1. General

A.  The data contained in this subject is general. For system and model specific
preventive maintenance procedures, refer to Volume 2.

2.  Airplane Washing

A.  Washing helps decrease corrosion as well as maintain the appearance of the
airplane. Procedures for airplane washing are in Chapter 12 of the Mainte-nance Manual.

B.  Washing removes corrosive deposits that collect on airplane surfaces. Dirt
collects moisture that then causes corrosion. But other factors are impor-tant in a washing program:

(1)
Washing and in particular high-pressure water or steam can get moisture
into areas not usually contaminated.

(2)
The detergents used for washing can cause corrosion if they are not
fully rinsed off. Rinsing can be a problem if high-pressure hoses pushed
the washing solution into small cavities.

(3)
Any washing solution that removes unwanted grease and oil will also
remove the grease and oil that must stay for lubrication. Lubrication
again after airplane washing will then be necessary.

(4)  
Frequent washing will in time remove corrosion inhibiting compounds,

such as BMS 3-23,3-26,3-29 or 3-35. The time is a function of the fre-quency of washing and the strength of the detergent.

(5)
Too much polishing of unpainted aluminum surfaces can wear away the clad
surfaces.

C.  The washing frequency must agree with the operating environment and external
appearance of the airplane. As a guide these frequencies are recommended:

(1)  
Mild Zones--90 days

(2)  
Moderate Zones--45 days

(3)  
Severe Zones--15 days

D.  Polishes can be used on unpainted surfaces but possibly only once every 18
months or 2 years.

3.  Protective Finish

A.  Maintenance of the surface finish is important to prevent corrosion prob-lems. Damage to paint or other surface coatings should be repaired at the
earliest convenient opportunity. Until you can repair the finish, use a cor-rosion inhibitor to minimize the risk of corrosion.

B.  Where damage to the finish is not confined to the paint, and on surfaces
without paint, treat the metal per SOPM 20-50-00 before you apply the paint.

C.  Examples of finish systems are shown in Fig. 1. Refer to Chapter 51 of the
Maintenance Manual for details of how to remove and apply finishes.

Volume 1

20-60-00
Page 1 OCT 01/02
CORROSION PREVENTION MANUAL
GENERAL INFORMATION
STANDARD PREVENTIVE MAINTENANCE PROCEDURES

4.  Corrosion Inhibitors

A.  Corrosion inhibitors are used with finish systems and to prevent or stop
corrosion when the finish system is damaged. Many can get into small cavi-ties to push out water. Thus, they can go in between faying surfaces or
　
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