Corrosion of nickel-chromium alloys by molten glass at 1100°C:: An electrochemical study

The corrosion of Ni-Cr alloys in molten glass has been studied with classical electrochemical methods. After the determination of the electrochemical properties of the glass on a platinum electrode, corrosion potential measurements, anodic and cathodic polarizations and polarization resistance measurements have been performed on Ni-Cr alloys. Free potential measurements were used to determine the corrosion reactions involved. Anodic and cathodic polarizations showed that Ni-Cr alloys in molten glass have similar behavior to stainless steels in acidic solutions : active dissolution, passivation and transpassivation. Concerning corrosion current evaluation, the Tafel method is not very suitable because of the high working temperature. Polarization resistance method is much more accurate. In the glass studied, a relation between corrosion current and chromium content of Ni-Cr alloys has been established : low and high chromium content alloys have a corrosion current more than a decade higher than Ni-Cr alloys with intermediate chromium content.