Ceria (CeO2) based coating for high temperature corrosion protection of 9Cr-1 Mo steel

Abstract

Ceria (CeO2) based high temperature coating was developed over 9Cr-1 Mo steel substrate. The coating is produced by plasma spray coating method by using robotic arm. Isothermal corrosion study of the CeO2 coated and uncoated specimen was conducted at 973 K for 8 h. The corrosion rate and reaction kinetics were studied and the post corroded scales were characterized in SEM, EDS and XRD. The results clearly indicate that ceria (CeO2) coated specimen improves the high temperature oxidation resistance than uncoated specimens. The kinetic behaviour of both coated and uncoated specimen follows approximate parabolic growth rate which further indicates that the corrosion is diffusion controlled growth. The post corroded scale of the coated specimen shows fine grained oxide scale with no scale cracking and detachment. The improvement of oxidation resistance in presence of CeO2 coating can be attributed to the formation of fine grained oxide on the scale, changed mechanism of scale growth from outer cation migration to inner anion migration and enhancement of scale adhesion with the substrate. The detail mechanism of the oxidation of CeO2 coated specimen and uncoated specimen is further discussed in this paper.