TO 35-1-3 - Robins Air Force Base

TO 35-1-3
1.6.7.3 When dry, some microorganisms can survive in spore
form for long periods and can become active when moisture is
available. When desiccants become saturated and unable to
absorb the moisture passing into the affected area, microorganisms
can begin to grow. Dirt, dust, and other airborne contaminants
are the least recognized contributors to microbial attack.
Unnoticed, small amounts of airborne debris may be sufficient
to promote fungal growth.
1.6.8 Mechanical Stress. Manufacturing processes such as
machining, forming, welding, or heat treatment can leave
stresses in SE parts. Almost all alloys in SE construction are
sensitive to a form of corrosion known as stress corrosion
cracking. This residual stress causes corrosion to proceed
more rapidly in structurally important regions of the part until
failure occurs.
1.6.9 Time. As time goes on, metals naturally tend to corrode.
In some cases, the corrosion process occurs at the same
rate, no matter how long the metal has been exposed to the
environment. In other cases, corrosion can decrease with time
(because of the barrier formed by corrosion products) or
increase (if a barrier to corrosion is being broken down).
1.6.10 Manufacturing. During the manufacture, assembly,
or repair of SE, many factors can cause the introduction of
corrosion. Use of unsuitable materials and improper materials
processing can cause corrosion. Shearing or hole-punching
operations on some metal alloys, especially on high-strength
aluminum, may create stresses that will lead to corrosion or
provide a slight lip to inhibit complete drainage from an area.
Raised edges of the hole-punching operations may cause
incomplete drainage of electrolytes once the panels are
installed. Assembly of parts in areas contaminated by fumes or
vapors from adjacent operations may entrap fumes in the
equipment, which might lead to future corrosion. Areas without
humidity control may be sources of condensed moisture.
Inadequate or nonexistent sealant usage, improper material
selection, use of open cell foam for sound suppression are
other causes that contribute to premature structural failure of
SE.
1.6.11 Storage. Even traces of corrosive vapor in packages
containing SE parts may result in serious corrosion. Moreover,
the natural "breathing" of packages may introduce moisture
into parts and equipment. Decomposed packing materials can
emit corrosive vapors during prolonged storage, which can
create serious corrosion of equipment and the parts stored in
these packages.
1.6.12 Degradation of Non-metals. Nonmetallic materials
(plastics, elastomers, paints, and adhesives) are not subject to
electrochemical corrosion because ions are not easily formed
from nonmetallic elements and the electrical conductivity of
non-metals is extremely low. The degradation of non-metals
depends on the chemical make-up of the material and the
nature of the environment. In general, nonmetallic materials
used on equipment are selected for their performance properties
(flexibility, transparency, strength, electrical resistance,
etc.) and their resistance to heat, impact, abrasion, ultraviolet
radiation, moisture, ozone and other detrimental gases, and
operational fluids (such as hydraulic fluid, lube oil, cleaners,
deicing fluids, etc.). However, the use of unauthorized maintenance
chemicals and procedures can accelerate degradation
and ultimately lead to material failure resulting in leakage,
corrosion, electrical shorts, crazing, and/or mechanical failure.
1.6.13 Preventive Maintenance (PM). PM is probably one
of the easiest, most effective, and least expensive means of
preventing corrosion and is the process organization maintenance
personnel can control. Each type of corrosion has its
own peculiarities and will require special treatment. However,
there is a common four point approach in developing an effective
corrosion prevention and control program. The four point
approach consists of (1) the early identification of corrosion,
(2) the early and thorough removal of corrosion and proper
treatment of the corroded area (3) the complete removal of
electrolytes through frequent cleaning with approved, properly
mixed cleaning compounds, (4) and the application and maintenance
upkeep of effective protective coatings.
1.6.13.1 Corrosion can be minimized by frequent washing
because the extent of corrosion depends on the length of time
electrolytes are in contact with metals. If Qualified Product
List/Database (QPL/QPD) approved cleaners and additives are
used, frequently cleaning of equipment based or operating in a
corrosive environment will reduce the likelihood and severity
of corrosion.
1.6.13.2 Keeping chemical treatments and paint finishes in
good condition will minimize corrosion. The degradation of
nonmetallic materials can be minimized by avoiding the use of
unauthorized maintenance chemicals, coatings, and procedures.
1.6.13.3 Dedication to proper preventive maintenance practices
will maximize equipment reliability and availability.
1.6.13.4 A typical PM program should include personnel
trained in corrosion identification, prevention, thorough corrosion
removal, chemical treatment, paint removal, sealing, and
repainting. An effective PM program also includes:
a. Proper SE washing and cleaning cycle based on the corrosion
severity zone the equipment operates in.
b. Daily cleaning or wiping down of all exposed unpainted
surfaces such as actuating rods of hydraulic cylinders.
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