757 防腐手册 CORROSION PREVENTION MANUAL 第二册 一般信息(32)

(3)Remove the polish with soft cloth.

(4)Treat reworked area per 20-50-00.

C. Corrosion Removal -Chemical. Because titanium is susceptible to hydrogen
embrittlement when exposed to acid solutions, chemical corrosion removers
are not permitted.

13.Corrosion Removal Procedures for Plated or Phosphated Surfaces

A. General. Metal parts are plated either to provide a smooth surface for wear
resistance or to provide a sacrificial metal to protect the base metal.
Phosphate treatments on metal surfaces provides a good adhesion surface for
organic finishes and provides good wear and corrosion resistance when used
with oil or corrosion preventive compounds. Cadmium plating corrosion will
appear as a dull gray product. Phosphate treated surfaces will appear as a
red-black part darker than common rust when corroded.

B. Corrosion Removal from Cadmium Plated Surfaces

(1)Protect adjacent areas from contaminants during corrosion removal.

Volume 1

20-40-00
Page 19 OCT 01/01
(2)If grease or soil is present, clean area per par. 5.

(3)If corrosion appears only on the plated surfaces, rework as follows:

(a)
Remove corrosion products by rubbing lightly with stainless steel
wool. Limit rework area to a minimum so that plating material in
adjacent area is preserved.

(b)
Apply chromic acid solution to the corroded area and allow to remain
on surface for 30 to 60 seconds. The solution strength shall be 4
ounces of chromium trioxide to 1 U.S. gallon of water.

(c)
Rinse with clean water and air dry.

(4)If corrosion has penetrated to the base metal, rework as follows:

(a)
Determine from SRM if part shall be reworked or replaced.

(b)
If part can be reworked, identify the base metal and remove corro-sion per applicable procedures.

(5)Treat rework surface per 20-50-00.

C. Corrosion Removal from Plated Surfaces (Except Cadmium Plated Surfaces)

(1)Protect adjacent areas from contaminants during corrosion removal.

(2)If grease or soil is present, clean area per par. 5.

(3)Remove heavy corrosion by mechanical method per par. 7.E.

(4)Remove remaining corrosion using phosphoric acid base rust remover
(mixed on a 1:1 ratio). Allow acid solution to remain only long enough
to remove the corrosion.

(5)Thoroughly rinse the acid from the surface with clean water.

(6)Air dry and treat the reworked surface per 20-50-00.

D. Corrosion Removal from Phosphated Surfaces

(1)Phosphated cadmium surfaces shall be treated per procedures for cadmium
plated surfaces.

(2)Phosphated ferrous alloys shall be treated per procedures for carbon
steel.

Volume 1

20-40-00