(i)
If corrosion still exists, repeat immersion procedure above.
(j)
Dry thoroughly and fair or blend depressions from corrosion removal
per par. 7.C.
(k)
Determine depth of faired depression per par. 7.D., to ensure that
rework depth limits have not been exceeded.
(1)
Treat surface of reworked area per 20-50-00 immediately upon finish
of rework.
11.Corrosion Removal Procedure for Stainless Steel and Nickel-Chromium Alloys
A. General. Stainless steel and nickel-chromium alloys are used where corro-sion resistance is one of the major considerations in the design of the com-ponent or system. In most applications, these steels will have no other
surface protection except for matching color schemes of the surrounding
structure or dissimilar metal organic coatings. Stainless steel and nickel-
chromium steels, however, are not free from corrosion attack. Corrosion usu-ally appears as pits usually black in color. The existence of corrosion
products prevents a passivated environment at the stainless steel surfaces
and creates an active/passive corrosion cell (Ref 20-10-00). It is, there-fore, necessary that the corrosion removal is complete.
Volume 1
20-40-00
Page 18
OCT 01/01
CAUTION: ABRASIVE BLASTING OR GRINDING SHALL NOT BE USED ON THIN WALL TUBES OR
THIN WEBS LESS THAN 0.0625 INCH THICK.
B. Corrosion Removal -Mechanical. Use the same general procedures as for car-bon steel.
C. Corrosion Removal -Chemical. In severely corroded areas and where chemical
agents will not be trapped in cracks, crevices, lap joints, etc., the chem-ical removal methods described for carbon steel are applicable.
12.Corrosion Removal Procedure for Titanium Alloys
A. General. Titanium alloys are used in several locations in the airplane, par-ticularly in high-temperature areas and in areas where high-strength mem-bers are exposed to corrosive environment. Exposure of the titanium surface
to fire resistant hydraulic fluids such as BMS 3-11 causes hydrogen embrit-tlement subsequently leading to pitting of the surface. The alloy is gener-ally corrosion resistant. Corrosion, however, does appear as white or black
color oxides. Corrosion removal shall be accomplished per the following pro-cedures:
WARNING: SMALL CHIPS OR SILVERS OF A TITANIUM ALLOY, WHICH ARE THE RESULT
OF A MACHINING PROCESS OR PROCEDURE, CAN EASILY IGNITE. AN EXTREME
FIRE HAZARD MAY DEVELOP. EXTINGUISH SUCH FIRES WITH ABSOLUTELY DRY
TALC, CALCIUM CARBONATE, SAND OR GRAPHITE. DO NOT USE WATER, CAR-BON DIOXIDE, CARBON TETRACHLORIDE OR THE ORDINARY DRY CHEMICAL
FIRE EXTINGUISHER.
B. Corrosion Removal -Mechanical.
(1)If grease or soil is present, clean the area per par. 5.
(2)Hand polish with aluminum polish with a soft cloth until all traces of 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：757 防腐手册 CORROSION PREVENTION MANUAL 第二册 一般信息(31)
