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Questions and Answers
What are the 4 basic elements required for corrosion to happen?
Anode, Cathode, Electron flow, Path
Where is the anode located in the corrosion of steel under a drop of water?
Fe
What is the corrosion mechanism for Carbon Steel as described in the content?
Fe → Fe2+ + 2e : anode; O2 + 2H2O + 4e → 2OH- : cathode; Fe2+ + 2OH- → Fe(OH)2 : insoluble hydroxide
What are the main methods mentioned in the content to control corrosion?
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What is meant by damage mechanism as explained in the content?
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Study Notes
Corrosion Mechanism
- Corrosion requires four basic elements: anode, cathode, path, and electron flow
- The anode is where oxidation occurs, and the cathode is where reduction occurs
Corrosion of Steel
- The corrosion mechanism for carbon steel involves two half-reactions:
- Anode: Fe → Fe2+ + 2e
- Cathode: O2 + 2H2O + 4e → 2OH-
- Overall reaction: Fe2+ + 2OH- → Fe(OH)2 (insoluble hydroxide, white-green)
Rust Formation
- Fe(OH)2 can further react to form different types of rust:
- Fe(OH)3 (black magnetite)
- γ-Fe3O4 (brown rust)
- γ(FeOOH) (yellow rust)
- Fe2O3 (reddish-brown rust)
Controlling Corrosion
- Methods to control corrosion include:
- Material selection and design
- Corrosion inhibitors and monitoring
- Coatings and linings
- Cathodic protection
Damage Mechanisms
- Damage mechanisms are processes that result in asset degradation, including corrosion
- Some damage mechanisms occur before or after an asset is put into service
- Examples of damage mechanisms include:
- Hydrogen attack, including:
- High-temperature hydrogen attack (HTHA)
- Hydrogen embrittlement (HE)
- Hydrogen blistering
- Hydrogen-induced cracking (HIC)
- Stress-oriented hydrogen-induced cracking (SOHIC)
- Hydrogen attack, including:
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Description
This quiz covers the basics of corrosion, including the mechanism and theory of corrosion, the behavior of metals in different environments, and the identification of the 4 basic elements necessary for corrosion to occur.
