S 107-004
 (2)  Do the subsequent steps to remove small quantities of aluminum corrosion from the external surface of the airplane:
 NOTE: This procedure is optional.
____
 (a)  
Remove the corrosion with an approved airplane polish.

 (b)  
Use a solvent alkaline or emulsion cleaner to remove the remaining particles of airplane polish from the surface. Fully flush the surface with water (AMM 51-24-13/701).

 (c)  
Kelite Process K phosphoric acid type corrosion remover.

 NOTE: Before use, add 5 parts (by volume) of water to 1 part
____
 (by volume) of Kelite Process K.

 (d) Turco W.O. No. 1 phosphoric acid type corrosion remover.
 NOTE: Before use, add 6 parts (by volume) of water to 1 part
____
 (by volume) of Turco W.O. No. 1.

 (e)  
Apply phosphoric acid corrosion remover on the surface.

 (f)  
Fully flush all of the area, the prepared area and the adjacent areas, with water.

 NOTE: Make sure that you flush out all of the phosphoric acid
____ corrosion remover from the wheel well areas, the skin seams and all openings or holes on the surface.
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 S 107-029
 (3)  Do the subsequent steps to remove corrosion from magnesium:
 WARNING: SMALL PARTICLES OF MAGNESIUM CAN EASILY CAUSE IGNITION.
_______ USE DRY TALC, CALCIUM CARBONATE, SAND, OR GRAPHITE TO EXTINGUISH A MAGNESIUM FIRE. DO NOT USE WATER, CARBON DIOXIDE, CARBON TETRACHLORIDE, OR AN ORDINARY DRY CHEMICAL FIRE EXTINGUISHER TO EXTINGUISH A MAGNESIUM FIRE. INJURY OR DAMAGE CAN OCCUR IF INCORRECT PROCEDURES ARE USED TO EXTINGUISH A MAGNESIUM FIRE.
 CAUTION: MAKE SURE THAT ALL ADJACENT AREAS HAVE PROTECTION WHEN YOU
_______ REMOVE CORROSION. DAMAGE CAN OCCUR IF THE ADJACENT AREAS DO NOT HAVE PROTECTION DURING THE CORROSION REMOVAL.
 (a)  
Clean the corrosion with aluminum wool and a rigid bristled brush. If is is necessary, use aluminum oxide abrasive, 220-grit (minimum). Do not use silicone carbide abrasive.

 (b)  
Protect all material and parts not to be treated from contact with the corrosion removing solution or fumes.

 (c)  
Clean corrosion from pits with Dow 1 solution as follows:

 1)  Brush a generous quantity of Dow 1 solution mixed with 1-1/2 pounds of sodium dichromate and 1-1/2 pints of concentrated nitric acid per gallon.
 2)  Wipe dry, rinse with clean water, and wipe dry again.
 S 377-028
 (4)  Apply the protective finish as follows:
 (a)  Apply Dow 19 solution.
 1)  Prepare the solution in a clean glass or polyethylene container as follows:
 -add 9/10 gallons of water
 -
mix 1-1/3 ounces chromic acid

 -
mix 1 ounce calcium sulfate (powder)

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 2) Fill to the one gallon level with water. Stir for a minimum of 15 minutes and allow to settle. 3) Make sure the pH is from 1.2 to 1.6. Use sulfuric acid to lower the pH or use sodium hydroxide to increase the pH.
 CAUTION: SWAB THE SURFACE LIGHTLY AS SEVERE RUBBING OF THE WET
_______
 SURFACE WILL DAMAGE THE COATING.

 4)  Apply fresh solution until the surface becomes dark brown in color.
 CAUTION: HIGH PRESSURE WATER SPRAY, RUBBING ABRASION, AND HIGH
_______ PRESSURE AIR BLAST WILL DAMAGE THE FRESH COATING.
 5) Rinse with clean cold water. 6) Dry the solution with air at a maximum temperature of 180°F. 7) Make sure that the surface is free from uncoated areas,
 scratches, powder, and streaks. 8) Remove the powder by wiping the surface with a clean cloth. 9) Reapply the coating and touch up any uncoated areas.
　
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