Iron Carbonate Scale Formation and CO₂ Corrosion in the Presence of Acetic Acid Available to Purchase

The role of acetic acid (HAc) on X-65 mild steel carbon dioxide (CO₂) corrosion has been investigated in the presence of iron carbonate scale (FeCO₃). Free HAc is known to be a source of hydrogen ions and to lead to an increase in mild steel corrosion rates, especially at low pH values. Protective iron carbonate scales form at high temperatures (>60°C) and high values of pH. An interesting situation occurs when free HAc and protective FeCO₃ scale co-exist. Numerous studies have looked at HAc and FeCO₃ scale effects separately, but there is little knowledge of how the protectiveness of FeCO₃ scale will be affected, in the presence of acetic acid. Some reports suggested FeCO₃ scale thinning and loss of protection in the presence of HAc Thus in order to clarify this aspect of CO₂ corrosion, the effect of HAc on FeCO.3 scale protectiveness using 3 wt % NaCl salt solution at T = 80°C has been studied under stagnant conditions. No effect of HAc on FeCO₃ scale protectiveness was found over a range of pH and HAc concentrations.