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 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.
Bearings.

Question 3

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

Answer 3

Soap.
Detergents.
Water.

Question 4

What materials are commonly used as heavy duty cleaners?

Answer 4

Solvents
Emulsions.

Question 5

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

Answer 5

Mild soap and water.
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 caused or influence corrosion.

Answer 7

Environmental conditions.
Dissimilar metals.
Type of metal.
Presence of electrolytes or contaminants.
Condition of protective coatings.

Question 8

Name at least three forms of corrosion.

Answer 8

Surface.
Intergranular.
Filiform.
Dissimilar metal/galvanic.
Oxidation.
Pitting.
Stress.
Fretting.

Question 9

Name at least one cause of filiform corrosion.

Answer 9

Improper curing of a wash primer prior to painting.
Failure to completely wash off acidic surface contamination.

Question 10

What are the visible signs of Filliform corrosion?

Answer 10

Blistered paint surfaces.
Worm or thread, like tracks or patterns under the paint.

Question 11

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

Answer 11

A corrosive environment.
Sustained tensile stress.

Question 12

What are the visible signs of fretting corrosion?

Answer 12

A dark smoky appearance that 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 material are dissimilar metals.
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

Cleaning.
Lubrication.
Treatment.
Sealing.
Inspection.
Installing protective covers.
Keeping drainholes free and clear.

Question 16

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

Answer 16

Nylon scrubber pads (Scotch Brite).
Bristle brushes.
Aluminum wool.
Aluminum wire brushes.

Question 17

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

Answer 17

Steel particles can become embedded in the aluminum and cause corrosion.

Question 18

What is the purpose of Alodine?

Answer 18

It is a chemical process that deposits, a protective film on aluminum alloys.
It 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 will remove the anodized layer.

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 are prone to corrosion.

Answer 21

Battery compartment.
Exhaust trail areas.
Bilge areas.
Vent areas.
Landing gear and wheel wells.
Fuel tanks.
Wing flap recesses.
Around and below lavatories.
Piano hinges.
Any area that can trap water.