Comparison of corrosion of nickel and chromium based alloys under conditions of supercritical water oxidation
- Forschungszentrum Karlsruhe (Germany). Inst. fuer Materialforschung
Supercritical water oxidation (SCWO) is a promising and very effective method for the oxidation of organic wastes. Its high volubility for organic compounds and its special physical properties (i.e. density, viscosity) result 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 and Ducrolloy, a new PM Cr-Fe alloy, exposed at 400 bar and 420 C for up to 400 hours in a CH{sub 2}Cl{sub 2}/H{sub 2}O{sub 2} mixture with about 2000 wppm of chloride. The weight losses varied between 5 mg/cm{sup 2} for Ducrolloy and about 175 mg/cm{sup 2} for alloy G-30 after 400 hours of exposure. The kinetic analysis revealed that the weight loss of alloy G-30 followed a linear increase with time, whereas the Cr-base alloy Ducrolloy showed nearly no weight loss up to about 160 hours. After 400 hours in the CH{sub 2}Cl{sub 2}/H{sub 2}O{sub 2}-mixture, the oxide layers formed on both alloys were found to be about 20 {micro}m on Ducrolloy and about 300 {micro}m on alloy G-30. The oxide layer on Ducrolloy was homogeneous and therefore able to protect the alloy against strong SCWO corrosion, whereas a relatively brittle layer, with many cracks, was formed on alloy G-30. Both alloys were preoxidized in air up to 200 hours prior to SCWO exposure. For alloy G-30 nearly no significant effect of the preoxidation on corrosion rate could be stated. On the other hand a reduction of weight loss by a factor of 3 was found for Ducrolloy for short time preoxidation, compared to the not treated material. For both alloys a loss of alloying elements during exposure was obvious. Alloy G-30 lost nickel down to a depth of about 200 {micro}m, whereas Ducrolloy exchanged its iron with the SCWO environment only within a 20 {micro}m zone.
- OSTI ID:
- 696926
- Report Number(s):
- CONF-990401--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Corrosion of high-temperature alloys in chloride-containing supercritical water oxidation systems
Reaction mechanism of preoxidized nickel-chromium-cerium alloy with chlorine gas in the temperature range 400 C to 700 C