Supercritical water oxidation (SCWO) is a promising and very effective method for the oxidation of organic wastes. Its high volubility for organic compounds end ita 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 orgenics, a severe corrosion attack of most of the materials has been observed. This paper describes the results of investigations of high
temperature alloys like alloy No. 214, alloy 602 CA, G-30 alloy alloy 625 end alloy 686, exposed at 400 bar and 420”C for 24 hours in a CH2CQT1202 mixture with about 2000 wppm of chloride. The weight losses of all, samples varied between 3 mg/cm2 for G-30 alloy and about 73 mg/cm2 for alloy 686. The alloy
No. 214 showed an increased corrosion for the preoxidized material, whereas the corrosion rate of alloy 602 CA was reduced by a factor of 3 due to the preoxidation at 900°C, prior to SCWO-exposure. The post mortem analysis revealed that alloy 686 has lost most of its nickel down to a depth of about 150 pm. The G-30 alloy showed a good corrosion behavior because of the formation of a protective oxide layer during the exposure. The layer was homogeneous with a thickness of
about 12 pm, but a slight nickel leaching was observed, too. Keywords: SCWO, supercritical water, corrosion, oxidation, hydrochloric acid, high temperature, high pressure, nickel base alloys