Nigrescence

Blackening is a common means of chemical surface treatment, the principle is to produce a layer of oxide film on the metal surface, in order to isolate air, to achieve the purpose of rust prevention.  Appearance requirements are not high can be used black processing,.  The coating film is generated by the reaction between the liquid medicine and the material of the workpiece itself. After oxidation treatment, the film thickness is 0.5-1.5 micron, which has no significant influence on the size and accuracy of the parts.  The oxidation treatment of iron and steel parts is widely used in the general protection and decoration of mechanical parts, precision instruments, cylinders, springs, weapons and daily necessities.  Its film layer wear resistance is good, dark shiny, extremely beautiful.