Effects of nitrogen ion implantation on the corrosion characteristics of Cu-electroless plated and sintered stainless steel

Electrochemical tests were used to investigate the effects of N-2(+) implan tation on the corrosion characteristics of Cu-electroless plated and sinter ed stainless steel (SSS) in H2SO4, H2SO4 + KSCN, and HCl solutions. Stainle ss-steel compacts containing Cu (2-10 wt%) were prepared using the electrol ess Cu-plating (ELCP) method. N-2(+) implantation was carried out using N-2 gas as the ion source of the feed materials. The ions were embedded by an accelerator with an energy of 130 keV to a dose of 3.0 x 10(17) ions cm(-2) on the SSS at 25 degrees C in a 2 x 10(-5) Torr vacuum. In the case of N-2 (+) implanted 316LSSS, the corrosion potential increased, and the passive c urrent density decreased. As the Cu content increased, the corrosion potent ial of N-2(+) implanted 316LSSS drastically increased, with the exception o f a slight decrease in the passive current density. The reactivation peak o f N-2(+) implanted and unimplanted SSS did not appear (not sensitized), but the activation current density decreased. The pitting potential of N-2(+) implanted 316LSSS was higher than that of the implanted 304LSSS due to the synergistic effect of Mo and N, and the inhibition of NH4+ against Cl-. The pitting resistance increased as the Cu content increased, due to the forma tion of CuCl2 . 3Cu(OH)(2), CuO and Cu2O on the surface. (C) 1999 Elsevier Science S.A. All rights reserved.