(4)Remove all surface defects. Use the correct abrasive to get the neces-sary surface finish.
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D. Repair Depth Measurement. After you remove the corrosion and blend out the
area., make depth measurements to be sure that the blend is not deeper than
the repair limit. A dial depth gage (Fig.2) or impression materials can be
used to find the depth (Fig. 2).
E. Corrosion Removal -Mechanical. The mechanical corrosion removal procedure
is recommended for most cases of corrosion damage. Some examples of this
procedure are: hand sanding with abrasive paper or metal wool, power sanding
with abrasive mats, grinding wheels, wire brushes or rubber mats, carbide
tipped scrapers and abrasive blasting. For general procedures, refer to the
steps below. For details for the different metals, refer to par. 8 and on.
(1)Wire Brushing. Wire brushing is a mechanical abrasive operation unusu-ally done with a hand wire brush or a wire brush mounted on a motor-
driven wheel. By using brushes of various lengths and gages of wire, a
wide range of abrasive action is possible. Wire brushing is used to
remove heavy corrosion and paint or dirt, especially where chemical
treatment is impractical. A typical wire brushing procedure follows:
(a)
Protect adjacent components from scale, chips, corrosion products
and chemical agents.
(b)
If you find grease or dirt, clean the area per par. 5.
(c)
Remove any loose corrosion with a hand scraper.
WARNING: THE USE OF GOGGLES OR FACE SHIELD IS MANDATORY WHEN USING MOTOR-DRIVEN WIRE BRUSHES.
(d) Wire brush area to a firm metal substrate.
(2)Grinding. Grinding is a method of removing heavy corrosion by means of
motorized grinding wheels or abrasive belts. Part of the base metal is
ground away with the corrosion. A typical grinding procedure follows:
(a)
Protect adjacent components from scale, chips, corrosion products
and chemical agents.
(b)
If you find grease or dirt, clean the area per par. 5.
WARNING: THE USE OF GOGGLES OR FACE SHIELD IS MANDATORY WHEN USING MOTOR-DRIVEN GRINDERS.
CAUTION: MOTORIZED GRINDING, IF NOT CAREFULLY MONITORED, CAN REMOVE MORE
MATERIAL THAN NECESSARY. THE USE OF OTHER REWORK METHODS IS PRE-FERRED.
(c) Remove paint and corrosion by grinding until a firm corrosion free
surface is reached. Continue grinding to remove coarse irregulari-ties. Use find abrasive paper to polish the surface to the desired
finish.
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(3)Glass Bead Abrasive Blasting. Abrasive blasting is used to clean or fin-ish metals and other materials. It hits the surface with a stream of
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