Effect of dissolved hydrogen on the electrochemical behaviour of Alloy 600 in simulated PWR primary water at 290 °C

With an increase in dissolved hydrogen (DH) content from 0 to 5 cm³ STP H₂/kg H₂O the electrochemical behaviour of Alloy 600 in deaerated PWR primary water at 290 °C was investigated, using corrosion potential (E_corr) monitoring, potentiodynamic polarization, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). DH content controls the E_corr of Alloy 600. Raising DH content directly promotes the cathodic process and reduces the passivity of Alloy 600 significantly. EIS results show that increasing DH content results in a thinner inner-layer oxide film and ions diffusion becomes easier. The mechanism of these DH effects is discussed.