The operating temperatures at which mechanics perform the black oxide surface treatment process vary, and these temperatures determine the different types of black oxide coatings. They include:

Hot oxidized black surface treatment

Thermal oxidation black surface treatment is the most common type of black oxidation surface treatment. It requires the part to be immersed in a high-temperature salt bath, using a salt bath including caustic soda (NaOH), nitrate or nitrite. The temperature range of the process is typically between 275 and 295 degrees Fahrenheit.

The temperature of the black oxide coating process must be maintained within this range. Because the lower temperature will prolong the process time, and the higher temperature will lead to rust on the surface of the finished parts.

Medium temperature oxidized black

This process is similar to the thermal oxidation black surface treatment, the difference is only that the operating temperature is different. Operating temperatures range from approximately 194 to 248 degrees Fahrenheit. This temperature also converts the metal into magnetite. However, compared with the thermal oxidation black surface treatment, it has the advantage that no corrosive fumes are produced during processing.

Cold oxide black

This process is also known as room temperature oxidation black. Unlike other types of methods, this process deposits copper selenide on a metal surface at a temperature of 68-86 °F. The black oxide surface produced by this process does not wear as well as other processes.