Nigrescence_blackening_treatment

Nigrescence   is a chemical surface treatment, its main role is a dense layer of oxide film formed on the surface of the workpiece, the workpiece to prevent rust corrosion, improve the wear resistance of the workpiece, it is only a surface treatment does not produce any effect on the internal organization, it is not heat-treated, and quench a fundamental difference. Blackening treatment methods are now commonly used conventional alkaline heated black, appeared later in the steam room temperature blackening and black etc.. But temperature oxidation process for the low-carbon steel is not very good. Basic black subdivision out there a difference between black and two black. Blackening of the main ingredient is sodium hydroxide and sodium nitrite. When the desired temperature tolerance black larger, probably between 135 到 155 ℃ can get a good surface, but some of the length of time required for it.