Fill in th blanks
1. Cleaning
2. Uniform
3. surface
4. protective
5. Galvanic
6. corrosion, treatments
7. Chemical
8. Aluminum
9. Zinc-rich 10. MIL-PRF-85570
True or False
1. False
2. True
3. False
4. True
5. True
6. False
7. True
8. False
9. False
10. False
Knowledge Application
1. Uniform, pitting, galvanic and intergranular corrosion
2. 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 fuel tanks especially integral tanks, metal fittings and under high stress, lavatories and foodservice areas.
3. Under a dense coating of topcoat enamel such as polyurethane. Filiform corrosion is caused by improperly cured primer.
4. 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.
5. Along the grain boundaries of aluminum alloys that have been improperly heat-treated. Extruded aluminum alloy is susceptible to intergranular corrosion.
6. Anywhere different types of metal come in contact with each other, especially where moisture is present.
7. 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.
8. 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.
Multiple Choices
1. a
Some nonapproved commercial cleaning compounds can cause a chemical reaction with some of the metals used in aircraft structure. This reaction releases hydrogen gas that can be absorbed into the metal and cause hydrogen embrittlement which weakens the metal and can cause cracking and failure.
2. c
Magnesium engine parts are cleaned by washing them with a commercial solvent such as naphtha or Stoddard solvent, then soaking them in a decarbonizer that has been proven safe for magnesium. Any hard deposits that are not removed by this treatment can be removed with a scraper or with a grit blast.
3. b
An anodized coating is an electrolytically deposited film of oxide that covers the surface of the metal and keeps air and moisture away from it. If this coating is damaged, the metal can corrode.
Damaged anodized coating can be repaired by treating the damaged area with a chemical conversion coating material such as Alodine. This chemical treatment forms a hard oxide film on the surface much like the anodized surface.
4. b
Alodine can be applied to a surface after all traces of corrosion have been removed. The surface should be chemically cleaned until it supports an unbroken water film. Any breaks in the film of rinse water show that there some wax, grease, or oil on the surface, and further cleaning must be done.
5. a
Aliphatic naptha is a petroleum product between gasoline and kerosine in its characteristics. It is well suited for use as a cleaning agent for removing fingerprints, dust, and oily deposits that have settled on a surface to prepare the surface for painting.
Dry-cleaning solvent, such as Stoddard solvent, leaves a slight residue on the surface that can interfere with the adhesion of the paint.
Aromatic naptha is a coal tar derivative that is toxic and attacks acrylics and rubber products. It is not suitable for wiping down a surface before painting.
6. a
An area that has been affected by the electrolyte from a nickel-cadmium battery should be washed and neutralized with ammonia or a boric acid solution, allowed to dry thoroughly, then painted with an alkali-resisting varnish.
7. a
When cleaning and/or depainting an aircraft surface with a flammable agent, use only a cotton wiping cloth or a natural bristle brush. Synthetic fibers tend to create unsafe charges of static electricity that could ignite the flammable agent.
Emulsion-type cleaning agents may be applied to the surface with atomizing spray equipment. After the agent has penetrated the dirt or exhaust residue, it is scrubbed with a natural bristle brush and washed from the surface.
8. a
Aliphatic naphtha is the only one of the three materials listed here that will not damage rubber or acrylic plastic. Be sure that aromatic naphtha (a coal tar derivative) is not used.
9. b
Fayed surfaces are the parts of a structure that are covered in a lap joint. It is important when a structure is chemically cleaned that the fayed surfaces be protected so that corrosive materials do not seep between the sheets in the lap joints. This would cause corrosion to form in an area where it is hard to detect.
10. c
Aluminum alloys such as those used in an aircraft structure are reactive metals. This means that they are likely to react with chemicals to form salts (corrosion). Many caustic cleaning products react with aluminum alloy and cause them to corrode.
1. Cleaning
2. Uniform
3. surface
4. protective
5. Galvanic
6. corrosion, treatments
7. Chemical
8. Aluminum
9. Zinc-rich 10. MIL-PRF-85570
True or False
1. False
2. True
3. False
4. True
5. True
6. False
7. True
8. False
9. False
10. False
Knowledge Application
1. Uniform, pitting, galvanic and intergranular corrosion
2. 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 fuel tanks especially integral tanks, metal fittings and under high stress, lavatories and foodservice areas.
3. Under a dense coating of topcoat enamel such as polyurethane. Filiform corrosion is caused by improperly cured primer.
4. 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.
5. Along the grain boundaries of aluminum alloys that have been improperly heat-treated. Extruded aluminum alloy is susceptible to intergranular corrosion.
6. Anywhere different types of metal come in contact with each other, especially where moisture is present.
7. 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.
8. 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.
Multiple Choices
1. a
Some nonapproved commercial cleaning compounds can cause a chemical reaction with some of the metals used in aircraft structure. This reaction releases hydrogen gas that can be absorbed into the metal and cause hydrogen embrittlement which weakens the metal and can cause cracking and failure.
2. c
Magnesium engine parts are cleaned by washing them with a commercial solvent such as naphtha or Stoddard solvent, then soaking them in a decarbonizer that has been proven safe for magnesium. Any hard deposits that are not removed by this treatment can be removed with a scraper or with a grit blast.
3. b
An anodized coating is an electrolytically deposited film of oxide that covers the surface of the metal and keeps air and moisture away from it. If this coating is damaged, the metal can corrode.
Damaged anodized coating can be repaired by treating the damaged area with a chemical conversion coating material such as Alodine. This chemical treatment forms a hard oxide film on the surface much like the anodized surface.
4. b
Alodine can be applied to a surface after all traces of corrosion have been removed. The surface should be chemically cleaned until it supports an unbroken water film. Any breaks in the film of rinse water show that there some wax, grease, or oil on the surface, and further cleaning must be done.
5. a
Aliphatic naptha is a petroleum product between gasoline and kerosine in its characteristics. It is well suited for use as a cleaning agent for removing fingerprints, dust, and oily deposits that have settled on a surface to prepare the surface for painting.
Dry-cleaning solvent, such as Stoddard solvent, leaves a slight residue on the surface that can interfere with the adhesion of the paint.
Aromatic naptha is a coal tar derivative that is toxic and attacks acrylics and rubber products. It is not suitable for wiping down a surface before painting.
6. a
An area that has been affected by the electrolyte from a nickel-cadmium battery should be washed and neutralized with ammonia or a boric acid solution, allowed to dry thoroughly, then painted with an alkali-resisting varnish.
7. a
When cleaning and/or depainting an aircraft surface with a flammable agent, use only a cotton wiping cloth or a natural bristle brush. Synthetic fibers tend to create unsafe charges of static electricity that could ignite the flammable agent.
Emulsion-type cleaning agents may be applied to the surface with atomizing spray equipment. After the agent has penetrated the dirt or exhaust residue, it is scrubbed with a natural bristle brush and washed from the surface.
8. a
Aliphatic naphtha is the only one of the three materials listed here that will not damage rubber or acrylic plastic. Be sure that aromatic naphtha (a coal tar derivative) is not used.
9. b
Fayed surfaces are the parts of a structure that are covered in a lap joint. It is important when a structure is chemically cleaned that the fayed surfaces be protected so that corrosive materials do not seep between the sheets in the lap joints. This would cause corrosion to form in an area where it is hard to detect.
10. c
Aluminum alloys such as those used in an aircraft structure are reactive metals. This means that they are likely to react with chemicals to form salts (corrosion). Many caustic cleaning products react with aluminum alloy and cause them to corrode.
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