Characterization of oxide layers formed on type 316 stainless steel exposed to the simulated PWR primary water environment with varying dissolved hydrogen and zinc concentrations

Abstract

The effect of dissolved hydrogen (DH) content and zinc addition on the corrosion behavior of type 316 stainless steel was investigated in the primary water environment of pressurized water reactors. The coupled effect, as well as the individual effect of increasing DH concentration and zinc addition, was investigated. Increasing DH from 25 (normal) to 50 (high) cc/kg-H2O resulted in 3 times thicker oxide layer. With the addition of 30 ppb zinc, the oxide layer became substantially thinner in both normal and high DH conditions. The measured electrochemical properties of oxide layers were in agreement with the observed corrosion behavior such that the zinc incorporated oxide film showed significant increase in reaction resistance and bode impedance value. Meanwhile, both reaction resistance and bode impedance slightly decreased with increasing DH concentration. Overall, the best corrosion resistance was observed in the simulated PWR environment with normal DH concentration and zinc addition. (C) 2021 Elsevier B.V. All rights reserved.