Corrosion Inhibition of Carbon Steel in SULFIRAN® Process

In this investigation, attempts were directed to study the inhibitive effects of nitrite and phosphate base inhibitors for the carbon steel alloy samples, which are used in an acid gas treatment process (The SULFIRAN® solution), in Fe-EDTA solution. Electrochemical techniques, i.e. polarization curves and electrochemical impedance spectroscopy (EIS), were used to evaluate the inhibition efficiency. Linear polarization resistance (LPR) and weight loss techniques were also used to determine the corrosion rate for the pilot tests. The results indicated that adding inhibitors reduced corrosion rate to some suitable values (<5 mils per year (mpy)). For both inhibitors, the inhibition efficiency increased with the inhibitor concentration. The results showed that the inhibition efficiency of the phosphate base inhibitor was less than the nitrite base inhibitor.