Treatment of refractory metals or alloys based thereon

Full Title

Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals > using aqueous solutions > using aqueous acidic solutions with pH less than 6 > not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates > Treatment of refractory metals or alloys based thereon