Corrosion behavior of carbon steel in methyldiethanolamine(MDEA) solution was investigated by Electrochemical Impedance Spectroscopy(EIS).The results were showed that the corrosion rate of carbon steel in solution containing dissolved oxygen is higher than that in solution removed of dissolved oxygen before cathodic activation.They were reversed after cathodic activation.The corrosion rate is increased at first and then decreased when the concentration of MDEA is increased in the blank solutions.In the simulated solutions containing quantities of!heat-stable salts(HSS),the corrosion rate is decreased monotonously with increase of the MDEA concentration.As anodic polarization potential is increased,the EIS of carbon steel in HSS simulated solution showed characteristics of inductive shrinkage,negative impedance and Warburg-response,which implied pitting corrosion,transition from active state to passive state and passive state,respectively.The rate of cathodic reduction is determined by both electrochemical reaction and diffusion process.The rate-determining step of the anodic dissolution is electrochemical reaction.


heat-stable salts, methyldiethanolamine, electrochemical impedance spectroscopy, carbon steel, corrosion

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