What is the metal blackening process? Put the part in a liquid and an interesting phenomenon occurs

Blackening processing, also known as bluing treatment. All kinds of metal products in contact with the air for a long time, it is easy to be oxidised and corroded from the surface, blackening is a common means of metal heat treatment, the principle is to form a layer of oxidative film on the metal surface, that is, tetra-ferric oxide oxide film, in order to isolate the air, to achieve the purpose of rust, but also to increase the surface gloss of the metal parts, so that it is more beautiful.

In terms of efficiency and cost, blackening treatment processing time is short, low cost, safe operation, and at the same time can reduce part of the internal or external deformation caused by the workpiece. So it is widely used in metal surface treatment.