Corrosion of titanium in supercritical water oxidation environments

Supercritical water oxidation (SCWO) can effectively destroy many kinds of civilian and military wastes, The high temperature and high pressure SCWO operation conditions generate very corrosive environment that many engineering materials fail to withstand. Preliminary test shows that titanium may be a promising material in most of SCWO conditions. Commercially pure titanium is tested in four kinds of SCWO environments. Phenol, sodium dodecyl-benzosulfonate, n-amine phenol, and chlorpyrifos were chosen as typical target pollutants. The results show that titanium is only superficially attacked in the first three SCWO environments while in chlorpyrifos SCWO medium titanium is corroded. The corrosion is temperature dependent, with heavier corrosion occurring at near critical temperature. X-ray diffraction analysis shows that the corrosion products consist of titanium oxy- phosphates and titanium oxide, in which Ti5O4 (PO4)(4) is the main phase.