MIL-STD-171 Finishing Of Metal And Wood SurfacesThis standard establishes and updates general finish codes and serves as a general guide to the selection of suitable materials, procedures, and system for cleaning, plating, painting and otherwise finishing of metal and wood surfaces.

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MIL-STD-171F

4.5 Holes and recesses. If a method other than the one specified is necessary to attain specified thickness requirements in holes or recesses, such a method may be used upon written approval of the procuring activity. The contractor shall demonstrate that his method or methods produce the required results.

4.6 Rivets, lock bolts, blind rivets and threaded fasteners. Rivets, lock bolts, blind rivets, and threaded fasteners shall be assembled using sealant conforming to MIL-PRF-81733. Both the fasteners and the holes shall be coated with sealant. If the fasteners are dissimilar and can result in a direct contact with magnesium, a washer of 5052 aluminum alloy with a minimum overlap of one-eighth to one-fourth inch shall be used in addition to MIL-PRF-81733 sealant. Another sealing compound (-----------AMS-S-8802) may be used as a substitute for MIL-PRF-

81733 when approved by the procuring activity.

4.7 Compatibility of dissimilar metal couplings. The finishing of metals to be placed in intimate contact when assembled presents a special problem since dissimilar metal contact may results in electrolytic couples which promote corrosion through galvanic action. Table I lists metals and alloys by galvanic potential. To provide corrosion resistance intermetallic couples shall be selected so that there is 0.25 volts or less potential between the two metals or alloys.

The proper selection of metals in the design of equipment will result in fewer intermetallic contact problems caused by corrosion at the contact points. For additional information see table XVII of MIL-HDBK-2036.

4.7.1 Reduction of corrosion at intermetallic contact points. Couples of metals selected as in 4.7 shall be painted in accordance with 5.2.4.2 as a minimum requirement. When base metals intended for intermetallic contact form couples exceeding those permitted in 4.7 they shall be plated with those metals which will reduce the potential difference or they shall be suitably insulated with a nonconducting finish such as epoxy primer or other suitable means as specified. Where magnesium is one of the metals of dissimilar metal faying surfaces, the metal shall be separated by epoxy primer and/or sealing compound such as AMS-S-8802 or MIL-PRF-81733.