(a)
Remove light corrosion by light hand sanding with abrasive paper
(Fig. 3).
(b)
As an alternative, remove light corrosion and stains with pumice
paste. Mix pumice powder with water to make a slurry paste. Apply
with a clean, soft cloth and rub gently. When paste is dried to a
white powder, wipe off with a clean, dry, soft cloth. Remove remain-ing corrosion and corrosion products with No. 600 grit wet or dry
abrasive paper and water.
(c) Remove heavy corrosion products by hand with any of the following
items:
1) Carbide-tipped scraper
2) Fine fluted rotary file
3) 400 grit aluminum oxide (alumina) abrasive paper
4) Stainless steel brush (with bristles no larger than 0.010 inch in
diameter)
After you use the stainless steel brush or file, polish the surface
with 400 grit alumina abrasive paper, and then with 600 grit
alumina abrasive paper.
CAUTION: HEAVY, CONTINUOUS RUBBING (SUCH AS WITH POWER-DRIVEN WIRE
BRUSHES) CAN MAKE ENOUGH HEAT TO CAUSE METALLURGICAL
CHANGES.
(d) Mechanically remove moderate or bad corrosion by stainless steel
wire brush (with bristles no larger than 0.010 inch in diameter),
grinding, or, only for filiform corrosion, abrasive blasting with
glass beads. Do not use glass bead abrasive blasting to remove other
types of corrosion that extend below the surface. Refer to par. 7.E.
for procedures. On nonclad anodized surfaces, be careful not to dam-age the anodized surface adjacent to the corrosion area.
Volume 1
20-40-00
Page 10
OCT 01/01
(e) Dry abrasive blasting with glass beads (par. 7.E.(3)) is approved to
remove only filiform corrosion from aluminum alloys. Do not use
glass bead abrasive blasting to remove other types of corrosion that
extend below the surface. Use air pressures of 40 to 80 psi. The
higher pressure removes corrosion more quickly.
(7)After you remove all corrosion that can be seen through a 10-power mag-nifying glass, remove 0.002-inch more material to be sure you removed
all the corrosion products.
(8)Blend repaired areas per par. 7.C.
(9)Clean the repaired area.
(10)Measure the depth of the blends per par. 7.D., to be sure that they are
within repair limits.
(ll)Treat the repaired area per 20-50-00.
C. Corrosion Removal -Chemical.
CAUTION: AVOID CHEMICAL REMOVAL AT TEMPERATURES ABOVE 100°F OR BELOW 40 F.
DO NOT USE ALKALINE TYPE CORROSION REMOVERS TO REMOVE CORROSION FROM
ALUMINUM ALLOYS.
WHEN APPLYING CORROSION REMOVAL SOLUTION, PARTICULAR CARE SHOULD BE
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