1
Q
What is corrosion
A
Chemical or electrochemical reactions cause metals to be oxidised, forming salts and oxides of the metal.
2
Q
Galvanic Corrosion
A
- 2 dissimilar metals make electrical contact in the presence of an electrolyte
- metals from less noble group corrode easier when in contact with more noble metals
3
Q
Electrolytic corrosion
A
- Due to an electrolyte and the flow of electrical current between 2 metals
- casued by electromotive force (EMF)
4
Q
What is a microbiological attack?
A
-bacteria, fungi or moulds (commonly found in aircraft fuel tanks and are the greatest corrosion problems)
5
Q
Microbial corrosion can be minimised by?
A
- scheduled drainage of water from fuel tanks
- inspections for bacteria, remove bacteria after
- application to prevent further growth
6
Q
Examples of where microbial corrosion can occur?
A
- fuel tanks
- toilets
- galleys
- bilge sump
7
Q
What is the common place for stress corrosion
A
Between rivets in a stressed skin
8
Q
Filiform corrosion?
A
- humidity 78% - 90%
- special form of oxygen-concentration cell corrosion
- if not removed, it can lead to inter-granular corrosion, especially around fasteners + seams
- worm like trace beneath paint film
9
Q
Pitting corrosion?
A
- produces holes in material
- common on aluminium and magnesium
- decreases materials strength
10
Q
Inter-granular corrosion?
A
- cracking and tends to accelerate over time
11
Q
Exfoliation Corrosion?
A
- advanced form of inter-granular corrosion
12
Q
Fretting corrosion?
A
- erosion corrosion which occurs due to vibration and slipping
- rubbing action removes protective film, continued rubbing leads to active metal released in atmosphere
- use lubrication to help reduce friction
13
Q
Mercury Corrosion?
A
- small amounts can lead to serious corrosion problems
- attacks aluminium through a chemical reaction (amalgamation)
- dangerous to aircraft + people
14
Q
What is the cause of corrosion
A
- deterioration of metal due to reaction between different metals and their operational environment
- thicker components are more prone to corrosion due to variation in their composition
15
Q
Noble metals
A
- such as silver, gold, platinum
- resistance to surface attack and their improved electrical and thermal conductivity
16
Q
Wet corrosion
A
- where relative humidity is >60%
17
Q
Corrosion prone areas?
A
- exhaust area, battery compartment, lavatories and galleys, bilge areas, wheel well and landing gear area, external skin areas,
