Table 5: Polarization parameters for the corrosion of carbon steel immersed in 0.1 mol L−1 Na2SO4 solution (pH 2.5), in the presence and absence of tannin, for different periods.

𝑗 c o r r (μA cm−2) 𝐸 c o r r (V) 𝑅 𝑝 (Ω cm2)IE (%)

1 day103.4−0.65202.7655.7
1 day with tannin25.90−0.60457.58
3 days123.73−0.6876.86362.0
3 days with tannin25.93−0.63202.23
7 days122.90−0.6868.15268.7
7 days with tannin29.20−0.63217.72