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
AC 43.13-1B
9/8/98
6-135. CORROSION REMOVAL
AROUND COUNTERSUNK FASTENERS
IN ALUMINUM ALLOY. Intergranular cor
rosion in aluminum alloys often originates at
countersunk areas where steel fasteners are
used.
a. When corrosion is found around a
fixed fastener head, the fastener must be re
moved to ensure corrosion removal. All cor
rosion must be removed to prevent further cor
rosion and loss of structural strength. To re
duce the recurrence of corrosion, the panel
should receive a chemical conversion coating,
be primed, and have the fasteners installed wet
with sealant.
b. Each time removable steel fasteners
are removed from access panels, they should
be inspected for condition of the plating. If
mechanical or plating damage is evident, re
place the fastener. One of the following fas
tener installation methods should be used:
(1) Brush a corrosion-preventive com
pound on the substructure around and in the
fastener hole, start the fastener, apply a bead of
sealant to the fastener countersink, set and
torque the fastener within the working time of
the sealant (this is the preferred method).
(2) Apply the corrosion preventive
compound to the substructure and fastener, set
and torque the fastener.
(3) Apply a coating of primer to the
fastener, and while wet with primer, set and
torque the fastener.
6-136. EXAMPLES OF REMOVING
CORROSION FROM ALUMINUM AND
ALUMINUM ALLOYS.
a. Positively identify the metal as alumi
num.
b. Clean the area to be reworked. Strip
paint if required.
c. Determine extent of corrosion damage.
d. Remove light to moderate corrosion
with one of the following.
(1) Non-Powered Corrosion Removal.
(a) The removal of corrosion prod
ucts by hand can be accomplished by use of
aluminum grit and silicon carbide abrasive,
such as non-woven, non-metallic, abrasive mat
(Spec. MIL-A-9962), abrasive cloth, and pa
per. Aluminum wool, fiber bristle brushes, and
pumice powder are also acceptable methods.
(b) Stainless steel brush (Spec.
H-B-178, type III, class 2) may be used as long
as the bristles do not exceed 0.010 inch in di
ameter. After use of this brush the surface
should be polished with 60 grit aluminum ox
ide abrasive paper, then with 400 grit alumi
num oxide paper. Care should be exercised in
any cleaning process to avoid breaking the
protective film.
(c) Steel wool, emery cloth, steel
wire brushes (except stainless steel brush)
copper alloy brushes, rotary wire brushes, or
severe abrasive materials should not be used
on any aluminum surface.
(2) Chemical Corrosion Removal.
(a) The corrosion removal compound
aluminum pretreatment MIL-C-38334, an acid
material, may be used to remove corrosion
products from aluminum alloy materials or
items (e.g., skins, stringer, ribs in wings, tub
ing, or ducts). MIL-C-38334 is available in
two types:
1 Type I Liquid concentrate mate
rials should be diluted in accordance with the
Page 6-26
Par 6-135