Electrochemical Impedance Spectroscopy of Corrosion of 16MnR in Circulating Water of Refinery

The main influencing factors including chloride ion concentration, water temperature, pH value and calcium ion concentration on corrosion of materials in circulating water system were examined. The electrochemical impedance measurements of 16MnR were conducted with electrochemical test system and then the equivalent circuit Rs(CtRP) was adopted to fit the experimental impedance curves. Orthogonal tests were arranged and the sequence of contributions from each factor to the corrosion of 16MnR was obtained. The results showed that the impedance profile of 16MnR in the circulating water showed a single capacitive resistance arc. The parameters controlling the corrosion process included the resistance of charge transfer RP and the impedance value increased with the increase of RP, indicating slowing down of the corrosion rate of 16MnR. The most important impacts on 16MnR corrosion were chloride ions and temperature.