TO 1-1-700 - Robins Air Force Base

TO 1-1-700
(2) If allowable damage limits will be exceeded, repair
the damaged area or replace parts per procedures in
system specific equipment repair manuals/technical
orders. Coordinate any repair or part replacement not
covered in these manuals/technical orders with the
equipment SPM.
11.3.1 Mechanical Methods. There are various mechanical
methods for removing corrosion from metal surfaces. The
method used and the types of tools and equipment selected for
the removal operation depend on the type of metal involved,
the location and accessibility of the corroded area, the degree
of damage, and the type of corrosion involved. It is important
that the removal method, tools, and equipment selected be
compatible with the metal surface. Compatibility involves two
considerations: the mechanical effect of the equipment and
tools on the surface, and the compatibility of metallic particles
worn off the removal equipment and tools which might
become embedded in the metal surface.
Corrosion removal accessories/tools, such as flap
brushes or rotary files, shall be used on one type of
metal only. For example, a flap brush used to remove
corrosion from aluminum alloys shall not be used to
remove corrosion from magnesium alloys or steel also.
11.3.1.1 Mechanical Compatibility. Mechanical compatibility
refers to the selection of the right tools and equipment to
prevent additional damage caused by the removal process.
Often it is necessary to select a series of removal techniques
involving the use of different grades or classes of equipment
and material to effectively remove the corrosion products. The
initial use of a rapid and coarse removal method followed by a
slower and finer removal method produces a smooth metal
surface finish (e.g., using a vacuum blaster first followed by
using a fine abrasive cloth or paper to finish the job).
11.3.1.2 Material Compatibility. Material compatibility
refers to using a medium for brushing, abrading, blasting, etc.,
which will not cause additional corrosion. Material compatibilities
are assured by using like metals during corrosion
removal operations (e.g., regular carbon steel wool shall never
be used to remove corrosion from aluminum alloys as it will
embed in the aluminum alloy surface and cause galvanic corrosion).
11.4 NON-POWERED TOOLS AND MATERIALS.
Below is a list of several non-powered tools and materials
commonly used in the process of corrosion removal. For a
complete list of tools and materials procurement information
refer to Appendixes A and B in TO 1-1-691.
11.4.1 Abrasive Mats. Abrasive mats are made from a
nylon mesh material impregnated with various grades of aluminum
oxide. Abrasive mats are available in 9 x 11 inch
sheets under A-A-58054, Type I, Class 1, Grade A - Very Fine
(280-400 grit), Grade B - Fine (180 grit), and Grade C -
Medium (100-150 grit). These mats are used by hand to
remove small areas of corrosion and/or paint where the use of
powered tools would be impractical or prevented by the shape
or accessibility of the area. Use Table 11-2 as a guide to relate
abrasive mat materials to coated abrasive paper and/or cloth
grit particle sizes.
11.4.2 Abrasive Cloth. Abrasive cloths with bonded aluminum
oxide grit per A-A-1048 and silicon carbide grit per A-A-
1200 are used for dry sanding of light to moderate corrosion
products. They are available in 9 x 11 inch sheets and 2 or 3
inch wide x 150 foot long rolls in 240 grit (fine) and 320 grit
(very fine) grades.
11.4.3 Abrasive Paper. Heavy paper with silicon carbide
grit bonded to it per A-A-1047 is used for either wet or dry
sanding to remove light to moderate corrosion. It is available
in 9 x 11 inch sheets in 240 grit (Fine) and 320 grit (Very Fine)
grades. Silicon carbide is usually more effective than aluminum
oxide on harder metals such as low carbon and corrosion
resistant steel alloys. Other abrasive paper and cloth with
bonded emery or flint are available, but they suffer from poor
efficiency and short working life.
11.4.4 Wire Brushes. Wire brushes are available with carbon
steel, stainless steel (CRES), aluminum, and brass bristles
and are used to remove heavy corrosion deposits and flaking
paint that are not tightly bonded to the metal surface. Densely
set, short, stiff bristles are most effective for rapid corrosion
removal. The metallic bristles must be compatible with the
metal surface being treated to prevent galvanic corrosion with
stainless steel (CRES) being considered neutral and usable on
all metals. Do not use brushes with a bristle wire gauge or
diameter above 10.0 mils (0.010 inch), as severe gouging of
the surface may occur and lead to stress risers that can cause
stress and fatigue cracking. Remove the corrosion with a linear
motion; do not cross-hatch as this will unnecessarily damage
the surrounding surface area. After wire brushing, the
surface areas must be polished with fine abrasive paper to
remove and/or smooth out any gouges and scratches.
11.4.5 Scrapers. Scrapers are used primarily for the initial
removal of heavy corrosion deposits such as flaking rust and
exfoliation blisters, and are particularly effective in corners
and crevices that cannot be reached with other equipment.
11-2