Blackening of Steels

Black oxide or blackening is a surface coversion process mainly used on ferrous materials, including low carbon steels, alloy steels, tool steels and stainless steels.  It is used to add an attractive black appearance, to improve corrosion resistance and to minimize light reflection. After blackening, the oxide is impregnated with oil, wax or other water displacement sealants.

Gun-bluing falls under the banner of “blackening” although it can be applied by purely a thermal process as well. DIY shops often use a blow torch and an oil quench to give a bluing effect, however this is not a uniform coating nor does it conform to military specifications.

The TDCC runs the high temperature alkaline oxidizing blackening cycle with water displacement sealer. This is done according to MIL-DTL-13924D Class 1.

The advantage of this process is:

  • an attractive black appearance
  • added corrosion resistant (NSS> 100 hrs)
  • no significant impact on dimensions


To further reduce reflectivity, items are fine-grit shot blasted to a specific surface finish prior to treatment.

Contact the TDCC regarding your specific requirements.