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 alkaed 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.