Corrosion Kinetics of Al2O3+Zro2·5cao Coatings Applied on Gray Cast Iron Substrate

Abstract

A Corrosion test was carried out on plasma sprayed alumina plus calcia stabilized zirconia coatings applied on the Gray Cast Iron (GCI) substrates. The specimens were prepared by coating a bond coat comprising Fe38Ni10Al and a top coat of Al2O3+ZrO2·5CaO in 50:50 proportions on GCI substrates. The top coat thickness was varied as 100,200 and 300 µm. In the test, specimens were exposed to the saline aqueous NaCl solution for a period of 24 h. Weight loss of specimen was measured at the interval of 8 h followed by Scanning Electronic Microscopic (SEM) and EDAX analysis. From the results obtained, it was found that the iron present in the bond coat of the sample was subjected to corrosion. It led the way to the formation of hydrated iron oxide (Fe2O3H2O) which is visible on the top coat of specimens. Pores present in the coating system and relatively less coating thickness has mainly attributed for the corrosion of bond coat.