Black Oxide Coatings

General Details and Specification of black oxide finishes

Black Oxide, Blackening, Oxidizing, Oxiding, Black Passivating, Gun Bluing . . . these terms all refer to the process of forming a black iron oxide on the surface of metals. Mostly a decorative coating. Only very limited corrosion protection under mild corrosion conditions. Black oxide coatings should normally be given a supplementary treatment (i.e. oil displacement per MiL-C-16173 Grade 3 or protective treatments of MiL-C-16173).

Benefits of black oxide

  • Corrosion Protection
  • Produces a lubricating film for smoother running of parts
  • Dimensional Stability
  • Black oxide finishing produces an attractive, decorative black finish
  • Black oxide finish reduces glare and eye fatigue
  • Free of Noxious Fumes When Welded
Specs Thickness Comments
MIL-DTL-13924D No dimensional change For moving parts that cannot tolerate the dimensional change of a more corrosion resistant finish.
Class I No dimensional change Alkaline oxidizing process (for wrought iron, cast and malleable irons, plain carbon, and low alloy steels.
Class 4 No dimensional change Alkaline oxidizing process (for other corrosion resistant steel alloys).

Chemical Finish: black

A uniforrn black corrosion retardant for copper. Coating has no abrasion resistance.

Specs Thickness Comments
M1L-F-495E No dimensional change Used as a base for lacquer, light oil, or wax. For decorative, optical, and corrosion retardant applications.