Electrochemical screening of organic inhibitors for corrosion of UNS N0400 in saturated monoethanolamine solution

Abstract

In response to environmental concerns associated with the buildup of arsenic sludge used in the monoethanolamine (MEA) CO₂ removal unit at a refinery in Kuwait, two organic based inhibitors have been evaluated as potential replacements for the inorganic sodium arsenate used earlier. The inhibitors were evaluated for UNS N0400 (Monel 400) in fresh MEA solution saturated with an 85H₂–15CO₂ gas mixture at 40°C using electrochemical impedance spectroscopy, potentiodynamic polarisation, and weight loss techniques. Interfacial impedance data obtained at low frequencies were marginally higher when the two organic inhibitors were added. The percentage efficiency obtained by the potentiodynamic method was 66% for an amide based inhibitor and 15% for an amine based inhibitor. Weight loss data also indicated that the corrosion rate of N0400 in the MEA solution with the amide based inhibitor was lower than that with the amine based inhibitor.