Hydrothermal deposition of zirconia coatings on pre-oxidized BWR structural materials

An in situ hydrothermal deposition process is being developed to apply a thin coating of zirconia onto the structural materials used in Boiling Water Reactors as a potential method for mitigating intergranular stress corrosion cracking. The process has successfully deposited ZrO₂ onto as-received interior surfaces of 304 stainless steel and Alloy 600 tubes [Z.F. Zhou, E. Chalkova, S.N. Lvov, P. Chou, R. Pathania, Corros. Sci. 49 (2007) 830]. This paper discusses the application of the coating on specimens with different surface conditions: as-received; ground to remove the as-received surface; and ground and pre-oxidized. For comparable deposition parameters and for a given substrate, the different surface conditions did not influence the morphology or the thickness of the coating, but had a substantial impact on adhesion. As in our previous study, electrochemical potentials of the coated specimens in simulated BWR environment were not clearly lower than those of uncoated specimens [Zhou et al., 2007].