Flow-Assisted Corrosion of Carbon Steel in Simulated Nuclear Plant Steam Generator Conditions

Abstract

Flow-assisted corrosion occurs via increased dissolution and/or mechanical degradation of protective oxide formed on the surface of construction materials in direct contact with coolant liquids. In the present paper, this phenomenon is studied on carbon steel in an ammonia-ethanolamine-hydrazine electrolyte by in situ electrochemical impedance spectroscopy in conditions that closely simulate those that prevail in nuclear plant steam generators. Based on the obtained results, a quantitative kinetic model of the process is proposed and parameterized by nonlinear regression of experimental data to the respective transfer function. On the basis of the experimental and calculational results, it is concluded that flow-assisted corrosion of carbon steel is limited by oxide dissolution and cation ejection processes and the protective layer–coolant interface. Expressions for the film growth and corrosion release processes are proposed and successfully compared to operational data.