CORROSION PREVENTION CONTROL MANUAL
CORROSION PREVENTION AFTER FIRE — CORROSION PREVENTION
1. Procedure After Fire Damage
A. General
Service experience has indicated that corrosion problems can occur if the fire damaged areas are not
immediately cleaned. Sooty deposits resulting from burning organic materials and the residue from
the use of dry powder fire extinguishers are sources of contaminants that can initiate corrosion on
metal components and structures.
The dry powder type fire extinguishers are considered very effective in combating aircraft fires. The
powder from extinguishers of this type is decomposed by heat to form carbon dioxide which smothers
the fire. The residual deposit, however, is hygroscopic (absorbs moisture) and forms sodium
hydroxide upon absorbing moisture from the air or upon being mixed with water from aircraft flushing.
Sodium hydroxide is alkaline and can cause corrosion damage to aluminum structure, electrical
components, etc. Use large quantities of water for flushing in every compartment, crevice, corner and
behind electrical panels to eliminate all traces of this rather insoluble white powder.
Halogen type (e.g., Halon or BCF) fire extinguishers normally leave no chemical residue to corrode
parts or surfaces. However, when subjected to flame or hot surfaces, halogenated agents can
decompose to produce small amounts of acids.
The complete removal of residual moisture before any reassembly (to prevent entrapment of fluids)
is equally important.
B. Preventive Maintenance
(1) Remove fire damaged interiors to expose structures. This includes interior trim, seats,
passenger service units, linings, insulation, galleys, etc. Removal of tubing, cables, electrical
wiring, etc., is not necessary if they were not affected by the fire.
(2) Screen or mask off unaffected areas.
(3) Open all drains, hatches and doors for drainage and ventilation. Use low pressure compressed
air to blow dry all hidden recesses.
(4) Inspect structure for heat damage, soot, fire extinguishing material residue and corrosion.
Discolored paint indicates that temperatures have exceeded 350°F (180°C) and that structural
analysis is required. Using litmus paper, check for acid or caustic contamination on structure,
control cables and wire bundles. Combustion products or decomposed fire extinguishing
chemicals can combine with moisture to form corrosive chemicals. Flush structure with water
(as necessary) to remove contaminants and if required, replace control cables, etc.
NOTE: Eddy current NDT techniques may be required to determine any change in heat treat
condition (i.e., strength) of any suspect structure. Contact Gulfstream Customer
Support for assistance.
(5) Remove and replace structures obviously damaged beyond repair.
WARNING: 1,1,1 TRICHLOROETHANE CAN CAUSE SKIN IRRITATION. THE VAPOR CAN
IRRITATE THE EYES AND RESPIRATORY SYSTEM AND / OR CAUSE
HEADACHES, SLEEPINESS OR FAINTING. USE WITH ADEQUATE
VENTILATION, FACE SHIELDS AND PROTECTIVE CLOTHING. AVOID
PROLONGED BREATHING OF VAPORS OR REPEATED CONTACT WITH
THE SKIN.
(6) Remove soot by washing affected areas with Trichloroethane. Pressure gun application is
suggested for flushing faying surface joints, such as stringers to body skins. An absorbent cloth
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held beneath the area being washed will help to catch the contaminated solvent.
WARNING: SODIUM DICHROMATE IS TOXIC IF TAKEN INTERNALLY. USE PROTECTIVE
CLOTHING, FACE MASK AND RESPIRATOR WHEN SPRAYING. CONTACT
LOCAL AUTHORITIES FOR WASTE DISPOSAL REQUIREMENTS.
(7) Wash affected areas with a 10% (by weight) solution of sodium dichromate to inhibit corrosion
that could be caused by residue from the dry powder fire extinguisher. The sodium dichromate
solution acts as a mild corrosion inhibitor. Thoroughly dry all treated surfaces before continuing
with any other treatment. If any white residue appears, rinse and repeat the treatment by again
washing with sodium dichromate.
NOTE: Any remaining sodium dichromate solution could weep through seams and fastener
holes during cabin pressurization and subsequently discolor the aircraft exterior paint
finish. If humidity is high, forced hot air may be used to dry the area before further
flight.
(8) Inspect for remaining residue contaminants. Contaminants which remain behind clips, brackets,
nut plates, etc., may require removal of these components before cleanup is complete.
(9) Remove corrosion using one of methods described in Corrosion Removal Techniques,
20-50-01, Corrosion Prevention.
(10) Treat reworked surfaces as described in Standard Surface Treatment Methods, 20-50-05,
Corrosion Prevention and paint the same as the surrounding area in accordance with Standard
Preventive Maintenance Methods, 20-53-00, Corrosion Prevention. Ensure that paints and
sealants are adequately cured before applying any corrosion inhibiting compounds.
(11) Apply Type II corrosion inhibiting compound as described in Standard Preventive Maintenance
Methods, 20-53-00, Corrosion Prevention (LPS-3 preferred) to the cleaned, affected areas
(especially skin to stringer joints). Allow to air dry thoroughly before installing insulation
blankets. It is important that the affected area be covered with a continuous film of the inhibiter.
Use a rag or brush to spread the puddles. A thin, even application is all that is required to
provide corrosion protection and to prevent moisture from placing the sodium dichromate into
solution again and possibly staining the aircraft exterior surfaces.
(12) Replace all interior items and restore aircraft to a serviceable condition.
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