29 Questions
What is the chemical process through which mercury attacks aluminium?
Amalgamation
In what way does mercury attack aluminium along grain boundaries?
Rapidly
Why does the anode give up electrons more easily when it is smaller than the cathode?
Due to increased surface area
What effect does the chemical reaction of mercury on aluminium have in an aeroplane?
Complete destruction of aluminium
Which of the following metals is NOT commonly found in any quantity around aircraft?
Magnesium
What is the corrosion product of aluminium?
White-to-grey powdery material
What is the protective coating applied to some aluminium parts?
Aluminium oxide film
What is the effect of anodising on the thickness of the oxide film on aluminium?
Increases the thickness
What should be avoided to prevent unnecessary destruction of an anodised surface?
Nicks and scratches
Which metal is noted for being highly susceptible to corrosion when exposed without a protective finish?
Magnesium
What happens to magnesium corrosion deposits over time?
They raise slightly and spread rapidly
What is the main cause of fretting corrosion?
Destruction of the protective film by rubbing action
In fretting corrosion, why does debris act as an abrasive?
It gets trapped between surfaces due to minimal movement
How is fretting corrosion visually signaled around rivets in a skin?
Dark deposits around the rivet heads
What distinguishes exfoliation corrosion from other forms of corrosion?
It mainly occurs in extruded materials with laminar grain structure
What is a characteristic feature of exfoliation corrosion?
'Peeling away' effect along grain boundaries
Why does exfoliation corrosion primarily affect extruded materials?
Due to their laminar grain structure
What is the purpose of cadmium as a coating on high-strength steel parts?
To improve resistance to corrosion fatigue
How can one identify corrosion on cadmium plating?
By the presence of white-to-brown-to-black mottling on the surface
In what way does chromium protect underlying metal when used as a protective plating?
By forming a continuous oxide coating
What is the protective function of chromium coatings with cracks?
It still protects the base metal below these separations
What happens when cadmium is coupled with steel in terms of galvanic action?
It protects the steel by galvanic action
How does cadmium behave when it shows mottling and cracks in the plating?
It still performs its protective function as an anodic material
What causes the tarnish on silver surfaces?
Silver sulphide
In what way does gold provide benefit when used as a coating?
Improved corrosion resistance and solderability
How does the tarnish on silver surfaces affect circuit electrical characteristics?
Does not affect electrical characteristics
What material is silver usually plated over in circuits?
Nickel
What accelerates the corrosion of copper when silver is plated over it?
Galvanic action
What color does tarnish on silver surfaces typically appear as?
Brown-to-black
Test your knowledge on the chemical reaction between mercury and aluminum in aircraft, specifically focusing on how mercury rapidly attacks along the grain boundaries and destroys the aluminum. Learn about the dangers of mercury corrosion in aeroplanes.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
