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

In situ Raman spectroscopy was employed to investigate corrosion of a zirco nium-niobium alloy in air-saturated water at a pressure of 15.5 MPa and tem peratures ranging from 22 to 407 degreesC in an optically accessible flow c ell. Monoclinic ZrO2 (m-ZrO2) was identified under all conditions after the coupon was heated to 255 degreesC for 19 h. Cubic ZrO2 (c-ZrO2) was tentat ively identified in situ during heating at temperatures between 306 and 407 degreesC, but was not observed under any other conditions. Species tentati vely identified as alpha -CrOOH and a Cr-VI and/or Cr-III/Cr-VI compound we re observed in situ during heating at temperatures between 255 and 407 degr eesC but were not observed under any other conditions. The chromium compoun ds were identified as corrosion products released from the optical cell and /or flow system. Published by Elsevier Science B.V.