Anodic, polarisation of Nimocast 713 in sulphate melts containing zinc

Author： Maclssac L.M. Caley W.F. Hancock H. A. Hollingshead R. S.

ISSN： 1743-2847

Source： Materials Science and Technology, Vol.4, Iss.11, 1988-11, pp. : 1035-1038

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

The hot corrosion of superalloys results from deposits of sulphates which form a liquid phase at the operating temperature. The rate of the hot corrosion can be inhibited by the addition of zinc to the sulphates. Anodic polarisation studies were carried out in a ternary eutectic salt mixture (78LiSO₄−13·5K₂S O₄−8·5Na₂S O₄, in mol.-%) at 900°C to ,determine whether the zinc inhibited the corrosion by affecting the electrode kinetics of the alloy, in this case Nimocast 713. The addition of 10 wt-%ZnSO₄ decreased the corrosion current and made the corrosion potential more positive by apparently changing the anode half cell potential. In the presence of zinc in the molten salt electrolyte, the alloy also exhibited some passivation over an anodic potential range of about 0·4 V. Examination of the microstructure of the electrodes at the metal/molten salt interface did not reveal any significant concentration of zinc.MST/621