FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 6. Corrosion, Inspection, and Protection | 12. Plated Parts | 6-194. Cadmium and Zinc-plated Parts
9/8/98
SECTION 12. PLATED PARTS
AC 43.13-1B
6-193. CHROMIUM AND NICKEL-
PLATED PARTS. Nickel and chromium
platings are used extensively as protective and
wear-resistant coatings over high-strength steel
parts (landing gear journals, shock strut pis
tons, etc.). Chromium and nickel plate provide
protection by forming a somewhat impervious
physical coat over the underlying base metal.
When breaks occur in the surface, the protec
tion is destroyed.
a. The amount of reworking that can be
performed on chromium and nickel-plated
components is limited.
b. The rework should consist of light
buffing to remove corrosion products and pro
duce the required smoothness. The buffing
should not take the plating below the mini
mum allowable thickness.
c. Whenever a chromium or nickel-plated
component requires buffing, coat the area with
a corrosion-preventive compound, if possible.
d. When buffing exceeds the minimum
thickness of the plating, or the base metal has
sustained corrosive attack, the component
should be removed and replaced.
e. The removed component can be re
stored to serviceable condition by having the
old plating completely stripped and replated in
accordance with acceptable methods and
specifications.
6-194. CADMIUM AND ZINC-PLATED
PARTS. Cadmium plating is used extensively
in aircraft construction as a protective finish
over both steel and copper alloys. Protection
is provided by a sacrificial process in which
the cadmium is attacked rather than the un
derlying base material. Properly functioning
cadmium surface coatings may show mottling,
ranging from white to brown to black spots on
their surfaces. These show the sacrificial pro
tection being offered by the cadmium coat, and
under no condition should such spotting be
removed merely for appearance sake. In fact,
cadmium will continue to protect even when
actual breaks in the coating develop and bare
steel or exposed copper surfaces appear.
a. When the breakdown of the cad-
mium plating occurs and the initial appear
ance of corrosion products on the base metal
develops, some mechanical cleaning of the
area may be necessary but shall be limited to
removal of the corrosion products from the
underlying base material.
b. Under no condition should such a
coating be cleaned with a wire brush. If pro
tection is needed, a touch-up with primer or a
temporary preservative coating should be ap
plied. Restoration of the plate coating cannot
be done in the field.
c. Zinc coatings offer protection in an
identical manner to cadmium, and the correc
tive treatment for failure is generally the same
as for cadmium-plated parts. However, the
amount of zinc on aircraft structures is very
limited and usually does not present a mainte
nance problem.
6-195.6-205. [RESERVED.]
Par 6-193
Page 6-39 (and 6-40)