2003 Volume 52 Issue 8 Pages 421-427
Conductive polymer film of polypyrrole (PPy) doped by polymolybdate (PMo) anions was prepared on mild steels by anodic polymerization for corrosion prevention of the steels. The PPy-PMo conductive film prepared exhibits good adherence to the steel substrate. The mass and thickness of the PPy-PMo film linearly increase with electricity during constant current polymerization at 5mA·cm-2. The density of the PPy-PMo polymer film was evaluated to be 2.5g·cm-3 from the ratio of the mass to thickness. A corrosion test in neutral and acidic 3.5wt% NaCl solutions was done for the steels covered by the PPy-PMo film. Corrosion of the steels is suppressed by the films: the corrosion rate in the neutral solution decreases by 1/3 compared with that of the bare steel and the rate in the acidic solution by 1/4. The film was gradually reduced during immersion in the solutions with progress of the corrosion reaction of Fe dissolution to Fe2+, which is accompanied with the dissolution from PMo in the film to MoO42- in the neutral solution, or with pickup of protons and sodium ions in the acidic solution.