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TM 10-4930-369-13&P
CORROSION PREVENTION AND CONTROL (CPC)
Corrosion prevention and control of Army materiel is a continuing concern. It is important that any corrosion
problems with this item be reported so that the problem can be corrected and improvements can be made to
prevent the problem in future items. The term "corrosion" means the deterioration of a material or its properties
due to a reaction of that material with its chemical environment. An example is the rusting of iron. Corrosion
damage in metals can be seen, depending on the metal, as tarnishing, pitting, fogging, surface residue, and/or
cracking. Plastics, composites, and rubbers can also degrade (also considered to be corrosion based on the above
deinition of corrosion). Degradation is caused by thermal (heat), oxidation (oxygen), solvation (solvents), or
photolytic (light, typically ultraviolet) processes. The most common exposures are excessive heat or light. Damage
from these processes will appear as cracking, softening, swelling, and/or breaking. The US Army has deined
the following nine (9) forms of corrosion used to evaluate the deterioration of metals. These shall be used when
evaluating and documenting corrosion.
Uniform: Affects a large area of exposed metal surface, like rust on steel or tarnish on silver. It gradually reduces
the thickness of the metal until it fails. Metal deterioration caused by corrosion on the bonds between or across the
grain boundaries of the metal. The metal will appear to be peeling off in sheets, laking, or being pushed apart by
layers. A particular type of inter-granular corrosion is exfoliation.
Crevice: Occurs in crevices created by rubber seals, gaskets, bolt heads, lap joints, dirt or other surface deposits.
It will develop anywhere moisture or other corrosive agents are trapped and unable to drain or evaporate.
Selective Leaching: One element, usually the anodic element of an alloy, corrodes away, leaving the cathodic
element. This can create holes in metal.
Intergranular: Metal deterioration caused by corrosion on the bonds between or across the grain boundaries of the
metal. The metal will appear to be peeling off in sheets, laking, or being pushed apart by layers. A particular type
of intergranular corrosion is exfoliation.
Pitting: This can result from conditions similar to those for crevice corrosion. Pits can develop on various materials
due to their composition. Rile boxes are big victims of pitting.
Erosion: Results when a moving luid (liquid or gas) lows across a metal surface, particularly when solid particles
are present in the luid. Corrosion actually occurs on the surface of the metal, but the moving luid washes away
the corrosion and exposes a new metal surface, which also corrodes.
Fretting: Occurs as a result of small, repetitive movements (e.g., vibration) between two surfaces in contact with
each other. It s usually identiied by a black powder corrosion product or pits on the surface.
Galvanic: Occurs when two different types of metal come in contact with each other, like steel bolts on aluminum,
for example. This is a common problem on aircraft because of their mix of metals.
Stress: Term used to describe corrosion cracking and corrosion fatigue. Where an item is not ready/available
due to one of these forms of corrosion, it shall be recorded as a corrosion failure in the inspection record and the
appropriate code (170) for corrosion shall be used when requesting/performing maintenance.
SF Form 368, Product Quality Deiciency Report should be submitted to the address speciied in DA PAM 750-8,
The Army Maintenance Management System (TAMMS) Users Manual.
OZONE DEPLETING SUBSTANCES (ODS)
None.
DESTRUCTION OF ARMY MATERIEL TO PREVENT ENEMY USE
Refer to TM 750-244-3 for instructions on destruction of Army materiel to prevent enemy use.
PREPARATION FOR STORAGE OR SHIPMENT
Information for preparing for storage or shipment is in WP 0018.
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