Superior protective performance of Ni–Cr coating on stainless steel 316L in pure, oxygenated and chlorinated supercritical water

The protective effect of Ni–Cr coating in supercritical water (SCW) was studied in this work. Ni–Cr coated 316 L stainless steel showed an excellent microstructure and performance stability in SCW. The corrosion weight gains of as-received 316L were 2–3.6 times of that of Ni–Cr coated sample in SCW with 5000 ppm oxygen content. The coating greatly reduced the corrosion weight gain of 316L in a SCW environment after 144 h exposure. The surface of Ni–Cr coating was composed of the outermost hydration layer (Ni(OH)₂), oxide layer (NiO, NiCr₂O₄ and Cr₂O₃) and metallic layer (Ni⁰) mixed in oxides. NiO on the surface of the Ni–Cr coating decomposed with the addition of oxygen or chloride ions in SCW.