CORROSION POTENTIAL BEHAVIOR IN HIGH-TEMPERATURE WATER OF NOBLE METAL-DOPED ALLOY COATINGS DEPOSITED BY UNDERWATER THERMAL SPRAYING

The electrochemical corrosion potential (ECP) of type 304 (UNS S30400) stainless steel (SS) coated under water by hyper-velocity oxy-fuel (H VOF) and plasma-spray (PS) techniques using noble metal-doped powders was measured to evaluate the catalytic behavior in high-temperature wa ter under various water chemistry conditions. Thermal-spray coatings o f noble metal-doped powders exhibited catalytic behavior for the recom bination of oxygen and hydrogen in high-temperature water, which cause d ECP to decrease well below a critical value of -230 mV(SHE) for inte rgranular stress corrosion cracking (IGSCC) protection in water. This was observed in water containing various amounts of oxygen and hydroge n peroxide (H2O2) when stoichiometric excess hydrogen was present.