Protection of Passive Film Breakdown and Corrosion of Iron in 0.5 M NaCl by Coverage with an Ultrathin Two-Dimensional Polymer Coating and Healing Treatment of Passive Film

Abstract

The time required for passive film breakdown, t_bd and the protective efficiency, P of an ultrathin two-dimensional polymer protective coating prepared by chemical modification of a carboxylate ion self-assembled monolayer adsorbed on a passivated Fe were measured in aerated 0.5 M NaCl. The value of t_bd was short, 1.7 h. The t_bd value of the passivated Fe electrode covered with the polymer coating and further, healed in 0.1 M NaNO₃ was 4.1 h. The P values of these coatings were extremely high, around 99.9% before t_bd, indicating perfect protection of Fe against corrosion in both solutions, unless the passive film was broken down. The P values of protective coatings prepared by chemical modification of three self-assembled monolayers adsorbed on metals and oxidized metals were compared with one another in short and long ranges of the immersion time in oxygenated 0.5 M neutral solutions.