Lecture 2022-10-28.pdf
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This document discusses corrosion engineering and corrosion testing. It begins with introductions to corrosion science and corrosion engineering. It then discusses the responsibilities of corrosion engineers, including ensuring safety and minimizing economic losses from corrosion. Direct economic losses include replacing corroded structures, while indirect losses include shutdowns and loss of efficiency. The document also summarizes various examples of corrosion, classifies corrosion into wet and dry types, and explains corrosion as an electrochemical reaction. It describes equipment used for corrosion testing like electrochemical workstations and defines key terms like potential and current. Finally, it discusses open circuit potential graphs used in corrosion testing.
Lecture 2022-10-28.pdf
- 1. MM- 539 Corrosion Engineering Dr. M. Ali Siddiqui PhD, Materials Science and Engineering Institute of Metal Research – Chinese Academy of Sciences “Electrochemical Corrosion of Biomaterials” Assistant Professor Metallurgical Engineering Department Materials Engineering Department
- 2. • What is Corrosion Science? • Fundamental Knowledge of ….. • What is Corrosion Engineering ? • Applied Knowledge of ….. Dr. MAS - NED UET Karachi - Pakistan 2
- 3. Dr. MAS - NED UET Karachi - Pakistan 3 Your responsibility as Corrosion Engineer?
- 4. • Safety and economics are generally considered deleterious effect of corrosion. • Corrosion can demolish the safety of operating equipment by causing failure (with catastrophic consequences), • for example, pressure vessels, boilers, metallic containers for toxic chemicals, turbine blades and rotors, bridges, airplane components, and automotive steering mechanisms. Dr. MAS - NED UET Karachi - Pakistan 4
- 5. Economic losses are divided into • (1) Direct losses and (2) Indirect losses. • Direct loses includes the costs of replacing corroded structures and machinery or their components. • rebuilding/upgrading corroded equipment requires further investment of all these resource metal, energy, water, and human Dr. MAS - NED UET Karachi - Pakistan 5
- 6. • Indirect losses are more difficult to assess. Examples of indirect losses are as follows: 1. Shutdown 2. Loss of Product 3. Loss of Efficiency 4. Contamination of Product 5. Overdesign • E.g: Replacement of corroded boiler or condenser tubes in a large power plant may require $1,000,000 or more per day for power purchased from inter-connected electric systems to supply customers while the boiler is down. Dr. MAS - NED UET Karachi - Pakistan 6
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- 8. Why corrosion occurs? • Corrosion of metal could be considered as extractive metallurgy in reverse as shown in figure. .. • Materials wants to go back to its stable thermodynamic state. Dr. MAS - NED UET Karachi - Pakistan 8
- 9. Corrosion • Corrosion = destruction and deterioration of engineering materials because of chemical or electrochemical reaction with its environment. • Materials = Metal. Polymer, Ceramics. Composite etc. • Environment = liquid or gases. Dr. MAS - NED UET Karachi - Pakistan 9
- 10. Examples • Rusting of steel and cast iron in water, including humid air, as occurs with domestic and industrial water tanks and supply piping, automobiles, and exposed steel structures. 10 Dr. MAS - NED UET Karachi - Pakistan
- 11. • Corrosion of Cu, Al, and cast Fe in automotive cooling systems. • Corrosion of iron-base, copper-base, nickel-base, etc. alloys in the chemical process industry. • Corrosion of automobile exhaust systems by direct reaction of the metal with high-temperature gases and by condensation of water and absorption of the oxides of sulfur and nitrogen to produce aqueous acid environments. • Enhanced deterioration of structural concrete and stone by interaction with condensed moisture and acidic contaminants in the air, such as the oxides of sulfur and nitrogen • Stress-corrosion cracking (SCC) of gold and brass by mercury Dr. MAS - NED UET Karachi - Pakistan 11
- 12. • Corrosion of turbine blades in gas turbines by hot combustion gases. • Corrosion of metallic surgical implant materials used in orthopedic, cardiovascular, and dental devices resulting in the release of metal ions to tissues, and • Degradation of the physical properties of polymeric implant materials due to interactions with tissue fluids and/or blood • Corrosion of iron-base and nickel-base alloys by liquid metals used as heat transfer agents (e.g., liquid sodium, potassium, and lithium). • Stress Corrosion Cracking (SCC) and pitting of stainless steel in sea water • SCC and pitting of stainless steel in sea water Dr. MAS - NED UET Karachi - Pakistan 12
- 13. Classification and Types of Corrosion • Wet and Dry. Dr. MAS - NED UET Karachi - Pakistan 13 Assignment: Submission date next Friday Hand written (4th Nov. 2022) Already studied in undergraduate
- 14. Corrosion as Electrochemical reaction Dr. MAS - NED UET Karachi - Pakistan 14
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- 17. Corrosion Testing Equipment • Electrochemical work station Dr. MAS - NED UET Karachi - Pakistan 17
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- 19. Dr. MAS - NED UET Karachi - Pakistan 19 Working Electrode: the study material
- 20. Dr. MAS - NED UET Karachi - Pakistan 20 Reference Electrode: Saturated Calomel Electrode, SCE
- 21. Dr. MAS - NED UET Karachi - Pakistan 21 Counter Electrode: Platinum or Graphite
- 22. What is Potential? Dr. MAS - NED UET Karachi - Pakistan 22
- 23. What is current ? Dr. MAS - NED UET Karachi - Pakistan 23
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- 30. Dr. MAS - NED UET Karachi - Pakistan 30 OCP Graphs
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- 32. Thanks Dr. MAS - NED UET Karachi - Pakistan 32