Oxidation and alkali sulfate-induced corrosion of aluminide diffusion coating with and without platinum

A platinum-free (MDC210) and a platinum-rich (MDC150L) aluminide diffusion coating applied to a CMSX4 single crystal Ni-based superalloy were investigated after exposure to sulfate-induced corrosion and oxidation at 900 degrees C for a total of 100 h. Weight changes, microstructural, and microchemical analyses of the products were performed by the means of gravimetry, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD). Platinum was found to have a beneficial effect on both the oxidation and corrosion resistance of the coating. In both cases the scale was thicker on the platinum-free coating. However, the difference in the extent of oxidation of the two coatings was small