Critical Potential of the Corrosion Inhibition of Mild Steel

摘要

The critical potentials (c.p.) for the corrosion inhibition of mild steel in 0.01 M NaCl solns. by the addn. of 0.1 mole/1 of Na benzoate is minus 0.525 v (vs S.C.E.), while the c.p. for the inhibition by NaN0 changes from minus 0.555 to minus 0.620 v as the NaN0 concn. (in an aerated soln.) is increased from 200 to 1600 ppm. The corrosion rate in deaerated solns. was higher than in aerated solns., and the main corrosion product in aerated and deaerated solns. was gamma-Fe 0 and Fe -, resp. The cathodic polarization curves indicate that in spite of being an anodic inhibitor, the NaN0 has a marked effect on the cathodic process, and that the mechanism of the corrosion process involves either 0 depolarization or 0 diffusion; the c.p. corresponds to the point of transition from one mechanism to the other.