A primary reason why ordinary or otherwise nonapproved cleaning compounds should not be used when washing aircraft is because their use can result in hydrogen embrittlement in metal structures. hydrogen embrittlement in nonmetallic materials. a general inability to remove compound residues.
How may magnesium engine parts be cleaned? Soak in a 20 percent caustic soda solution. Spray with MEK (methyl ethyl ketone). Wash with a commercial solvent, decarbonize, and scrape or grit blast.
When an anodized surface coating is damaged in service, it can be partially restored by applying a thin coat of zinc chromate primer. chemical surface treatment. use of a suitable mild cleaner.
For which of the following reasons would a water break test be conducted? To make certain that a newly alodized aluminum surface is sufficiently coated. To make certain that a bare metal surface is thoroughly clean. To make certain that an anodizing coating has been sufficiently removed before an electrical bonding connection can be made.
Select the solvent recommended for wipedown of cleaned surfaces just before painting. Aliphatic naptha. Dry-cleaning solvent. Aromatic naptha.
Nickel-cadmium battery cases and drain surfaces which have been affected by electrolyte should be neutralized with a solution of boric acid. sodium bicarbonate. potassium hydroxide.
Which of the following are acceptable to use when utilizing chemical cleaning agents on aircraft?
1. Synthetic fiber wiping cloths when using a flammable agent.
2. Cotton fiber wiping cloths when using a flammable agent.
3. Atomizing spray equipment. 2 and 3. 1. 2.
Select the solvent used to clean acrylics and rubber. Aliphatic naphtha. Methyl ethyl ketone. Aromatic naphtha.
Fayed surfaces cause concern in chemical cleaning because of the danger of forming passive oxides. entrapping corrosive materials. corrosion by imbedded iron oxide.
Caustic cleaning products used on aluminum structures have the effect of producing passive oxidation. improved corrosion resistance. corrosion.
Fretting corrosion is most likely to occur when two surfaces fit tightly together but can move relative to one another. only when two dissimilar metals are in contact. when two surfaces fit loosely together and can move relative to one another.
The rust or corrosion that occurs with most metals is the result of a tendency for them to return to their natural state. blocking the flow of electrons in homogenous metals, or between dissimilar metals. electron flow in or between metals from cathodic to anodic areas.
Which of the following are the desired effects of using Alodine on aluminum alloy?
1. A slightly rough surface.
2. Relieved surface stresses.
3. A smooth painting surface.
4. Increased corrosion resistance. 3 and 4. 1, 2, and 4. 1 and 4.
Which of the listed conditions is NOT one of the requirements for corrosion to occur? The presence of an electrolyte. Electrical contact between an anodic area and a cathodic area. The presence of a passive oxide film.
The lifting or flaking of the metal at the surface due to delamination of grain boundaries caused by the pressure of corrosion residual product buildup is called brinelling. granulation. exfoliation.
A nonelectrolytic chemical treatment for aluminum alloys to increase corrosion resistance and paint-bonding qualities is called anodizing. alodizing. dichromating.
Which of the following are acceptable to use in cleaning anodized surfaces?
1. Steel wool.
2. Brass wire brush.
3. Aluminum wool.
4. Stainless steel wire brush.
5. Fiber bristle brush. 1, 3, & 5. 2 & 4. 3 & 5.
Intergranular corrosion in aluminum alloy parts may be detected by surface pitting, and white, powdery deposit formed on the surface of the metal. commonly appears as threadlike filaments of corrosion products under a dense film of paint. cannot always be detected by surface indications.
Which of the following may not be detectable even by careful visual inspection of the surface of aluminum alloy parts or structures? Filiform corrosion. Intergranular corrosion. Uniform etch corrosion.
What may be used to remove corrosion from highly stressed steel surfaces? Steel wire brushes. Fine-grit aluminum oxide. Medium-grit carborundum paper.
A primary cause of intergranular corrosion is improper heat treatment. dissimilar metal contact. improper application of primer.
Corrosion should be removed from magnesium parts with a stiff, nonmetallic brush. silicon carbide brush. carborundum abrasive.
Why is it important not to rotate the crankshaft after the corrosion preventive mixture has been put into the cylinders on engines prepared for storage? Fuel may be drawn into one or more cylinders and dilute or wash off the corrosion preventive mixture. The seal of corrosion preventive mixture will be broken. Engine damage can occur from hydraulic lock.
Which of the following is an acceptable first step procedure to help prevent scratching when cleaning a transparent plastic surface? Gently wipe the surface with a clean, dry, soft cloth. Flush the surface with clean water. Gently wipe the surface with a clean, soft cloth moistened with de-mineralized or distilled water.
What should be done to prevent rapid deterioration when oil or grease come in contact with a tire? Wipe the tire thoroughly with a dry cloth, and then rinse with clean water. Wipe the tire with a dry cloth followed by a washdown and rinse with soap and water. Wipe the tire with a cloth dampened with aromatic naphtha and then wipe dry with a clean cloth.
Galvanic corrosion is likely to be most rapid and severe when the surface area of the cathodic metal is smaller than surface area of the anodic metal. the surface areas of the anodic and cathodic metals are approximately the same. the surface area of the anodic metal is smaller than the surface area of the cathodic metal.
Corrosion caused by galvanic action is the result of excessive anodization. contact between two unlike metals. excessive etching.
Which of these materials is the most anodic? Cadmium. 7075-T6 aluminum alloy. Magnesium.
The interior surface of sealed structural steel tubing would be best protected against corrosion by which of the following? Charging the tubing with dry nitrogen prior to sealing. Evacuating moisture from the tubing before sealing. A coating of linseed oil.
Which of these materials is the most cathodic? Zinc. 2024 aluminum alloy. Stainless steel.
Of the following, when and/or where is galvanic corrosion is most likely to occur? When an electrolyte (water) covers the surface of an aluminum skin, seeps into the cracks between lap joints, and oxygen is excluded from the area. At the interface of a steel fastener and aluminum alloy inspection plate in the presence of an electrolyte. In an area of unprotected metal exposed to an atmosphere containing battery fumes, exhaust gases, or industrial contaminants.
One way of obtaining increased resistance to stress corrosion cracking is by relieving compressive stresses (via heat treatment) on the metal surface. creating compressive stresses (via shot peening) on the metal surface. producing nonuniform deformation while cold working during the manufacturing process.
(1) In the corrosion process, it is the cathodic area or dissimilar cathodic material that corrodes.
(2) In the Galvanic or Electro-Chemical Series for metals, the most anodic metals are those that will give up electrons most easily.
Regarding the above statements, only No. 1 is true. only No. 2 is true. both No. 1 and No. 2 are true.
Spilled mercury on aluminum greatly increases susceptibility to hydrogen embrittlement. may cause impaired corrosion resistance if left in prolonged contact. causes rapid and severe corrosion that is very difficult to control.
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