Figure 3

FESEM image of 304 stainless steel treated by EPP through using various applied potentials and intervals: (a) 120 V, 0 s; (b) 120 V, 20 s; (c) 120 V, 40 s; (d) 120 V, 60 s; (e) 120 V, 120 s; (f) 120 V, 180 s; (g) 110 V, 180 s; and (h) 130 V, 180 s.