937920.fig.009a
(a)
937920.fig.009b
(b)
Figure 9: Bode plots for steel immersed in 0.1 mol L−1 Na2SO4 solution (pH 2.5) for 1 day (closed triangle), 3 days (closed circle), and 7 days (closed star) in the presence of tannin; for 1 day (open square), 3 days (open lozenge), and 7 days (open circle) in the absence of tannin.