The mechanism of abnormal corrosive behavior of metallic materials in the pseudocritical region of supercritical water

To study the corrosive behavior of metal materials in the pseudocritical region of supercritical fluid and explain the abnormal mechanism in corrosive within the pseudocritical region, a corrosive experimental platform for supercritical fluids was built. Three different candidate materials for Supercritical Water Reactor (i.e. Q235 low carbon steel, 316 L austenite stainless steel and 3Cr13 martensitic steel) were selected and reacted for 200 h in the pseudocritical region (375.6 ℃, 22.5 MPa) and gas-like region (405.6 ℃, 22.5 MPa) respectively. The results show that 316 L exhibits abnormal corrosive exacerbation in the pseudocritical region with a corrosive rate 1.67 times that of the gas-like region. Considering the special variation of physical properties in pseudocritical region, the enhanced kinetic effect is further analyzed. It is found that the migration of corrosive media such as oxygen to the material matrix is accelerated, which aggravates the corrosive products shedding and freeing. The present study can provide a basis for improving the anti-corrosive performance of materials under supercritical fluid environments and providing a safe operation of the Supercritical Water Reactor.