An investigation of corrosion mechanisms of constructional alloys in supercritical water oxidation (SCWO) systems

Supercritical water oxidation (SCWO) is a technology that can effectively destroy aqueous organic waste above the critical point of pure water. These waste feed streams are very aggressive and pose material performance issues. As potential alloys in construction of SCWO systems, nickel-base alloys are tested. Corrosion in aqueous feed streams of ambient pH values of 2, 1 and 7 is studied both at supercritical (-425⁰C) and subcritical (-300-360⁰C) temperatures with a constant pressure of 24.1MPa. Dealloying of Ni and Fe, and oxidation of Cr and Mo are observed at subcritical temperatures at a pH value of 2. At a pH value of 1, even chromium is selectively dissolved and only molybdenum forms a stable oxide at the subcritical temperature. At supercritical temperatures, normal thin oxidation occurs at both pH values of pH 2 and 7. In contrast, in the neutral pH solution, dealloying is not observed at any temperature. Stress corrosion cracking (SCC) in acidic feed streams is observed both at the supercritical and subcritical temperatures. In order to understand the corrosion mechanisms, the chemistry of a feed stream, the formation of the dealloyed oxide layer, and the level of stress are investigated.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Kim, Hojong, 1974-

Advisor dc:contributor.advisor

• Ronald M. Latanision and Ronald G. Ballinger.

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/16636

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/16636