as the alkyl halide
Inverted
configuration relative
the alkyl halide
56. Factor Affecting SN1 reaction
Two factors affect the rate of a SN1 reaction:
• The ease with which the leaving group dissociate from the carbon
• The stability of the carbocation
The more the substituted the
carbocation is, the more
stable it is and therefore the
easier it is to form.
As in the case of SN2, the
weaker base is the leaving
group, the less tightly it is
bonded to the carbon and the
easier it is to break the bond
The reactivity of the
nucleophile has no effect on
the rate of a SN1 reaction
57. Comparison SN1 – SN2
SN1 SN2
A two-step mechanism A one-step mechanism
A unimolecular rate-determining step A bimolecular rate-determining step
Products have both retained and inverted
configuration relative to the reactant
Product has inverted configuration
relative to the reactant
Reactivity order:
3o > 2o > 1o > methyl
Reactivity order:
methyl > 1o > 2o > 3o
59. The E2 Reaction
A proton is
removed
Br- is eliminated
The mechanism shows that an E2
reaction is a one-step reaction
60. The E1 Reaction
The alkyl halide
dissociate, forming a
carbocation
The base
removes a proton
The mechanism shows that an E1
reaction is a two-step reaction
61. Products of Elimination Reaction
2-bromobutane
2-butene
1-butene
80%
20%
The most stable alkene is the
major product of the reaction
for both E1 and E2 reaction
The greater the number of
alkyl substituent the more
stable is the alkene
For both E1 and E2 reactions, tertiary alkyl halides
are the most reactive and primary alkyl halides
are the least reactive
30% 50%
62. Competition Between
SN2/E2 and SN1/E1
rate = k1[alkyl halide] + k2[alkyl halide][nucleo.] + k3[alkyl halide] + k2[alkyl halide][base]
SN1 SN2 E1 E2
• SN2 and E2 are favoured by a high concentration of a good
nucleophile/strong base
• SN1 and E1 are favoured by a poor nucleophile/weak base, because a
poor nucleophile/weak base disfavours SN2 and E2 reactions
63. Competition Between
Substitution and Elimination
• SN2/E2 conditions: In a SN2 reaction: 1o > 2o > 3o
In a E2 reaction: 3o > 2o > 1o
90% 10%
25% 75%
100%
64. Competition Between
Substitution and Elimination
• SN1/E1 conditions:
All alkyl halides that react under SN1/E1 conditions will give
both substitution and elimination products (≈50%/50%)