The thermal spray coating technique was used to produce insulated protective coatings (IPC) on Type 304 (UNS S30400) stainless steel (SS) surfaces. The electrochemical corrosion potential (ECP) response and flow-assisted corrosion (FAC) rate were then evaluated in high-temperature water under various water chemistry conditions. The ECP results clearly demonstrate that the IPC layer created with a powder of yttria-stabilized zirconia (YSZ) restricted oxidant transport to the metal surface, and the ECP remained at <–500 mV vs. standard hydrogen electrode (SHE) in 288°C water containing 700 ppb to 900 ppb oxygen (O2) and no hydrogen (H2). In addition, no significant weight loss of the YSZ coating was measured after a 10-week immersion, and the presence of noble metals on the YSZ coating layer did not alter the ECP behavior of the YSZ-coated Type 304 SS.

Subject
Water, Coatings, Metal surfaces, Noble metals, Water chemistry, Oxide surfaces, Surface layers, Oxygen, Immersion, Electrodes, Corrosion potential, Electrode potential, Hydrogen
Keywords:
boiling water reactor, electrochemical corrosion potential, high-temperature water, insulated coatings, noble metal, plasma spray, yttria-stabilized zirconia
NACE International
2005
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