No experience with it, several products offered on the market, but I was wondering if the end finish is durable, a couple of the advertised products call for a clearcoat as a last step. That sounds like the blackening is not durable at all. .......
Lots of detailed information readily available that mostly says true blackening of the stainless steel metal is an EPA regulated hazmat producing industrial process including such fun things as molten salt baths for actual blackening.
All over including bore or exterior only is another major concern.
As for a top coat and
durable durable under what circumstances of abrasion or chemical (including atmospheric water) exposure? BirchWood Casey suggests:
Black oxide finishes do require a sealant of some type because the black finish itself has a porous crystal structure. Although the sealant is primarily responsible for the corrosion resistance, the underlying black coating acts as an absorbent base, holding the sealant in contact with the metal substrate.
Durable enough; remember that for many years many people complained about holster wear with gun coatings and complaints have lessened with more careful higher heat applications.
I suggest for a first approximation deciding on the objective.
Coloring stainless steel or
coating stainless steel? Folks have been known to plate with mild steel then color the mild steel or paint with anything from undercoating/bed liner for protection to a full range of Cerekote and competition brand colors.
Not much point in cutting and pasting industry instructions and anything less is liable to be incomplete and misleading.
As always YouTube is full of folks showing how they did it - mostly smaller pieces that are easier to handle for uniform results than a barrel - while Birchwood Casey and others offer full and complete instructions on the process in general and the use of their respective products.