Corrosion of 316 Stainless Steel Tubing in Ammoniacal Sulfate Solution at Supercritical Temperatures and Pressures

A bench-top supercritical water reactor was constructed for the purposes of conducting corrosion and fouling experiments.  The reactor’s austenitic 316 stainless steel tubing was exposed to ammoniacal ammonium sulfate solution under supercritical water oxidation conditions to a maximum temperature of 420°C at 3500 psi.  Despite an initial pH of 10 at 25°C, the ammoniacal solution led to severe alloy degradation within less than 40 minutes of exposure.  The reactor tubing was sectioned and the corrosion morphology was analyzed.  The results of the morphological analysis are compared to effluent analyses.