Corrosion Potential Behavior in High-Temperature Water of Noble Metal-Doped Alloy Coatings Deposited by Underwater Thermal Spraying

Abstract

The electrochemical corrosion potential (ECP) of type 304 (UNS S30400) stainless steel (SS) coated under water by hyper-velocity oxy-fuel (HVOF) and plasma-spray (PS) techniques using noble metal-doped powders was measured to evaluate the catalytic behavior in high-temperature water under various water chemistry conditions. Thermal-spray coatings of noble metal-doped powders exhibited catalytic behavior for the recombination of oxygen and hydrogen in high-temperature water, which caused ECP to decrease well below a critical value of –230 mVSHE for intergranular stress corrosion cracking (IGSCC) protection in water. This was observed in water containing various amounts of oxygen and hydrogen peroxide (H2O2) when stoichiometric excess hydrogen was present.