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

aa.        Equipment and components mounted directly to compartment floors where standing water is possible.

4.2  Unacceptable materials.  The following materials shall be considered unacceptable in equipment design:

a.         Magnesium

b.        Aluminum alloy 2024-T3 or 2024-T4 (use 2024-T8 or 5000/6000 series aluminum alloys)

c.         Aluminum alloy 7075-T6 (use 7075-T73 or 7050-T76)

d.         Precipitation hardening steels in H900, H950, or H1000 tempers e.         Graphite lubricants

f.          Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC)

g.        Corrosive-type RTV silicone rubber sealant (yields acetic acid during cure)

h.         Rubber that is susceptible to ozone damage

i.        Teflon-insulated silver plated hookup wire shall only be used with prior approval of the procuring activity

J.        MIL-C-5541  (Class 3)  conversion coating on aluminum (use anodized or class 1A treatment)

k.         Cadmium plating in accordance with QQ-P-416, Type I (use Type II)

l.          Gold plated electrical contacts with a nickel undercoating m.        Silver plated electrical contacts

n.         Nickel plated aluminum construction

o.         Potting materials and/or foam materials that are reversion-prone p.         Materials not inherently moisture and fungus-resistant

q.         RA solder flux

r.          Gold over silver or copper without a barrier coat of nickel s.         Organic materials that outgas corrosive vapors

t.          Polymide insulation.

4.3  Cleaning.  All surfaces shall be thoroughly cleaned before Joining, coating, potting, impregnating, or encapsulating.  Surfaces shall be cleaned after brazing, soldering or welding to remove contaminants.  General cleaning shall meet the requirements of

MIL-S-5002 and the cleaning of high reliability electronic parts shall be in accordance with MIL-STD-2000.  High strength steels (over 180 ksi or HRC 40) shall not be cathodically cleaned in either acid or alkaline baths and shall not be acid cleaned except anodically. Organic solvents for use on plastics shall be selected with care to avoid crazing or other

damage to the plastic.  For vapor degreasing, solvent cleaning and drying, only those materials and procedures listed in MIL-STD-186 shall be used.  Care shall be taken that cleaning materials are compatible with all materials in the part or assembly.  Dust, dirt and fingerprints shall be removed prior to assembly or storage.

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