Sodium chloride can be present in gas turbine hot sections in the vapor as well as the condensed state. Particles containing sodium chloride may randomly break from compressor components, then impinge upon and stick to turbine components further down the gas path. However, NaCl vapor can deleteriously affect processes involving the formation and maintenance of protective oxide layers on turbine components. The relative importance of these two distinctly different mechanisms involving NaCl in corrosion processes is currently unknown. Numerous studies have dealt with the effect on corrosion behavior of Na2SO4-NaCl condensed mixtures with appreciable amounts of NaCl. However, the possibility that low NaCl vapor activities effect major changes in oxide scale formation and retention is equally as probable as that involving condensed NaCl. Therefore, the results presented here will deal with effects of low activities of NaCl vapor (0.1–100 ppm) upon scales formed by selected high temperature materials.

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