Experimental Study of Metal Corrosion in Supercritical Brines: Application to Supercritical Water Oxidation of Hazardous Wastes

摘要

The corrosion behavior of Hastelloy C, ticanium, zirconium, niobium, tantalum, and gold have been studied as a function of temperature (200 degrees - 4000 degrees C), acid concentration (0 0.02 mol/Kg), oxygen content (0.1-1 mol %) and NaCi content (0-0.2 mol/Kg). The intent of these experiments was to determine an empirical rate law for corrosion of these metals as a function of the parameters listed above. Due to the complexity of the corrosion behavior of these metals and the different responses of different metals, rate law determination was not possible. However, our results qualitatively indicate that Nb and Zr are not suitable for service under SCWO conditions, for they rapidly convert to oxides which erode into the fluid. Ti proved resistant to dissolution into the fluids, but was subject to pitting corrosion. Au was subject to galvanic effects, which increased its dissolution rate. This suggests that gold would not be suitable for use with other metals in a SCWO system. Stainless steel and Hastelloy C displayed fairly rapid corrosion, with Ni and Mn preferentially dissolving out of the metal and Cr and Mo remaining begin Tantalum proved to be the most resistant metal tested, and is an excellent candidate for possible long-term use under.