Black Oxide

Black oxide or blackening is a conversion coating for ferrous materials, copper and copper based alloys, zinc, powdered metals, and silver solder. It is used to add mild corrosion resistance, for appearance and to minimise light reflection. To achieve maximum corrosion resistance the black oxide must be impregnated with oil or wax. One of its advantages over other coatings is its minimal buildup.

Corrosion Protection – Depending on the post-treatment applied, black oxide coating can give corrosion resistance equivalent to 144 hrs of salt spray exposure. Other applications are designed to provide extended shelf life for stored parts prior to their use or to prepare them for further surface treatment.

Dimensional Stability – Black oxide adds no more than 5 to 10 millionths of an inch to the dimension of a part (it also penetrates to an approximate depth of 5 to 10 millionths). For all intents and purposes, the as-formed dimensions do not change (as they do when painted or plated). This provides corrosion protection for critical-size parts.