Properties and Benefits of Black Oxide

Black oxide coatings offer mild corrosion protection along with a number of other benefits at an economical price.

Corrosion Protection

Black Oxide, followed by an appropriate post-treatment, provides added corrosion protection to the surface of the metal, prolonging service and increasing the shelf-life of stored parts.

Anti-Galling

The black oxide finish provides an anti-galling surface for mating parts that sacrifices the lubricating layer of black during initial contact and abrasion, while a work-hardened surface is being formed.

Lubricity

The oil-based post-treatment available for black oxide not only provides added protection against corrosion, but also produces a lubricating film for smoother running of mating parts.

Dimensional Stability

The blackening process converts the surface metal to an iron oxide by penetrating into the surface of the metal. While the process does cause a minute dimensional change (approx. 5 to 10 millionths of an inch), there is virtually no measurable increase in critical dimensions.

Surface Property Stability

Surface metal properties are maintained after black oxiding. Heat-treated parts maintain their hardness, polished surfaces retain their gloss and tool integrity is preserved.

Aesthetic Appeal

Black oxide finishing produces an attractive, decorative black finish that will enhance the perceived quality of the finished parts, thus improving sale ability.

Reduced Light Glare

The black oxide finish also reduces glare and eye fatigue in optical applications or where bright light reflection is a concern.

Conductivity

Black oxide is a suitable finish for electrical components, since there is only a 1% maximum reduction in conductivity after coating.

Resistance to colour change at high temperatures

Black oxide can be exposed to temperatures of 900 degrees F (482 degrees C) before the color of the coating begins to fade.

Free of Noxious Fumes When Welded

Black oxide coated parts do not release noxious fumes during welding, as painted or plated parts may produce.

Embrittlement Free Process

The normal black oxide process does not cause hydrogen embrittlement like some painting and plating processes. This is true, except for the unique condition of parts with a hardness of 55 Rockwell or above and for very thin springs, which are susceptible to caustic embrittlement. This problem can be minimized, however, by controlling the cycle time of the black oxide process.

Note: Parts that require pickling to remove rust or scale prior to blackening, or parts that have had a previous coating (such as zinc plating) and must be stripped prior to blackening, are susceptible to hydrogen embrittlement and may require stress relieving.

Surface Preparation

The black oxide finish improves adhesion of parts prior to painting and lacquering processes.

Economical

Black oxide is a simple, cost effective means of providing mild corrosion protection and increasing the aesthetic value of parts. It is a much faster process that saves time and money over painting or other metal finishing processes.