EIS OF DUPLEX STAINLESS STEEL IN FLOWING CORROSIVE MEDIA

The electrochemical impedance spectroscopy(EIS)of duplex stainless steel in flowing chloride solution was measured. It was found that EIS of duplex stainless steel in flowing single phase media is a capacitive loop with a larger diameter when flow velocity is below the critical value, but EIS of duplex stainless steel is composed of two capacitive loops once flow velocity is above the critical value. If corrosive media contains solid particles, EIS of duplex stainless steel consists of a capacitive loop in high frequency range and a straight line in low frequency range when flow velocity is lower than critical value. However, an inductive component was observed on impedance plane and the shrinkage of the real part of impedance was also seen in low frequency range though EIS of duplex stainless steel is only a capacitive loop when flow velocity is higher than critical value. Electrode reaction kinetics model of duplex stainless steel in flowing chloride solution was found on the basis of electrochemical corrosion theory, which was used to explain EIS of duplex stainless steel in flowing chloride solution. The dominant role of electrochemical corrosion in the process of flow-induced corrosion of duplex stainless steel electrode in flowing chloride solution was further understood.