Abstract
To clarify mechanism of corrosion resistance in outdoor exposure tests for 55% Al-Zn-plated steel sheets, behavior in edge creep development was observed in various cyclic corrosion tests. One of cyclic corrosion tests with a relatively longer highly humid period showed similar corrosion behavior to that of an outdoor exposure test conducted in heavily corrosive area with salt damage. Then, electrochemical impedance of the test panels was measured after the cyclic corrosion tests to control the edge creep development. The edge creep development was strongly depended on the following two factors. One is reaction between an anticorrosive pigment and the substrate where the plating has already dissolved away and the other is electrochemical barrier effect given by tightly adhered coating materials. A schematic diagram indicating the edge creep development was proposed and capability of the corrosion control by the used anticorrosive pigments was discussed with the diagram.
