Materials And Corrosion Chap 6 Flashcards
Metals and alloys in aircraft should conform to …
How are metals and alloys identified
Colour codes
What do the British measure in
Standard wire gauge
What do french measure in
mm
What do Americans measure in
1000th of an inch
Def stan
Most frequently used in MOD
Conformity
A certificate to prove that the materials used are good quality
What is the colour coding
Used for rapid identification not to be used as sole means of identification
How are gauge sheets marked
Printed with ink on the surface
Ferrous metals
Contains mostly iron
Non-Ferrous metals
Contains no iron
Annealing
Changes the metal into a soft condition
Heat treatment
Metal is quenched and gives the metal specific properties
Refrigerated storage
Slows down the natural age process
Artificially age treatment
Precipitation (accelerated) treatment to get the maximum strength
Natural age process
Occurs at room temperature
Environmental damage
Includes corrosion, erosion and degradation of surface finish.
Prevention = coatings, tapes and corrosion prevention compounds
What does corrosion lead too
Reduce static strength, stress corrosion cracking, shortens fatigue life
Composite structure gets affected by what ? (4)
Fuels oils lubricants and UV light
Permanent coating
Includes paint
Supplementary protective
Temporary
Eg PX24
Iron and steel corrosion what do you see
Red rust deposits
What do you see with Aluminium and magnesium alloys corrosion
White to grey powdery deposits (magnesium is fluffy)
Most common
Surface corrosion
Sea air
Exhaust gases
Funnel smoke
Pitting corrosion
Local damage
Contamination
Surface protection is damaged
Fault
Thermal procedure changes
Intergranular corrosion
Very little to no external indication
Stress corrosion
Cause cracks
Fatigue corrosion
Cyclic stress from external load
Cracks
Fretting corrosion
Two heavily loaded materials run together
Removes natural protection
Crevice corrosion
High ratio of cathode to anode area
Collects dust and moisture
Filiform corrosion
Starts at fasteners
Under the paint
Not very visible
Damage is shallow and not very dangerous
Exfoliation or layer corrosion
Causes lifting of the metal surface
Extensive damage can occur
Electrochemical corrosion
Most usual type
Electrolytic effect
Two materials which touch liquid
Zinc copper
Husbandry procedures
Keep aircraft clean
Keep aircraft dry
Maintain protective coatings
Erosion
Loss of material from aircraft components by small particles such as grit, sand, stones, ice and water
How can you reduce erosion
Use of tape, anti-erosion paints suitable operation procedures
High temperature environments
Desert
Arid salt
Hot humid
Consequences of corrosion
Reduction in static strength
Stress corrosion cracking
Shortening of fatigue life
What are the two Corrosion removal processes
Mechanical
Chemical
Pre treatment for corrosion
Clean the surface
Paint again
Don’t leave it to long cause clean surface could deteriorate again
Removal of acid
Solution of 10% by weight
Sodium bicarbonate
PH level
Between 5-9
Removal of alkali
5% by weight
Solution of chromic acid
Removal of micro organisms
Deposits removed with bristle brush
Cleaned with hot water 50*C
