A variety of electrochemical techniques has been used for the evaluation of protective performance of coated steel. For example, one of them is electrochemical impedance spectroscopy. (EIS) Each method has its own characteristic and is suitable to determine some kinds of anti-corrosive mechanisms of coating film. We developed a new evaluation method of protective coatings using current interrupter technique.

Generally the equivalent circuit of coated steel is simplified as a connection of the resistance of test solution, the impedance of paint film and impedance of mild steel surface in series. When the time constant of the paint film is much smaller and very different from that of the metal substrate as coated steel in general, the two equivalent circuits can be separated from each other.

Thus the polarization resistance of metal substrate was determined by separating the measured paint film impedance from the metal substrate impedance.

Electrochemical parameters can be measured by using current interrupter technique.

Results of protective coating performance obtained by some experiment were discussed.

Subject
Circuits, Films, Coated steel, Coating performance, Capacitance, Constants, Sodium chloride solution, Electrochemical current, Film thickness, Rust, Polarization resistance, Alkyds, Paints
Keywords:
Current interrupter technique, coating, under-film corrosion tester, electrochemical method, polarization resistance, coated steel
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2010
Association for Materials Protection and Performance (AMPP)
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