The activation/depassivation of nickel–chromium–molybdenum alloys in bicarbonate solution: Part I

Electrochemical and surface analytical techniques (X-ray photoelectron and Auger spectroscopies) were used to characterize the influence of potential on the properties of the oxide film formed on the Hybrid BC-1 (a Ni–Cr–Mo) alloy in chloride solutions containing bicarbonate. In the passive region the film possesses the expected bilayer structure with a Cr(III)-dominated barrier layer containing mixed oxidation states of Mo and an outer dominantly-hydroxide layer. At more positive potentials the Cr/Mo content of the film decreases when bicarbonate is present and the alloy becomes covered by a thick (>100 nm), and only partially protective, Ni(OH)2 layer