Corrosion Flashcards
Intergrannular corrosion is often caused by
Improper heat treatment
Corrosion caused by electrolytic action is the result of
Contact between two unlike metals
Corrosion may be regarded as the destruction of metal by
Electrochemical action
Exfoliation corrosion could be referred to as
Layer corrosion
When dissimilar metals are brought together, or the same metal in different states, one metal forms the anode and the other the cathode. Which will suffer the corrosion?
The anode
In corrosion, the electrode that loses electrons is
Either the cathode or the anode depending upon the electrolyte
What is a common, ongoing cause of corrosion?
Spilled battery acid
What is stress corrosion?
Corrosion in an area under continuous loading
Electrochemical reaction is caused by the contact of
Moisture on the surface of an inert metal
Chemical attack is a direct result of
Cathodic and anodic changes in the material
Galvanic corrosion is caused by
The joining of 2 dissimilar metals
With reference to the galvanic series, the most noble of two metals in contact, will
Cause the less noble metal to corrode
Stress corrosion is associated with
A corrosion put in a member under stress
Corrosion will spread more rapidly when metals are exposed to
High temperatures
What is correct regarding chemical testing?
The chemical test for bronze is nitric acid which produces a white precipitate
All corrosion is a chemical reaction. True or false?
True
In a poorly produced repair to skin structure, where would stress corrosion start?
Radiate from the corner or sharp edges
Some metals are inherently stable. What does this suggest?
They strongly resist corrosion
The oxide film formed on the surface of the aluminium is
Non-porous
Corrosion control begins at the
Design stage
Aluminium is
Highly resistant to corrosion
When galvanic corrosion takes place, which part corrodes?
Anode
Corrosion caused by galvanic action is the result of
Contact between two unlike metals
What are the signs of fretting corrosion?
Black powder or cocoa staining
Black streaks from a rivet hole signify
Fretting
When a steel part is welded, corrosion occurs because
The strip has become anodic
Intergranular corrosion
May have no visual surface indication
Jointing compound is used for what reason?
To prevent dissimilar metal corrosion
The lifting of flaking of the metal at the surface due to delamination of grain boundaries caused by the pressure of corrosion is
Electrolysis
The electrolytic process that forms an oxide film on the surface of the surface of aluminium alloys is known as
Anodising
What is the indication of fretting corrosion on aluminium alloy
Black powder
What action is taken to protect integral tanks from corrosion due to microbiological growth?
A biocidal additive is used in the fuel
What type of corrosion attacks grain boundaries of aluminium alloys which are improperly or inadequately heat treated?
Intergranular corrosion
One of the processes which artificially produces a film of oxide on the surface of aluminium or its alloys is commonly called
Anodising
Intergranular corrosion in structural aluminium alloy parts
May be detected by the white, powdery deposit formed on the surface of the metal
OR
Cannot always be detecting by surface indications
Corrosion will spread more rapidly when metals are exposed to
High temperatures
Magnesium alloy components are protected by
A chemical process
Corrosion at the grain boundaries is called
Intergranular
Fretting corrosion occurs where
Two material are subject to very slight movement between the two
Spilled Mercury on aluminium
Reduces the corrosion resistance after time in contact
OR
Causes rapid and severe corrosion in short time period
The usual manufacturers anti-corrosion process to be applied to Fe aircraft parts is
Cadmium plating
To check the interior of tubular members for corrosion attack
Ultra sonic testing or x-ray is necessary
The form of corrosion most likely to cause stress concentration is
Pitting corrosion
Lead acid battery fluid has been found to be leaking on the surface of the aircraft structure. What substance would you use to neutralise the acid?
Sodium bicarbonate of soda
What colour is the corrosion found on the surface of aluminium alloys?
White/Grey
Corrosion on copper is identified by
Green discolouration
When examining a piece of metal through a magnifying glass, hair line cracks would indicate
Intergranular corrosion
Corrosion is always completely removed
To permit the extent of damage to be assessed
What is a temporary protective measure?
Chromating
Spilled Mercury on aluminium causes
Greyish powder, fuzzy deposit or whiskery growth
What are acceptable to use in cleaning anodised surfaces?
Aluminium wool, fibre bristle brush
Which of these materials is the most anodic; magnesium, cadmium or 7075-T6 aluminium alloy
Magnesium
Which of these materials is the most cathodic; 2024 aluminium alloy, zinc or stainless steel
Stainless steel
Galvanic corrosion is most likely to be most rapid and severe when
The area of the anode is smaller an the area of the cathode
OR
The area of the cathode and the anode are similar
What is the most cathodic; nickel, magnesium or stainless steel?
Stainless steel
