D. Inspect structure for heat damage, soot, fire extinguishing material resi-
due and corrosion. Paint discoloration indicates temperature had exceeded
350°F (180°C)and requires structural analysis. Check for acid contamination
of structure, control cables and wire bundles using litmus paper. Products
of combustion or decomposed fire extinguishants may combine with moisture to
form corrosive chemicals. Flush structure with water as necessary to remove
contaminants and replace control cables, etc., as necessary.

E. Remove and replace structure damaged beyond repair.

NOTE: Use eddy current technique outlined in Nondestructive Test Manual to
determine any change in heat-treat of any suspect structure.

Volume 1

20-42-00
Page 1 OCT 01/01
CORROSION PREVENTION MANUAL
GENERAL INFORMATION CORROSION REMOVAL TECHNIQUES
PROCEDURE AFTER FIRE DAMAGE

WARNING: SOLVENTS CAN CAUSE SKIN IRRITATION. THE VAPOR MAY IRRITATE EYES AND
RESPIRATORY SYSTEM OR CAUSE HEADACHES, SLEEPINESS, OR FAINTING. USE
WITH ADEQUATE VENTILATION, FACE SHIELDS AND PROTECTIVE CLOTHING.
AVOID PROLONGED BREATHING OF VAPORS OR REPEATED CONTACT WITH SKIN.

F. Remove soot by washing affected areas with 1,1,1 -Trichloroethane, Aerof-luor 343, or Shopmaster RTU, nonflammable solvent-type cleaner. Pressure
gun application is suggested for flushing fay surface joints, such as
stringers to body skins. An absorbent cloth held beneath the area will catch
the contaminated solvent.

WARNING: SODIUM DICHROMATE IS TOXIC IF TAKEN INTERNALLY. USE PROTECTIVE CLOTH-ING, FACE MASK AND RESPIRATOR WHEN SPRAYING. CONTACT LOCAL AUTHORI-TIES FOR WASTE DISPOSAL REQUIREMENTS.

G. Inhibit corrosion that could be caused by residue from the dry powder fire
extinguisher by washing affected areas with a 10-percent-by-weight solution
of sodium dichromate. The dichromate solution acts as a mild corrosion
inhibitor. Thoroughly dry all treated surfaces before continuing with any
other treatment. Repeat rinse and inhibition treatment if any white residue
shows.

NOTE: Any remaining liquid dichromate solution will weep through seams and fas-tener holes during cabin pressurization and could subsequently discolor
the exterior paint finish. Forced hot air used to dry the area may be
necessary before further flight if humidity is high.

H. Inspect for remaining residue contaminants. Contaminants that remain behind
clips, brackets, nutplates, etc., may require removal of the item before
cleanup can be complete.

I. Remove corrosion using one of the methods described in 20-40-00.

J. Treat reworked surfaces per 20-50-00 and paint same as surrounding area (Ref
20-60-00).

K. Apply clear (Type I) BMS 3-23 corrosion inhibiting compound to cleaned-up
affected areas especially skin-to-stringer joints. Allow to air dry thor-oughly before reinstalling insulation blankets. It is important that the
　
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