Corrosion Prevention Flashcards
What are the 6 steps of preventing uniform corrosion?
1) Provide a corrosion allowance ie. use thicker material
2) Select an alternative material
3) Change the environment if possible ie. cold temperatures slow corrosion
4) Add a corrosion inhibitor
5) Use cathodic protection
6) Apply a coating
What are the 2 types of cathodic preotection?
1) Sacrificial anode
2) Impressed current
What are the 7 things that have to be considered when applying a protective coating to a material?
1) Chemical resistance
2) Proper adhesion
3) How the coating will expand and contract with temperature changes
4) Abrasion resistance
5) Aging resistance
6) Water resistance
7) The ease of application
What are some ways that galvanic corrosion can be prevented?
1) Use a 3rd material that is anodic to the 2 protected materials
2) Avoid using dissimilar metals
3) Insulate dissimilar metals
4) Use impressed currents
5) Apply coatings
6) Use an inhibitor
How can crevice corrosion be prevented?
1) Use welds or coatings to eliminate crevices
2) Avoid packing material that absorbs moisture
3) Ensure complete drainage in tanks
4) Avoid sharp corners
How can pitting corrosion be prevented?
1) Apply coatings
2) Use inhibitors
3) Maintain surfaces to be smooth
4) Choose materials wisely
How can intergranular corrosion be controlled?
1) Select materials wisely
2) Control chemical compositions
3) Add stabilizer elements to a material
4) Control welding parameters
How can selective leaching corrosion be prevented?
Addition of alloying elements
How can stress cracking corrosion be preveted?
1) Reduce the stress
2) Apply coatings
3) Use inhibitors
4) Change the material
5) Use cathodic protection
How can hydrogen induced cracking be prevented?
1) Use steel with low levels of impurity
2) Use heat treatment to remove hydrogen
3) Modify the environment to reduce hydrogen charging
4) Use materials lower in hardness
What is the difference between impressed current and sacrificial anode methods?
Impressed current forces an electric current through a material making it cathodic so that it cannot corrode.
Sacrificial anode uses a material that is less noble (more likely to corrode) and forces it to donate electrons to the cathode
How can erosion corrosion be prevented?
1) Shot peening
2) Surface hardening
3) Design alterations
