Cleaning & Corrosion Control

Question 0

Name three forms of corrosion.

Answer 0

Surface, dissimilar metal, intergranular, filliform, fretting.

Question 1

List three factors of corrosion.

Answer 1

Environmental, type of metal, dissimilar metals in contact, condition of protective coatings, presence of electrolytes and contaminants.

Question 2

List procedures in corrosion prevention maintenance.

Answer 2

Cleaning, lubrication, inspection, seal protective covers, and clear drain holes.

Question 3

Identify the areas of an aircraft that are most prone to corrosion.

Answer 3

Battery compartment, exhaust system and exhaust trails, wheel wells, lower area of the belly (bilge), piano hinges, areas of dissimilar metal contact, welded areas, inside of the fuel tanks especially integral tanks, metal fittings under high stress, lavatories and foodservice areas.

Question 4

What tools are proper for removing corrosion from aluminum alloy?

Answer 4

Aluminum wool or aluminum wire brushes. Severe corrosion may be removed with a rotary file.

Question 5

What are some necessary precautions during aircraft washing?

Answer 5

Avoid protected areas, bearings, hinges, sealed airs, and the pitot and static inlets.

Question 6

Name light duty cleaning agents.

Answer 6

Soap and synthetic detergents.

Question 7

Name heavy duty cleaning agents.

Answer 7

Solvents and emulsions.

Question 8

Where is stress corrosion most likely to occur on an aircraft?

Answer 8

In any metal component that is continually under a tensile stress. The metal around holes in castings that are fitted with pressed-in bushings are susceptible to stress corrosion.

Question 9

How may filliform corrosion look?

Answer 9

Blistered paint with worm or fern like patterns.

Question 10

What is used to clean transparent plastic windshields and windows of an aircraft?

Answer 10

Mild soap and plenty of clean water.

Question 11

Why should aluminum polish not be used on anodized surfaces?

Answer 11

The polish removes the protective oxide coating.

Question 12

What is used to clean aircraft tires?

Answer 12

Soap and water.

Question 13

Why should you use only the recommended cleaner on fabric and plastics?

Answer 13

They cause less deterioration.

Question 14

Where is filiform corrosion most likely to occur on an aircraft?

Answer 14

Under a dense coating of topcoat enamel such as polyurethane. Filiform corrosion is caused by improperly cured primer.

Question 15

Why clean before inspection?

Answer 15

To remove residues that could be hiding potential problems.

Question 16

Why do piano hinges corrode easily?

Answer 16

Dissimilar metals are used in fabrication, and the basic design traps contaminants.

Question 17

How should corrosion be minimized at piano hinges?

Answer 17

They should be kept as clean and dry as practicable and lubricated with a low viscosity moisture dispersing agent.

Question 18

What can be used to repair the anodized surface of an aluminum alloy part?

Answer 18

A chemical conversion coating such as Alodine.

Question 19

Should you use steel wool on aluminum? Why or why not.

Answer 19

No, causes corrosion.

Question 20

What is Alodine used for?

Answer 20

It provides the oxide coat to protect aluminum alloy surfaces, and is also used as a substrate to help paint bond.

Question 21

Where is fretting corrosion most likely to occur on an aircraft?

Answer 21

In a location where there is a slight amount of relative movement between two components, and no way for the corrosive residue to be removed as it forms. Fretting corrosion around rivets in a skin is indicated by dark deposits streaming out behind the rivet heads.

Question 23

Where is dissimilar metal corrosion most likely to occur on an aircraft?

Answer 23

Anywhere different types of metal come in contact with each other, especially where moisture is present; for example, piano hinges.

Question 24

What must be done to a piece of aluminum alloy to remove surface corrosion and to treat the metal to prevent further corrosion?

Answer 24

Remove the corrosion residue with a bristle brush or a nylon scrubber. Neutralize the surface with chromic acid or with some type of conversion coating. Protect the surface from further corrosion with a coat of paint.

Question 25

What is used to keep corrosion from forming on structural aluminum alloy?

Answer 25

An oxide coating or aluminum cladding.

Question 26

How may rust be removed from a highly stressed metal part?

Answer 26

By glass bead blasting, by careful polishing with mild abrasive paper or by using fine buffing compound on a cloth buffing wheel.

Question 27

What is used to neutralize the electrolyte from a lead-acid battery that has been spilled on an aircraft structure?

Answer 27

A solution of bicarbonate of soda and water.

Question 28

What is used to neutralize the electrolyte from a nickel-cadmium battery that has been spilled on an aircraft structure?

Answer 28

A solution of boric acid and water, or vinegar.

Question 29

What solvent is recommended for removing grease from aircraft fabric prior to doping it?

Answer 29

Methyl Ethyl Ketone (MEK) or lacquer thinner.

Question 30

What type of device is used to remove surface corrosion from a piece of magnesium alloy?

Answer 30

A stiff hog-bristle brush.

Question 31

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

Answer 31

The tubing is filled with hot linseed oil and then drained.

Question 37

Where is intergranular corrosion most likely to occur on an aircraft?

Answer 37

Along the grain boundaries of aluminum alloys that have been improperly heat-treated. Extruded aluminum alloy is susceptible to intergranular corrosion.