Development of a hydrothermal deposition process for applying zirconia coatings on BWR materials for IGSCC mitigation

An in situ hydrothermal deposition process is being developed to apply a film of zirconia (ZrO2) onto interior surface of 304 stainless steel and Alloy 600 as a potential method for mitigating intergranular stress corrosion cracking (IGSCC) in boiling water reactors (BWRs). The coating process is discussed. The obtained zirconia coatings are adherent. Monoclinic ZrO2 is the dominant phase when ZrO(ClO4)2 was the oxidant; tetragonal ZrO2 became the dominant phase when ZrO(NO3)2 was the oxidant. A preliminary experiment did not measure significantly lower values of the electrochemical potential (ECP), relative to the uncoated specimen over a wide range of dissolved oxygen in 265 °C water.