TO 1-1-700 - Robins Air Force Base

TO 1-1-700
CHAPTER 11
CORROSION REMOVAL
11.1 GENERAL.
This chapter covers procedures for corrosion removal and surface
treatment. When corrosion is detected, a specific and
immediate corrective action is required. Each type of corrosion
has its own peculiarities and requires special treatment.
Complete treatment involves a thorough inspection of all corroded
areas and evaluation of the corrosion damage (refer to
Chapter 9 of this manual), paint removal per TO 1-1-8, corrosion
removal per this chapter and TO 1-1-691, application of
chemical surface treatments per this chapter, sealing (refer to
Chapter 12 of this manual), and application/touch-up of protective
paint finishes per TO 1-1-8 and Chapter 7 of this manual.
11.1.1 Training. Personnel assigned to perform corrosion
removal corrective maintenance tasks shall be specially
trained in the use of chemical paint removers specified in TO
1-1-8; abrasive materials, powered and hand tools, depth and
area measurement of metal removed outlined in this chapter
and in TO 1-1-691; and determination of damage limits from
the applicable system specific maintenance manuals. Inadequate
training will lead to further damage of equipment and
poses a safety hazard to the individual.
11.1.2 Corrosion Risk. Parts including housings, covers,
supports, brackets, cabinets, and chassis are required for structural
support and mounting bases for electrical and electronic
components. Corrosion on these parts should be treated as
soon as possible to eliminate long term deterioration. Severe
corrosion usually results from coating failure caused by handling
or environmental exposure and subsequent attack of
exposed metal. The corrosion attack is caused by exposure to
elements such as moisture, corrosive deposits, and/or microbial
contamination.
11.1.3 Maintenance Level. Major repairs should be performed
at Depot Level maintenance. Preventive maintenance,
corrosion control, and touchup procedures should be accomplished
at the Intermediate Level maintenance and/or Organizational/Unit
Level maintenance.
11.2 CORRECTIVE ACTIONS.
Corrective maintenance depends on: the type of surface
involved (metallic or composite); the area of the damaged surface
(small corrosion spot or large corroded area); and the
degree of corrosion, as determined per Chapter 9 of this manual.
11.2.1 Exposure. Composite materials, such as fiberglass or
graphite/boron epoxy matrix structures, shall not be exposed
to chemical paint removers, but shall only be scuff sanded to
the primer coat.
11.2.2 Mechanical Procedures. Since composite materials
do not corrode, corrosion removal techniques are not applicable
and shall not be used. Corrosion shall always be removed
by the mildest effective technique. For mechanical procedures
specific to the various metal alloys, refer to Table 11-1 and
Table 11-2.
11.3 CORROSION REMOVAL METHODS.
Corrosion can be removed by either mechanical or chemical
methods. Certain factors must be considered prior to starting
any corrosion removal operation. The most important factor to
consider is that corrosion products must be removed completely
without causing additional damage to the structure during
the process. This can be accomplished by first removing
all corrosion visible through a 10X magnifying glass, then
removing an additional two mils (0.0020 inch) to ensure that
all deposits have been eliminated. Failure to remove all corrosion
allows the corrosion to continue even after affected surfaces
are refinished. Additional factors to consider are:
a. Before attempting to remove corrosion products, strip
the paint from the area to be worked and clean contaminants
from the surface. Surface contaminants and paint
interfere with corrosion removal procedures and make
the operation more difficult.
b. Protect adjacent components and parts from corrosion
residue and possible damage that could be caused by the
removal operation. Corrosion residue can cause additional
corrosion and damage the surface finish of the
surrounding area. An accidental slip of a corrosion
removal tool can quickly result in additional damage.
c. Prior to corrosion removal, determine the allowable limits
from the system specific equipment manuals and/or
technical orders. When removing corrosion from critical
equipment structure, take the following steps:
(1) If allowable metal removal or damage limits will not
be exceeded, remove corrosion completely. Metal
loss due to corrosion damage is cumulative. Metal
loss from prior corrosion removal operations and
corrosion removal from areas on the opposite side of
a part must be considered when assessing the degree
of corrosion damage.
11-1