An electrochemical study on the effect of bicarbonate ion on the corrosion behaviour of carbon steel in CO2 saturated NaCl solutions

Abstract

The electrochemical study on the effect of HCO3− on the corrosion behaviour of carbon steel in CO2 saturated NaCl solutions was investigated through mathematical calculation of impedance plots and potentiodynamic polarization. Results reveal that a competitive adsorption between HCO3−/Cl− exists, and HCO3− is able to reduce and/or replace the adsorption of Cl− on carbon steel surfaces with the elevation of HCO3− concentration. In addition, at the certain condition (CO2-saturated solution containing 0.1 M Cl−), carbon steel tends to passivate when HCO3− concentration reaches 0.5 M. However, pitting can be triggered in 0.2 M HCO3− concentration. The findings of this work spot light on the understanding of many parameters related to this process, which is of great significance to prevent the underlying corrosion failure and prolong the lifespan of carbon steel pipelines in the service environment.