ELECTROCHEMICAL PROPERTIES OF TYPE 304 STAINLESS STEELS PRODUCED BY SEVERAL METHODS

摘要

Three kinds of Type 304 stainless steels: the first one was made by the conventional wrought process (I/M), the second one by conventional powder metallurgy process (P/M) and the third one by Metal Injection Molding process (MIM), were used. The corrosion behavior of these specimens was investigated through the potentiodynamic polarization curve measurement and electrochemical impedance spectroscopy method. In addition, SCC characteristics were also studied. Both the potentiodynamic polarization curve and the Nyquist plot curve of MIM specimen were similar to those of I/M specimen, but different from those of P/M specimens. Therefore it might be suggested that MIM process is quite suitable to improve the corrosion resistance. On the other hand, time constants of P/M and MIM specimens are similar, but they differed remarkably from that of I/M specimen, which is considered to be due to the remained pores in P/M and MIM specimens. Further, it was also confirmed that the SCC was more liable to take place on I/M specimen than MIM specimen.