Cleaning and Corrosion

Question 1

Is there any requirement for cleaning an aircraft prior to an annual or 100 hour inspection?

Answer 1

It is not only good, common sense, but it is a legal requirement as specified in FAR Part 43, Appendix D.

Question 2

Discuss the general precautions that should be observed when washing an airplane.

Answer 2

Avoid or protect areas, which may be damaged or contaminated, such as pitot and static ports, hinges, sealed areas, and bearings.

Question 3

What are some of the more common light-duty cleaning agents?

Answer 3

Soap or detergents and water.

Question 4

What materials are commonly used as heavy duty cleaners?

Answer 4

Solvents and emulsions.

Question 5

What are the preferred cleaners for plastic surfaces such as windshields?

Answer 5

Mild soap and water or a manufacturer approved cleaner.

Question 6

What type of cleaning agents should be used to remove grease, oil or fuel from aircraft tires?

Answer 6

Soap and water

Question 7

Give at least three examples of the factors that cause or influence corrosion.

Answer 7

1 - Environmental conditions
2 - The presence of dissimilar metals
3 - The type of metal
4 - The presence of electrolytes or contaminates
5 - The condition of protective coatings

Question 8

Name at least 3 forms of corrosion

Answer 8

1 - Surface
2 - Intergranular 
3 - Filiform
4 - Galvanic (Dissimilar metal)
5 - Oxidation
6 - Pitting
7 - Stress
8 - Fretting

Question 9

Name at least one cause of filiform corrosion.

Answer 9

1 - Improper or incomplete curing of a wash primer prior to painting.
2 - Failure to completely wash off acidic surface contamination

Question 10

What are the visible signs of filiform corrosion?

Answer 10

Blistered paint surfaces or worm or thread-like tracks or patterns under the paint.

Question 11

What are the two primary factors that may cause the development of stress corrosion cracks?

Answer 11

A corrosive environment and sustained tensile stress.

Question 12

What are the visible signs of fretting corrosion?

Answer 12

The corrosion residue has a dark, smoky appearance and often appears around and streaming back from rivet heads.

Question 13

Why are piano-type hinges prime spots for corrosion?

Answer 13

The steel pin and aluminum hinge materials are dissimilar metals and the hinge design tends to trap moisture and contaminants.

Question 14

What is the best way to protect piano hinges from corrosion?

Answer 14

Keep them clean and properly lubricated.

Question 15

Provide at least four examples of procedures used to prevent corrosion.

Answer 15

1 - Cleaning
2 - Lubrication
3 - Treatment 
4 - Sealing
5 - Inspection
6 - Installing protective covers
7 - Keeping drain holes free and clear

Question 16

Describe the tools that should be used to remove corrosion from anodized aluminum surfaces.

Answer 16

Nylon scrubber pads such as Scotch-Brite, bristle brushes, aluminum wool, or aluminum wire brushes.

Question 17

Describe the effects of using steel brushes or steel wool to remove the corrosion from aluminum surfaces.

Answer 17

Steel brushes or steel wool must not be used to clean aluminum because steel particles can become embedded in the aluminum and cause corrosion.

Question 18

What is the purpose of Alodine?

Answer 18

Alodine is a chemical process that deposits a protective film on aluminum alloys. This film improves corrosion resistance and paint adhesion.

Question 19

For what reason should you avoid cleaning anodized aluminum surfaces with aluminum metal polish?

Answer 19

It should not be used on anodized surfaces because it will remove the oxide coat.

Question 20

Why should aircraft fabrics and plastics be cleaned only with recommended cleaners?

Answer 20

Recommended cleaners cause the least amount of deterioration or damage.

Question 21

List at least five examples of areas in an aircraft that prone to corrosion.

Answer 21

1 - Battery compartments
2 - Exhaust trail areas 
3 - Bilge areas
4 - Vent areas
5 - Landing gear and wheel wells
6 - Fuel tanks
7 - Wing flap recesses
8 - Around and below galleys and lavatories
9 - Piano hinges
10 - Any area that can trap water