937920.fig.003a
(a)
937920.fig.003b
(b)
937920.fig.003c
(c)
Figure 3: Potentiodynamic polarization curves of steel immersed in aerated 0.1 mol L−1 Na2SO4 solution (pH 6.0) in the presence of tannin (1) and absence of tannin (2) for (a) 1 day, (b) 3 days, and 7 days.