Electrochemical studies on hot cocrosion of Ni-Cr-Al Alloys in molten Na2So4-Nacl

Abstract

The hot corrosion behavior of Ni-20%Cr-2%Al and -5%Al alloys in molten Na2SO4-NaCl was examined by the electrochemical measurement, the measurement of corrosion mass loss and the observation of corrosion morphology. The corrosion mass loss of both alloys was very large in mixed molten salts of Na2SO4 and NaCl. In the mixed molten salts, correspondingly, the anodic and cathodic reactions of the alloys in the vicinity of corrosion potential were very active. This suggests that this hot corrosion results from an electrochemical reaction. In addition, the electrochemical studies also indicated that the anodic and cathodic reactions for the hot corrosion seemed to be a preferential dissolution reaction of chromium from the alloys and a reduction reaction of [formula omitted] ions due to the dissolution reaction, respectively. This reaction model was supported by the observation results of a corrosion layer formed in the alloys. It was thought that such electrochemical corrosion was accelerated by a corrosion product. © 1992, The Japan Institute of Metals. All rights reserved.