EVALUATION OF HIGH-TEMPERATURE CORROSION-RESISTANCE OF AL PLASMA SPRAY COATINGS IN MOLTEN SULFATES AT 1073-K BY ELECTROCHEMICAL MEASUREMENTS

Measurements of polarization curves were made to evaluate the corrosio n resistance of Al plasma spray coatings in 50 mol%Na2SO4-50 mol%Li2SO 4 melt at 1073 K. The results showed that substrate materials have a g reat effect on the corrosion resistance of Al plasma spray coatings. A lso, it is found that the corrosion resistance of Al plasma spray coat ings can be improved through diffusion treatment in argon atmosphere. The effects of diffusion treatment conditions on Al plasma spray coati ngs were investigated in detail. The results obtained from electrochem ical measurements were well correlated with those of X-ray diffraction , SEM observation and EPMA analysis.