NPFC - MIL-DTL-13924

scope:

This specification covers black oxide coatings applied to ferrous metals (carbon, low alloy, and corrosion resistant steels, and wrought iron). Black oxide coatings, with or without a supplementary preservative treatment (see 3.11), may be used where a black surface is required. Only very limited corrosion protection, under mildly corrosive conditions, is obtained as a result of black oxide coating (see 6.1). Black coatings are included in this specification with limitations as noted in 1.2. Unless contraindicated by contract, chrome-free finishes should be used in place of finishes containing hexavalent chromium, provided all performance criteria herein has been met and documented as OQE.

Classification. Black oxide coatings covered by this specification should be of the following classes as specified (see 6.2 and 6.3.2).

Class 1 Alkaline oxidizing process (for wrought iron, cast and malleable irons, and plain carbon or low alloy steels).

Class 2 Alkaline chromate oxidizing process (for use on certain corrosion resistant steel alloys which are tempered at less than 900°F (482°C)).

Class 3 Fused salt oxidizing process (for corrosion resistant steel alloys which are tempered at 900°F (482°C) or higher).

Class 4 Alkaline oxidizing process (for other corrosion resistant steel alloys).

intended Use: