In situ Raman spectroscopic investigation of zirconium-niobium alloy corrosion under hydrothermal conditions

In situ Raman spectroscopy was employed to investigate corrosion of a zirconium-niobium alloy in air-saturated water at a pressure of 15.5 MPa and temperatures ranging from 22 to 407 deg. C in an optically accessible flow cell. Monoclinic ZrO2 (m-ZrO2) was identified under all conditions after the coupon was heated to 255 deg. C for 19 h. Cubic ZrO2 (c-ZrO2) was tentatively identified in situ during heating at temperatures between 306 and 407 deg. C, but was not observed under any other conditions. Species tentatively identified as α-CrOOH and a CrVI and/or CrIII/CrVI compound were observed in situ during heating at temperatures between 255 and 407 deg. C, but were not observed under any other conditions. The chromium compounds were identified as corrosion products released from the optical cell and/or flow system