Monitoring of Degradation Process of Alloys and Al Diffusion Coatings under Molten Sulfate Film by Electrochemical Impedance Measurements

Abstract

The hot corrosion behaviors of several alloys and Al diffusion coatings were evaluated by electrochemical impedance technique under molten sulfate film with a special designed electrochemical cell. It was found that corrosion resistance of alloys changed greatly with the changing of atmosphere. For alloys, the atmosphere has much greater effect on corrosion behavior under molten salt film than in bulk molten salt. Meanwhile, Atmosphere did not have significant effect on corrosion behavior of Al diffusion coatings probably due to the instant formation of protective aluminum oxide film under any atmosphere tested. More information about changes in aluminum oxide film properties was also obtained by impedance monitoring. Electrochemical technique was proved to be very useful for the evaluation of hot corrosion resistance of both alloys and protective coatings under molten salt film condition.