Cathodic Corrosion of Chromium in Molten Na2SO4
Motoi Hara, Shozo Hatanaka, Tokiko Nakagawa, Yutaka Shinata
The corrosion behavior of chromium under catholic polarization in molten Na2SO4 at 1173K has been investigated. The loss of chromium under catholic polarization in the molten salt increased with an increase in the quantity of electricity for the cathodic reaction. In order to examine the mechanism of catholic corrosion of chromium in the molten salt, direct observation of the chromium electrode under catholic polarization and identification of corrosion products were conducted. A black turbidity near the chromium electrode was observed in the melt during catholic polarization, suggesting a generation of corrosion product from the electrode. It was found that the corrosion product consisted of Cr2O3. Investigation of the cathodic polarization reaction showed that a two-electron reduction reaction of SO42- occurred under catholic polarization in molten Na2SO4. Consequently, it was proposed that catholic corrosion for chromium in molten Na2SO4 occurred by a chemical reaction of the chromium with SO32- and O2- which appeared as catholic products.