Electrochemical performance of Ni20Cr coatings applied by combustion powder spray in ZnCL2-KCL molten salts

An investigation about the corrosion resistance of Ni20Cr coatings in ZnCl2-KCl molten salts was carried out by electrochemical techniques. Experimental conditions included static air and temperatures of 350, 400 and 450°C. 304 type SS was evaluated in the same conditions as the Ni20Cr coatings and was used as a reference material to assess the coatings corrosion resistance. Coatings were evaluated as deposited and with a grinded surface finished condition. Electrochemical techniques employed were potentiodynamic polarization curves, open circuit potential measurements and linear polarization resistance curves. Results showed that Ni20Cr coatings have a better performance than 304 type SS due to its high Ni content. The low corrosion resistance of 304 stainless steel was attributed to the low stability of Fe and Cr and their oxides in the corrosive media used. A thermochemical analysis of the Fe-Cr-Ni-Cl-O system is presented to support the results shown.