THE EFFECTS OF PROCESS PARAMETERS ON ALTERNATING VOLTAGE (AV) PASSIVATION OF 304-STAINLESS-STEEL

In the AV passivation process a potential square wave is applied for a certain length of time at a constant DC bias potential. The effects of the process parameters DC bias potential E(o), pulse length P, pulse amplitude A and ratio R(o) of the duration of the ar,odic to the cathodic portion of the purse on the passive properties of 304 SS have been evaluated using a factorial design experiment. The passive properties have been determined by recording the critical current density i(crit) and the passive current density i(p) as well as the time t(p) for open-circuit potential decay in 0.1 M H2SO4. For E(o) = 300 mV(SCE), P = 100 ms, A = 900 mV and R(o) = 4:1 a reduction of i(crit) by about 200 with respect to the as-received sample has been observed, while i(p) decreased by a factor of 10. A significant increase of t(p) was also noted.