ackened Finish Nuts
A chemical black finish is also referred to as black oxide or blackening. It is a ‘conversion coating’, which is a coating for metal where the surface of the part is subjected to a chemical or electrochemical process by the coating material, converting it into a decorative or protective substance. Chemical blackening is often used on fasteners made from stainless steel, copper, copper based alloys and zinc. Benefits of the process include the addition of mild corrosion resistance, improves aesthetic appearance and the minimizing of light reflection. Maximal corrosion resistance can be achieved when the oxide is impregnated with oil or wax. A chemical black finish with stainless steel uses hot black oxide which is a mixture of caustic, oxidizing and sulfur salts, and can be used on cast iron and low-carbon steel. There is also room-temperature blackening for stainless steel, which offers less abrasion resistance but similar corrosion protection as a hot blackening process. The process essentially involves embedding a pigment into the fixing which unlike paint or plating, does not alter the precise dimensions or surface texture.