Corrosion Behavior of 316L Stainless Steel in City Sewage Sludge Treated by Supercritical Water Oxidation

The corrosion behavior of 316L stainless steel netlike and block samples was studied in city sewage sludge treated by supercritical water oxidation (SCWO). The results showed that the corrosion of 316L was enhanced as the oxidation coefficient increased. Filament mineral salts rich in Mo and Ni were found on the outer surface of the net like sample under alkaline condition. Different from the net like sample, on the block sample pitting corrosion morphology was observed under the acidity and high oxidation conditions. 316L had the highest corrosion rate of 0.17 mm/a under the acid SCWO condition. The surface oxide on the block sample was mainly Fe₃O₄-NiFe₂O₄ and pitting corrosion was observed under the testing conditions of high oxidation coefficient (2.0), acidity (pH=5.2) and alkalinity (pH=10.05) for 10 h.