Corrosion Flashcards
1
Q
How does dry corrosion occur
A
- Occurs through chemical reactions of metals or alloys with gases, in furnaces at high temperatures
- Caused by the reaction of the metal with oxygen
2
Q
How does wet corrosion occur
A
- Occurs when a metal is placed into a fluid, usually an electrolyte (a solution containing ions which carry electric charges)
3
Q
What is uniform attack
A
- When a metal undergoes wet corrosion, some parts become anodic while others become cathodic
- When the locations of the cathode and anode continually change, it is called uniform attack
4
Q
What is galvanic attack
A
- When dissimilar metals are placed together in a corrosive environment, galvanic attack will occur.
- One of the metals becomes cathodic and the other becomes anodic due to the difference in affinity to corrosion
5
Q
Which metals are the most suitable for a sacrificial anode
A
- Zinc, Magnesium and Aluminium are the most commonly used
6
Q
Do areas of high stress become anodic or cathdoic?
A
- Areas of high stress will become anodic
- These areas are called stress cells
7
Q
Describe galvanising
A
- Involves dipping steel pieces into molten zinc as it will cover it and protect it from corrosion
- The zinc coating will slowly corrode away but the metal underneath will be completely safe from corrosion
8
Q
What is cathodic protection
A
- Metals are made from cathodic steels to protect it from corroding
9
Q
How do sacrificial anodes act as a form of protection against corrosion
A
- Blocks of sacrifical anodes are bolted onto the metal which would normally corrode
- Instead of the metal corroding, these more reactive materials will make corrode instead and make the metal cathodic
10
Q
What is Impressed Current Cathodic Protection (ICCP)
A
- The use of a current to reverse the electrical flow associated with corrosion which will make the object ICCP is being used on a cathode
- Used mainly for pipelines and long structures where sacrificial anodes will prove to be ineffective
