30 Questions
What type of corrosion can occur when dissimilar metal skins are riveted together?
Galvanic corrosion
Where can galvanic corrosion take place?
Where dissimilar metal skins are riveted together
How does stress corrosion differ from intergranular corrosion?
Stress corrosion causes rapid crack growth at the end of a crack
What causes the dulling of the surface in surface corrosion?
Conversion of microscopic metal into corrosion salts
In which type of corrosion will there be a rather uniform attack over the entire surface area?
Surface corrosion
What happens if the deposits from surface corrosion are not removed and the surface remains unprotected?
Corrosion pits will form
What is the main purpose of using cadmium as a coating on steel hardware?
To improve resistance to corrosion fatigue
How can you identify corrosion on a cadmium-plated surface?
By observing white-to-brown-to-black mottling of the surface
Why is chromium used as a protective plating on parts?
To protect against wear and reclaim worn parts
In what way does cadmium protect steel when they are coupled together?
By forming a continuous oxide coating
What could be a consequence if a chromium-plated part shows cracks in the coating?
Origination of corrosion at the base metal below the separations
Which material is anodic when coupled with steel, providing protection through galvanic action?
Cadmium
What is the reason behind the dull grey-green discoloration seen on copper or copper alloy surfaces?
Formation of a fine-grained, airtight copper oxide crust
In what applications does silver tarnish, producing a brown-to-black film of silver sulphide?
Waveguides, miniature circuits, and RF shielding
Which metal is traditionally regarded as the best coating for corrosion resistance and solderability?
Gold
What accelerates the corrosion of copper when silver is plated over it?
Galvanic action at pinholes in silver plating
What happens when silver is plated over copper in the presence of pinholes or breaks in the plating?
Accelerated corrosion of copper
What is the cause of the tarnish seen on silver surfaces in the presence of sulphur?
Tarnishing by silver sulphide
What is the primary reason for scum formation along the edge of a seal in an integral fuel tank?
To cause a leak
Why are aluminium and its alloys widely used in aircraft construction?
Because they are highly anodic and can resist mild corrosive conditions
What is a common issue faced by aluminium alloys when exposed to certain conditions?
Pitting, intergranular corrosion, and stress corrosion cracking
Why does galvanic corrosion occur when aluminium comes into contact with other metals?
Because aluminium is highly anodic to most other metals
What is the role of the oxide film formed on aluminium under mild corrosive conditions?
To offer increased resistance to corrosion
In what way does fungus growth in a fuel tank relate to the corrosion characteristics of aircraft metals?
Fungus growth can impact the sealant of the tank leading to leaks
Why is tarnish removal critical on gold components?
To avoid darkening of reflecting surfaces
What effect does gold plating over silver or copper have on the less noble metals?
Promotes corrosion by accelerating it
What is the 'purple plague' mentioned in the text?
A brittle compound formed when bonding gold to aluminium
Why is tin commonly used in solder applications?
Due to its solderability and corrosion resistance
What issue arises from the growth of 'whiskers' on tin-plated wire?
Potential short-circuits or electrical failures
What is the main advantage of tin plating on avionic RF shields and filters?
Enhanced corrosion resistance
This quiz covers the concept of galvanic corrosion in metals, particularly when dissimilar metal skins are riveted together or when aluminium inspection plates are attached to structures with steel screws. Explore various scenarios and solutions related to galvanic corrosion.
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