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Flashcards in Corrosion Deck (28):
1

Metal corrosion

the deterioration of the metal by chemical or electrochemical attack.

2

three conditions necessary for corrosion to occur?

the presence of an electrolyte, an anode and a cathode and a conductor.

3

Electro-chemical attack?

the process of one metal giving up electrons (anode) to another metal (cathode). To replace the electrons the anode loses, it gains them from the electrolyte. The anode corrodes the cathode does not.

4

direct chemical attack?

occurs when a caustic agent comes in direct contact with the bare surface metal and produces corrosive by products.

5


What is an Electro-chemical attack comparable with? Why?

An electro-chemical attack is comparable with a dry cell battery because both have an electrolytic reaction.

6

What is an anode?
.


the positive plate that gives up electrons to the cathode and corrodes.

7


What is a cathode?

the negative plate that gains electrons from the anode

8

What can a mechanic do to prevent corrosion from ever occurring?

by using a protective coating, adequate cleaning, keeping drain holes free of obstructions, and sealing the aircraft against water during foul.

9

Uniform Surface corrosion

An even dulling of the surface caused by exposure to corrosive agents.

10

Pitting corrosion

Next step after uniform surface. Pits or clumps of white powder appear on anodic area

11

Inter-granular corrosion

Internal corrosion along grain boundaries

12

Exfoliation corrosion

An extreme case of intergranular corrosion that causes metal layers to delaminate

13

Galvanic corrosion

Occurs When two dissimilar metals with different potentials come into direct contact and set off an electron flow.

14

Concentration Cell corrosion

Occurs when two metals are joined together and moisture settles in creating a corrosion cell.

15

Stress corrosion

Occurs When a metal is subjected to a tensile stress in a corrosive environment.

16

Fretting corrosion

Occurs when slight movements wear away small particles of metal on two tightly fitted surfaces

17

six causes of corrosion

Wind erosion
Air moisture
Salt water
Spilled battery acids
Caustic cleaning solutions.
Improper heat treatment

18

Name ten areas where corrosion is likely to form on an aircraft.

Exhaust trails
Bilge areas
Wheel wells
Exterior skins
Galleys
Battery compartments
Lavatories
Flap recesses
Seat tracks
Fuel tanks

19

What are the steps in treating aluminum alloy of corrosion?

Fine clean parts
Strip paint
Remove corrosion with powdered pumice and scotch brite pad. For severe corrosion, use an aluminum wire brush
Neutralize remaining corrosion salts with 5% chromic acid solution
rinse off after 5 minutes.
Restore the parts protective coating.

20

Name the various protective coatings available for aluminum alloys.

Alclad
Alodine
Anodizing
Organic Coatings

21

How are ferrous metals treated of corrosion

strip parts of dirt and paint
Remove corrosion mechanically with scotchbrite and steel wire brush
Restore protective coating

22

Name the various protective coatings available for ferrous metals

Galvanizing with a coat of zinc
Cadmium plating
Metal spraying with molten aluminum
Case Hardening.

23

How is magnesium treated of corrosion?

with a hog bristle brush, nylon pad or glass bead blasting.

24

How can galvanic corrosion be prevented?

By placing a dielectric tape

25

How is the inside of structural steel tubing protected against corrosion?

Using Hot linseed oil

26

How is corrosion treated on highly stressed steel parts? Why?

with the use of abrasive papers, small power buffers and buffing compounds

27

What is the most likely cause of intergranular corrosion?


The most likely cause of intergranular corrosion is improper quenching during the heat treatment process.

28

An anodized surface which has been broken can be repaired by which chemical
treatment?

by a chemical conversion material such as Alodine.