Corrosion and hydrogen absorption of carbon steels in CO2 environment

The effects of carbon dioxide on corrosion rate, polarization curve and hydrogen content have been investigated for carbon steels in acetate solutions and sodium carbonate solution with a pH range of 2 to 9 at 313 K under carbon dioxide and nitrogen atmospheres. In the acidic solutions less than pH4 both general corrosion and hydrogen content are accelerated by the existence of carbon dioxide. In the solutions more than pH7 little corrosion is observed with or without carbon dioxide, where as hydrogen content is detected only at the existence of carbon dioxide. The anodic and cathodic polarization curves with or without carbon dioxide show that their reaction overpotentials are affected by carbon dioxide, effect of which changes depending upon pH. The results obtained are qualitatively explained in terms of the formation of iron carbonate, the adsorption of carbonate ions and so on. (author)