Seven kinds of corrosion tests were carried out on thirteen kinds of nickel-based alloys in subcritical and supercritical water containing 0.01 mol/kg sulfuric acid (H2SO4) and 800 ppm oxygen (O2) using a Ni-44Cr-1Mo autoclave. The obtained corrosion rates were significantly lower than the previous experiments performed under the same conditions using a titanium autoclave. A compact oxide scale was found on the specimens tested in the Ni-44Cr-1Mo autoclave. The chromium-rich oxide layer would originate from the autoclave material and provide a protective function against corrosion. The corrosion retardation phenomenon has been explained by dependencies of chromia (Cr2O3) solubility on the phase state of water and temperature.

Subject
Scanning electron microscopy, Supercritical water, Materials, Corrosion rate, Nickel based alloys, Chromia, Autoclaves, Chromium, Corrosion testing, Solubility, Commercial alloys, Ion concentrations, Titanium
Keywords:
chromium ion, chromium oxide, deposition, nickel-based alloy, oxide scale, solubility of oxide, supercritical water
NACE International
2007
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