Abstract
The electrochemical corrosion behaviors of Ni-based superalloy nanocrystalline coating (NC) fabricated by a magnetron sputtering technique have been investigated in comparison with cast alloy in 0.25 M Na 2SO 4 + 0.05 M H 2SO 4 and 0.5 M NaCl + 0.05 M H 2SO 4 solution, respectively. Compared with cast alloy, the NC coating had a little higher passive current density in Na 2SO 4 acidic solution, while it had superior resistance to pitting corrosion in NaCl acidic solution. The semiconductive type of passive film of the NC coating was p-type in both acidic solutions, while, that of cast alloy changed from p-type in Na 2SO 4 acidic solution to n-type in NaCl acidic solution. XPS results indicated that Cr 2O 3 was the main component for the passive films of the NC coating as well as those of the cast alloy. No chloride ion was found in the passive film of NC coating while it was in the passive film of cast alloy. The chloride ions adsorbing on the surface of cast alloy incorporated into the passive film, which induced the formation of n-type oxide film. The nanocrystallization of Ni-base superalloy obviously weakened the adsorption of chloride ions on surface, which decreased the susceptibility of pitting corrosion in acidic solution.
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