2004 Volume 53 Issue 6 Pages 322-328
Supercritical water (SCW) process is an effective method for the destruction of hazardous organic wastes and the upgrading of unused hydrocarbon resources. However, the corrosion of a reactor and a heat exchanger is known as the major drawbacks to industry application. So it is important to select corrosion-resistant materials and explicate the life span of those under SCW state. The objectives of this study are to evaluate corrosion rate of corrosion-resistant materials and to explicate corrosion mechanism under SCW and reducing environment.
(1) The oxide layer of Cr-Mo steel is sensitive to environment condition, for example oxygen-hydrogen pressure, anion concentration.
(2) Corrosion rate of SUS316 is little in SCW. Corrosion rate in SCW with the addition of NaCl or HCl is high, especially corrosion rate in sub-critical condition and low pH (under pH2) is remarkably high. It is difficult to apply SUS316 to equipment material in these environments.
(3) Corrosion rate of Ni-base alloy is lower than that of SUS316. Ni-45Cr-1Mo (MC Alloy) containing much chromium is the most corrosion-resistant in SCW. Ni-base alloys, for example MAT21 or Hastelloy C-276, containing the moderate content of elements as Cr and Mo are more stable under reducing environment.
