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Abstract
In order to improve the accuracy of electrochemical corrosion potential (ECP) calculations, information about the effects of the flow velocity, the type of oxidization species, the oxide film thickness, and the oxide film classification on the polarization curve is needed. Polarization curve measurements were studied here with that information goal in mind. A wire-shaped working electrode was employed to remove the IR drop caused by high solution resistance, which makes it difficult to apply a proper potential to the working electrode. In order to measure the static state current, the potential scanning condition was optimized.It was confirmed that a steady-state current can be measured by establishing a potential scanning rate for applying a potential not greater than 0.01mV.s−1 with a step-shaped waveform. This method was employed to measure the anodic polarization curve of type 304 stainless steel in deaerated 553K high-purity water. The passivation behavior was clearly observed. Also, the cathodic polarization curves in water containing dissolved oxygen of less than 1000 ppb were measured. The oxygen concentration dependence of ECP was calculated from measured polarization curves. The ECPs calculated using the measured polarization curves were in good agreement with those measured with an electrometer, confirming the validity of the measured polarization curves.
