Aircraft Cleaning and Corrosion Control Flashcards

Comprehensive practice questions covering aircraft cleaning, corrosion identification and removal, and finishing processes based on the lecture notes.

What can happen to metal structures when nonapproved cleaning compounds are used on an aircraft?

It can result in hydrogen embrittlement.

According to the transcript, how should magnesium engine parts be cleaned?

Wash with a commercial solvent, decarbonize, and scrape or grit blast.

If registration numbers have a letter height of $12 \text{ inches}$, what is the minimum space required for the mark $N1683C$ (using the provided width/spacing ratios)?

$$52 \text{ inches}$$

How can an anodized surface coating that is damaged in service be partially restored?

By chemical surface treatment.

What is the specific purpose of conducting a water break test on metal?

To make certain that a bare metal surface is thoroughly clean.

Which solvent is recommended for wiping down cleaned surfaces immediately before painting?

Aliphatic naptha

How should nickel-cadmium battery cases and drain surfaces affected by electrolyte be neutralized?

With a solution of boric acid.

Which procedures and equipment are acceptable for using chemical cleaning agents on an aircraft?

Cotton fiber wiping cloths when using a flammable agent and atomizing spray equipment.

What solvent is specifically mentioned for cleaning rubber and acrylics?

Aliphatic naphtha

Why do fayed surfaces cause concern during the chemical cleaning process?

There is a danger of entrapping corrosive materials.

What effect do caustic cleaning products have on aluminum structures?

They produce corrosion.

Under what physical conditions is fretting corrosion most likely to occurring?

When two surfaces fit tightly together but can move relative to one another.

What is the fundamental cause of rust or corrosion occurring in most metals?

A tendency for the metals to return to their natural state.

What are the two desired effects of applying Alodine(r) (Bonderite(r)) to aluminum alloy?

A slightly rough surface and increased corrosion resistance.

Which of the following is NOT a requirement for corrosion to occur: an electrolyte, a cathode, an anode, or a passive oxide film?

The presence of a passive oxide film.

What is the term for the lifting or flaking of metal surface due to delamination of grain boundaries?

Exfoliation

What is the nonelectrolytic chemical treatment used to increase aluminum alloy corrosion resistance and paint-bonding?

Alodizing

What materials are acceptable for cleaning anodized surfaces?

Aluminum wool and fiber bristle brushes.

Can intergranular corrosion in aluminum alloy parts always be detected by surface indications?

No, it cannot always be detected by surface indications.

Which type of corrosion in aluminum structures may not be detectable even by careful visual inspection of the surface?

Intergranular corrosion

What material may be used to remove corrosion specifically from highly stressed steel surfaces?

Fine-grit aluminum oxide

What is considered a primary cause of intergranular corrosion?

Improper heat treatment.

What type of tool should be used to remove corrosion from magnesium parts?

A stiff, nonmetallic brush.

When preparing engines for storage, why must the crankshaft not be rotated after the corrosion preventive mixture is in the cylinders?

Because the seal of the corrosion preventive mixture will be broken.

What is the acceptable first step when cleaning a transparent plastic surface to prevent scratching?

Flush the surface with clean water.

What is the procedure for cleaning a tire if oil or grease comes in contact with it?

Wipe it with a dry cloth, wash down and rinse with soap and water.

When is galvanic corrosion likely to be at its most rapid and severe?

When the surface area of the anodic metal is smaller than the surface area of the cathodic metal.

What is the cause of corrosion resulting from galvanic action?

Contact between two unlike metals.

Between magnesium and stainless steel, which material is the most anodic?

Magnesium

What is the best way to protect the interior surface of sealed structural steel tubing from corrosion?

Apply a coating of linseed oil.

Between magnesium and stainless steel, which material is the most cathodic?

Stainless steel

At what specific interface is galvanic corrosion most likely to occur?

At the interface of a steel fastener and aluminum alloy inspection plate in the presence of an electrolyte.

How can an aviation mechanic increase a metal surface's resistance to stress corrosion cracking?

By creating compressive stresses via shot peening on the metal surface.

According to the Galvanic or Electro-Chemical Series, which metals give up electrons most easily?

The most anodic metals.

What is the result of spilling mercury on aluminum?

It causes rapid and severe corrosion that is very difficult to control.

What happens if masking tape is left on an aircraft finish for several days or exposed to heat?

The tape will likely cure to the finish and be very difficult to remove.

What is the purpose of using a retarder in aircraft finishes?

To slow the drying time and to prevent blush.

Which coating component includes phosphoric acid during the application process?

Wash primer

Which topcoat finish is identified as the most durable and chemical resistant?

Polyurethane

What is the primary reason for including aluminum pigment in dope?

To reflect ultraviolet from the fabric.

What is a correct use for acetone in aircraft maintenance?

To remove grease from fabric.

What hazard is associated with sanding fabric-covered surfaces during finishing?

Static electricity buildup.

If unhydrated wash primer is applied to unpainted aluminum in low humidity and topcoated $30$ to $40$ minutes later, what occurs?

Corrosion occurs.

What is the function and application method of fungicidal dopes?

They are used as the first coat to prevent fabric rotting and are applied thin enough to saturate the fabric.

What should an aviation mechanic avoid doing before applying a protective coating to unpainted clean aluminum?

Touching the surface with bare hands.

If hydrated wash primer is applied to unpainted aluminum in low humidity and topcoated $30$ to $40$ minutes later, what occurs?

A glossy, blush-free finish.

What is the most common cause of runs and sags in an aircraft finish?

Applying too much material in one coat.

Which defect in aircraft finishes is caused by drafts, adverse humidity, or sudden temperature changes?

Blushing

What is true regarding the compatibility of old wash primer coats and epoxy finishes?

Old wash primer coats may be overcoated directly with epoxy finishes.