Corrosion Characteristics of SUS304 Stainless Steel Produced by SPS Process through Electrochemical Method

The corrosion behavior of SUS304 specimen produced by spark plasma sintering (SPS) has been studied through electrochemical tests such as polarization curve measurement, electrochemical reactivation ratio measurement and electrochemical impedance spectroscopy (EIS), compared to those of specimens produced by the conventional ingot metallurgy process (I/M) and the powder metallurgy process (P/M).The corrosion current density (icorr) of the SPS specimen has a tendency increasing with a decrease in electrochemical corrosion potential (Ecorr). The corrosion resistant of the SPS specimen was inferior to that of the I/M specimen because of carbon diffusion from a graphite punch rod while it was improved by removing the surface file through polishing.The electrochemical reactivation ratio of the SPS specimen without polishing was 27.4%, which was significantly higher compared to 0.13% for the I/M specimen because of its poor passivation film.The Rct value of the SPS specimen without polishing was 0.09 times as large as that of the I/M specimen, while it became 0.63 times for the SPS specimen with polishing. This result well agrees with the icorr value obtained by the electrochemical polarization test.