205.159
Figure 4-15.—Filiform corrosion found under paint coating.
Q50.
What is usually the cause of dissimilar metal
corrosion?
Q51. What are some examples of internal stress
corrosion?
Q52.
What causes fatigue corrosion?
Q53.
What is the cause of fretting corrosion?
Q54. Filiform corrosion occurs on what types of
metals?
LOCATION OF CORROSION-
PRONE AREAS
LEARNING OBJECTIVE: Describe the areas
on an aircraft prone to corrosion.
This section discusses corrosion-prone areas
common to all aircraft. For specific aircraft, you
should refer to the periodic maintenance information
cards (PMICs) to locate corrosion-prone areas for that
aircraft. Figure 4-16 is an example of possible trouble
spots on jet engine aircraft.
Lavatories and galleys are likely trouble spots if
they are not kept clean. These areas include the deck
behind lavatories, sinks, and ranges where spilled food
and waste products may accumulate. Even when
contaminants are noncorrosive: they may attract and
hold moisture. This, in turn, causes corrosive attack.
Maintenance personnel should pay attention to bilge
areas located under galleys and lavatories and to
personnel relief and waste disposal vents or openings
on the aircraft exteriors. Human waste products can
corrode common aircraft metals.
Avionic Systems
The control of corrosion in avionic systems is not
unlike that in airframes. Procedures useful for
airframes apply to avionics, with appropriate
modifications. Avionics systems are more prone to
corrosion than aircraft because avionics have the
following characteristics:
Less durable protection systems,
Very small amounts of corrosion can make
equipment inoperative.
Dissimilar metals are often in electrical contact.
Stray currents are present that can cause
corrosion.
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