Black Oxide Industries
Black Oxide Coating process was originally developed during the early 1900’s. The modern bath become commercially prevalent during the later 1930’s and has remained so through today. With little advancement to the actual chemical process, Black Oxide Industries' commitment to continuous improvement in techniques, education, and latest technology has advanced BOI to the top of the Chemical Conversion Coating profession.
Black Oxide process applies to ferrous, non-ferrous, brass and copper alloy. The Black Oxide is a true conversion coating converting iron to the naturally occurring black iron oxide compound called magnetite. The magnetite is produced through chemical reaction as the alloy is immersed into the hot blackening solution. Dwell times depend on such parameters as base alloy, part density, surface hardness, and nature of the heat treated surface. The Black Oxide conversion will not reduce hardness or affect the dimensional characteristics of the finished part. Producing no appreciable dimensional change, it has been documented to be measured at 5 millionths of an inch. The coating becomes an integral part of the base metal surface and does not chip, peel, crack, or rub off. When aesthetics are specified, note that the gloss level or shade of black cannot be controlled. The finish is dependent on the condition or finish of the base material. The desired gloss level may be achieved prior to the Black Oxide process through mechanical means. Machining, polishing, line-graining, abrasive blast, polishing and buffing, all play an integral part in achieving a desired shade or gloss level of black color. Black Oxide is considered as a non-sacrificial coating, meaning it offers a limited amount of corrosion protection and generally is specified when dimensional build-up of a more corrosion resistant finish cannot be tolerated.
BOI performs Black Oxide processes certifying to various aerospace, military, and prime customer specifications:
MIL-DTL-13924 Class 1, 2, 3, & 4 (steel & stainless steel)
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