2016 Volume 65 Issue 10 Pages 420-424
An ultrathin two-dimensional polymer coating was prepared on a passivated iron electrode and then the passive film was healed by immersion treatment in 0.1 M NaNO3. The time required for passive film breakdown, tbd was measured by monitoring the open-circuit potential in 0.1 M solutions of four anions. The protective efficiencies of the passivated, polymer-coated and healed electrodes were extremely high, around 99.9% before tbd and hence, complete protection against corrosion of iron was accomplished, unless the passive film was broken down. On the other hand, the tbd values of the passivated Fe electrode, tbd0 have been determined in 0.1 M solutions of 14 different anions. In the present investigation, the tbd values of the passivated electrode covered with the polymer coating, tbd1 and those of the passivated, polymer-coated and healed electrode, tbd2 are estimated from tbd0. These values are discussed using classifications of anions based on the hard and soft acids and bases principle. Further, the effect of anion concentration on the tbd2 value is discussed.