Chemical activation of self-passivating metals

A process for simultaneously depassivating and surface hardening a workpiece without formation of nitride or carbide precipitates, the workpiece being made from a corrosion-resistant, self-passivating metal comprising a stainless steel containing 5-50 wt. % Ni and at least 10 wt. % Cr, a nickel-based or manganese-based alloy containing at least 10 wt. % Cr or a titanium-based alloy, the workpiece having one or more surface regions which define a Beilby layer as a result of a previous metal shaping operation, the surfaces of the workpiece also having a coherent protective coating formed either from chromium oxide or titanium oxide, the process comprising contacting the workpiece with vapors produced by heating a non-polymeric N/C/H compound to a processing temperature which is high enough to convert the non-polymeric N/C/H compound to vapors, wherein the non-polymeric N/C/H compound (a) contains at least one carbon atom, (b) contains at least one nitrogen atom, (c) contains only carbon, nitrogen, hydrogen and optionally halogen atoms, (d) is solid or liquid at 25° C. and atmospheric pressure, and (e) has a molecular weight of ≤5,000 Daltons, wherein the processing temperature is less than 500° C. and also below a temperature at which nitride and/or carbide precipitates form thereby depassivating the workpiece by making its coherent protective coating transparent to the passage of nitrogen and carbon atoms and simultaneously surface hardening the workpiece by causing carbon and/or nitrogen atoms to diffuse into the surface of the workpiece without formation of the type of carbide and/or nitride precipitates which cause the corrosion resistance of the self-passivating metal to be lost.