Cathodic reaction mechanisms in CO₂ corrosion of low-Cr steels

Abstract

The cathodic reaction mechanisms in CO₂ corrosion of low-Cr steels were investigated by potentiodynamic polarization and galvanostatic measurements. Distinct but different dominant cathodic reactions were observed at different pH levels. At the higher pH level (pH > ~5), H₂CO₃ reduction was the dominant cathodic reaction. The reaction was under activation control. At the lower pH level (pH < ~3.5), H⁺ reduction became the dominant one and the reaction was under diffusion control. In the intermediate area, there was a transition region leading from one cathodic reaction to another. The measured electrochemical impedance spectrum corresponded to the proposed cathodic reaction mechanisms.

Keywords

low alloy steel / carbon dioxide corrosion / EIS / cathodic reaction / mechanisms

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