Influence of cerium (III) ions on corrosion and hydrogen evolution of carbon steel in acid solutions

This paper intended to investigate the influence of rare earth Ce(III) ions on the corrosion behavior of carbon steel in two acid solutions (0.5 M HCl and 0.25 M H2SO4) in order to control the rate of hydrogen evolution in those systems. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used for corrosion rate and electrochemical impedance evaluation. SEM was used to examine the sample surfaces immersed in acid solutions containing the optimal threshold Ce(III) concentration (0.1 mM). All results reveal that the corrosion resistance of carbon steel in HCl is superior to that in H2SO4 due to the higher rate of hydrogen production in the latter. A model for the corrosion process mechanism and inhibition by Ce(III) salt for carbon steel in the two tested media is proposed.

► 0.5 M HCl and 0.25 M H2SO4 media were used for studying C-steel corrosion and HER.
► Ce(III) inhibits corrosion up to 0.01 mM and stimulates the process with overdoses.
► Film resistance (Rp) increases with Ce3+ addition and decreases with temperature.
►  Activation energy in HCl is higher than in H2SO4 either devoid or containing Ce3+.
► Ce performance is superior in HCl than in H2SO4 as it stabilizes the steel surface.