BLACKENING OF STAINLESS STEEL
Robar is able to blacken stainless steel through the use of oxidizing type blacking compounds. This process produces black coatings on stainless steel and alloy steels by a "conversion" process. The chrome in the stainless steel is involved in a chemical reaction with the oxidizers in the solution producing chrome-sulfide. The application of the black finish is dependent upon the surface treatment of the steel. Bead blasted surfaces will have a satin black appearance while a surface blasted with aluminum oxide will be matte in nature. Importantly, dimensional changes involved in blackening are extremely small, less than 0.0001 Mil. This thickness of the black oxide type coating ranges from 0.00006-0.0001 Mil depending on the type of alloy being treated. Blackening of stainless steel not only makes the weapon more attractive but adds to its corrosion resistance (96 hours salt spray per Mil-C-13924B) and aids in preventing galling, common in stainless steel guns.

.....from ROBARs website.



I had Robar's treatment of NP3 internals/Black exterior of my ULA 300WSM. It has a stainess Douglas barrel that is now black. They did a good job - I'm well pleased.



Jeff