Flow, chloride, and pH effects on carbon steel corrosion in BWR cold shutdown: Development of a 4-STEP corrosion model

The corrosion behavior of carbon steel in Boiling Water Reactor (BWR) plants during cold shutdown was investigated under flow velocities of 0.1 and 2.0 m/s, chloride ion (Cl - ) concentrations of 0.01, 0.1, 1, and 10 mg/L, and pH of 6.3, 7.6, and 8.5. Experiments over 800 h demonstrated that a high flow velocity (2.0 m/s) promotes rapid passivation , while a low flow velocity (0.1 m/s) results in sustained corrosion. Cl - damaged protective films, accelerating corrosion, particularly under high flow velocity. Higher pH and/or electric conductivity increased uniform corrosion . The newly developed 4-STEP corrosion model successfully reproduced the experimental results. • Carbon steel corrosion was studied under varied flow, Cl - , and pH. • High flow velocity promoted rapid passivation, reducing the uniform corrosion rate. • Cl⁻ damaged protective films, accelerating corrosion under high flow velocity. • Higher pH and/or electric conductivity increased uniform corrosion. • The developed corrosion model successfully reproduced the experimental results.