Abstract
Materials used for this experiment were three kinds of Type 304 stainless steels: the first one was made by the conventional wrought process (I/M), the second one was made by conventional powder metallurgy process (P/M) and the third one was made by Metal Injection Molding process (MIM). Using these three stainless steel specimens the corrosion behavior of them were investigated in the aqueous solution (2.5 kmol/m3H2SO4+0.2 kmol/m3NaCl) through potentiodynamic polarization curve measurement and electrochemical impedance spectroscopy (EIS). In EIS measurement, a natural electrode potential with perturbation AC potential, amplitude of which was 10 mV was applied to the specimen, and analyzing frequency range was from 100 kHz to 1 mHz. Both the potentiodynamic polarization curve and the Nyquist plot curve of MIM specimen were similar to I/M specimen. These curves of P/M specimens were differed greatly from those of MIM and I/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.
