FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 6. Corrosion, Inspection, and Protection | 8. Aluminum and Aluminum Alloys | 6-136. Examples of Removing Corrosion From Aluminum and Aluminum Alloys
9/8/98
AC 43.13-1B
manufacture’s instructions before use. Type I
has a 1 year shelf life; therefore it shall not be
used after 1 year from the date of manufacture.
2 Type II Powdered concentrate
materials should be dissolved in the volume of
water specified on the kit. These materials
have an indefinite shelf life in the dry state.
Once mixed, they should be used within
90 days.
(b) Mix MIL-C-38334 in wood,
plastic, or plastic-lined containers only. Wear
acid-resistant gloves, protective mask and
protective clothing when working with this
acid compound. If acid contacts the skin or
eyes, flush immediately with water.
(c) Apply MIL-C-38334 solution by
flowing, mopping, sponging, brushing, or
wiping. When applying the solution to large
areas, begin the application at the lowest area
and work upward, applying the solution with a
circular motion to disturb the surface film and
ensure proper coverage. If pumping is re
quired, pumps, valves, and fittings should be
manufactured from 18-8 stainless steel or
plastic.
(d) Allow the solution to remain on
the surface for approximately 12 minutes and
then rinse away with clean tap water. For pit
ted or heavily-corroded areas the compound
will be more effective if applied warm
(140 °F) followed by vigorous agitation with a
non-metallic acid-resisting brush or aluminum
oxide abrasive nylon mat. Allow sufficient
dwell time, 12 to 15 minutes, before rinsing.
After each application examine the pits and/or
corroded area to determine if another applica
tion is required with a 4 to 10 power magnify
ing glass. (Select the power depending on the
distance available to make the inspection.)
Corrosion still on the area will appear as a
powdery crust slightly different in color than
the uncorroded base metal. Darkening of area
due to shadows and reaction from the acid re
mover should not be considered.
(e) Once the corrosion has been re
moved and the area well-rinsed with clean
water, a chromate conversion coating such as
MIL-C-81706 or MIL-C-5541 alodine 1200,
must be applied immediately thereafter.
e. Remove moderate to heavy corrosion
with one of the following.
CAUTION: When working with
MIL-C-38334, keep the solution away
from magnesium surfaces. The solu-
tion must be confined to the area be-
ing treated. All parts and assemblies
including cadmium-plated items and
hinges susceptible to damage from
acid should be masked and/or pro-
tected. Also mask all openings leading
to the primary structure that could
trap the solution and doors or other
openings that would allow the solution
(uncontrolled) to get into the aircraft
or equipment interior. It is a good
practice to keep a wet rag on hand at
all times, for removal of spills or
splashes.
(1) Powered Corrosion Removal.
(a) Where the problem is severe
enough to warrant the use of power tools, a
pneumatic drill motor driving either an alumi
num-oxide-impregnated nylon abrasive wheel,
flap brush or rubber grinding wheel may be
used with an abrasive value to approximately
120 grit, as needed. Corrosion-removal acces
sories, such as flap brushes or rotary files,
should be used on one type of metal only. For
example, a flap brush used to remove alumi
num should not be used to remove magnesium,
steel, etc. Pneumatic sanders may be used
with disk and paper acceptable for use on alu
minum.
Par 6-136
Page 6-27