Hot corrosion of materials: a fluxing mechanism?

Hot corrosion is the accelerated oxidation of a material at elevated temperature induced by a thin film of fused salt deposit. Fused Na2SO4, Which is the dominant salt involved in hot corrosion, is an ionic conductor, so that the corrosion mechanism is certainly electrochemical in nature. Further. the acid/base nature of this oxyanion salt offers the possibility for the dissolution (fluxing) of the normally protective oxide scale. Non-protective precipitated oxide particles are often observed in the corrosion products. In this paper. the status of knowledge for the solubilities of oxides in fused Na2SO4 is reviewed, and the effects of various influences on a fluxing mechanism are discussed. An evaluation of a "negative solubility gradient" as a criterion for continuing hot corrosion is made. (C) 2001 Elsevier Science Ltd. All rights reserved.