MIL-STD-1250 Corrosion Prevention And Deterioration Control In Electronic Components And Assemblies S/S By Mil-Hdbk-1250This standard establishes minimum requirements for procedures, materials and systems for protecting electronic components in DoD systems and assemblies from adverse environments. Protective measures shall be sufficient to maintain performance characteristics within specified limits both during and after exposure to moisture, high and low temperatures, corrosive gases, chemicals and microbial fungal attack.

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MIL-STD-1250A

5.4 Ferrous Metals.

5.4.1 Corrosion resistant steels. Corrosion resistant steels shall be passivated in accordance with QQ-P-35. No further finish is required to provide corrosion resistance to steels of the 300 series. Where tarnish, rust or surface stain is objectionable, the 400 series and precipitation hardening steels shall be given additional protection by a suitable plating or paint finish after passivation.

5.4.2 Carbon and low alloy steels. Ordinary iron and steel shall be coated with cadmium, nickel or tin except as follows:

a. Precision parts which are totally and continuously immersed in oil, grease, encapsulant or moisture-proof coating, or which are contained in hermetically sealed units, need not be given any further protection. Local application of oil or grease shall not automatically be considered corrosion protection.

b. Laminations used in magnetic circuits need not be plated if they are otherwise protected from corrosion

c. Springs shall preferably be given organic coatings, or be coated by ion deposition or other non-hydrogen-producing processes, rather than electroplated

d. Structural parts may be cleaned, primed, and painted in accordance with MIL- STD-186 or applicable specifications

e. Close tolerance parts, not exposed to outdoor atmosphere, may be protected with approval of the procuring activity by corrosion preventive compounds such as MIL-C-81309, MIL-C-16173, MIL-C-11796, MIL-L-87177, or MIL-C-85054.

5.5 Nonferrous metals. The noble metals (gold, palladium, platinum and rhodium) and the corrosion-resistant metals (chromium, nickel, and titanium) require no finish other than cleaning. Surface finish for electrical bonding or grounding is listed in 5.8 and table II. Applications of aluminum and copper shall receive the protection specified in 5.5.1 and 5.5.2 unless in hermetically sealed units.

5.5.1 Aluminum. All aluminum and aluminum alloys shall be anodized in accordance with MIL-A-8625, then primed with MIL-P-23377 or equivalent and given a suitable top coat and painted with MIL-C-46168, except as follows:

a. In areas of electrical bonding (see 5.8.1)

b. For applications where anodizing is not required, chemical film treatment in accordance with MIL-C-5541 may be used, although it is not to be considered to afford corrosion protection equivalent to anodize. Whenever possible, chemical films shall be given the additional protection of organic coatings.

c. For applications involving continued exposure to elevated temperatures, where the resultant oxide buildup is objectionable (such as heat sinks) consideration shall be given to metallic coatings with suitable thermal characteristics in lieu of anodize.