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Chapter 1. General
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1. BACKGROUND.
Corrosion is the electrochemical deterioration of a metal because of
its chemical reaction with the surrounding environment. While new and better
materials are continuously being developed, this progress is offset, in
part, by a more aggressive operational environment. This problem is compounded
by the fact that corrosion is a complex phenomenon. It can take many different
forms and the resistance of aircraft materials to corrosion can drastically
change with only a small environmental change.
2. CATASTROPHIC CORROSION EVENTS.
Corrosion is most often thought of as a slow process of material deterioration,
taking place over a significant period of time (examples being general
corrosion, pitting, exfoliation, etc.). Other forms of corrosion degradation
can occur very quickly, in days or even hours, with catastrophic results.
These forms (such as stress corrosion cracking, environmental embrittlement,
and corrosion fatigue) depend on both the chemical and mechanical aspects
of the environment and can cause catastrophic structural failure without
warning. |
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3. CORROSION CONTROL PROGRAM.
a. The possibility of an inflight mishap or excessive down time for
structural repairs necessitates an active corrosion prevention and control
program. The type and aggressiveness of the corrosion prevention and control
program depend on the operational environment of the aircraft. Aircraft
exposed to salt air, heavy atmospheric industrial pollution, and/or over
water operations will require a more stringent corrosion prevention and
control program than an aircraft that is operated in a dry environment.
b. In order to prevent corrosion, a constant cycle of cleaning, inspection,
operational preservation, and lubrication must be followed. Prompt detection
and removal of corrosion will limit the extent of damage to aircraft and
aircraft components. The basic philosophy of a corrosion prevention and
control program should consist of the following:
(1) Adequately trained personnel in the recognition of corrosion including
conditions, detection and identification, cleaning, treating, and preservation;
(2) Thorough knowledge of corrosion identification techniques;
(3) Proper emphasis on the concept of all hands responsibility for
corrosion control;
(4) Inspection for corrosion on a scheduled basis;
(5) Aircraft washing at regularly scheduled intervals;
(6) Routine cleaning or wipe down of all exposed unpainted surfaces;
(7) Keeping drain holes and passages open and functional;
(8) Inspection, removal, and reapplication of preservation compounds
on a scheduled basis;
(9) Early detection and repair of damaged protective coatings.
(10) Thorough cleaning, lubrication, and preservation at prescribed
intervals;
(11) Prompt corrosion treatment after detection;
(12) Accurate record keeping and reporting of material or design deficiencies;
and
(13) Use of appropriate materials, equipment, and technical publications.
4 - 199 RESERVED
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