B. Referenced Procedures
(1) Alodine Coating (Ref. 51-21-41)
C. Prepare to Polish the Surface
(1) Use the “Clean The External Surfaces Of The Airplane” procedure to clean the surfaces you will polish.
D. Polish the Surface
WARNING: DO NOT POLISH THE STATIC PORTS. IF POLISHING MATERIAL ENTERS THE STATIC PORTS, IT MAY CAUSE LARGE ERRORS IN AIRSPEED-SENSING AND ALTITUDE-SENSING SIGNALS, WHICH MAY LEAD TO LOSS OF SAFE FLIGHT.
(1) PROCEDURE I - Polish the surface to repair light stains or to make the surface bright.
(a)
Use the wiper to remove the outer layer of protection as necessary.
(b)
Manually or mechanically polish the surface as follows: 1) ALTERNATIVE I - Manually polish the surface. a) Apply AS-0410 fine polishing paste or Turco 1495-X polish to the BMS 15-
5D Class A wiper. b) Rub the damaged area of the surface with the wiper.
NOTE: Rub in the direction of the grain of the metal until you get the necessary finish.
2) ALTERNATIVE II - Mechanically polish the surface. a) Apply AS-0410 fine polishing paste or Turco 1495-X polish to the BMS 15-5D Class A wiper. b) Polish the damaged area of the surface with the orbital air-driven sander/polisher.
(c)
Remove the remaining polish material with solvent wipers.
(d)
If necessary, use ALTERNATIVE I or II to polish the surface again.
NOTE: If the polished area is too bright, rub the area with an ultra fine Scotch-Brite pad. Remove the dried polish with solvent and wipers.
(e)
Rub the area around the polished area to get a constant finish.
(f)
Do the “Clean the External Surfaces of the Airplane” procedure in the polished area.
(g)
Put some water on the surface, and make sure the water becomes drops.
(h)
If the surface was conversion coated before it was polished, apply Alodine 1000 with a swab, or sponge (Ref. 51-21-41).
NOTE: Always wipe in the direction of the grain of the metal.
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(2) PROCEDURE II - Polish the surface to remove heavy stains or scratches that do not penetrate the clad aluminum.
(a) Use these steps to find if the scratch penetrated the clad aluminum:
1) Apply BMS 3-2 cleaning solvent to a wiper.
2) Use the wiper to clean the area around the scratch.
3) Dry the surface.
4) Apply masking tape around the scratch.
NOTE: Make sure there is no more than 1/32 inch of bare metal around the scratch.
5) Prepare the clad penetrating solution as follows:
a) Mix 200 grams of Potassium Nitrate (KN03) and 100 grams of Sodium Hydroxide (NaOH) with sufficient water to make one liter of clad penetrating solution.
6) Apply one drop of clad penetrating solution with the point of a toothpick to the deepest part of the scratch.
CAUTION: MAKE SURE YOU PUT THE CLAD PENETRATING SOLUTION ONLY ON THE SCRATCH. THE SOLUTION WILL CAUSE DAMAGE TO THE SURFACE WHERE IT IS APPLIED.
NOTE: Use the minimum quantity of the clad penetrating solution necessary to flow to the bottom of the scratch.
7) If there is a positive reaction, immediately flush the scratch with water. Do not let the clad penetrating solution stay on the scratch for more than 3 minutes.
NOTE: If the bottom of the scratch becomes black, then the scratch penetrated the clad to the base metal.
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8) Prepare the nitric acid solution as follows:
a) Mix one volume of nitric acid (40 or 42° Be) with two to three volumes of
water.
9) Apply one drop of the nitric acid solution to the scratch.
10) Let the nitric acid solution stay on the scratch for 1/2 to 1 minute.
11) Flush the scratch with clean water.
12) Apply Alodine 1000 to the scratch with a swab, cloth, or sponge (Ref. 51-21-41).
(b)
If the scratch penetrated the clad aluminum, do PROCEDURE III.
(c)
Use the “Clean and External Surfaces of the Airplane” procedure to clean around the scratch.
(d)
If the surface is badly scratched, rub it with fine or ultrafine Scotch-Brite pads to make it smoother.
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