Patent ID: 8580134

Claim:
A process comprising contacting an article that includes cobalt chromium alloy with a solution consisting essentially of hydrochloric acid and a chlorine-containing compound selected from the group consisting of sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl 2 ) and ammonium chloride (NH 4 Cl) for a time and at a temperature effective to form a surface oxide layer on said article that has a thickness of 20 to 40 Å and is enriched in chromium relative to said article, wherein the article includes a plurality of indentions that independently have a diameter of from about 40 to about 500 nm, wherein said solution has a concentration of H + of at least about 0.8 N to about 12 N and a concentration of Cl − greater than the concentration of H + .