Corrosion of Nickel Based Alloy G-30 between 100 and 420°C, pH Values from 2 to 6 and Pressures Ranging from 250 to 480 Bar under Conditions of Supercritical Water Oxidation Available to Purchase

Supercritical water oxidation (SCWO) is a promising and very effective method for the oxidation of organic wastes. Its high solubility for organic compounds and its special physical properties (i.e. density, viscosity) resulting in a key advantage over standard processes like incineration. Due to the formation of HCl during oxidation of chlorine organics, a severe corrosion attack of most of the materials has been observed. This paper describes the results of investigations of nickel base alloy G-30, exposed at pH values from 2 to 6, temperatures ranging from 100-420°C and pressures between 250 and 480 bar at duration’s of 120 hours in a CH₂Cl₂/H₂O₂- respectively NaCl/H₂O₂-mixture with about 2000 wppm of chloride.

The weight losses varied between a few and 200 mg/cm², depending on the environmental conditions during the tests. The corrosion attack in the subcritical region increased at pH 6 with increasing pressure in the temperature range between 150 and 250°C. The maximum of the metal loss was nearly independent of pressure at around 250°C. With increasing temperature, especially in the supercritical fluids, a reduced attack was found for high pressures, whereas for 250 bar a strong increase was obvious. At a pH of about 2, the corrosion attack increased with decreasing pressure between 100 and 380°C. Above the critical point, a reversed behavior was found i.e., the corrosion attack increased with increasing pressure or density of the fluid.