Abstract
Laboratory studies of perforation corrosion on automotive materials are described, in which a perforation coupon simulated a crevice on a car body. Electrochemical impedance spectroscopy was used to determine in situ the corrosion rate of precoated steel sheet in a particular crevice geometry. Measurements were taken during an accelerated cyclic laboratory test, while visual inspections and microscopic examinations of corrosion attack were performed at the end of the exposure. The results show that the crevice width (the distance between the two sides of the crevice) has a significant influence on the corrosion performance of coil coated steel. High corrosion rates were observed during the first stage of the drying period. The degree of wetness inside the crevice was monitored during the wet-dry cycle by measurements of the galvanic current flowing between a gold electrode and the coil coated steel. Results of galvanic current measurements in crevices with different widths may provide an explanation for the corrosion performance of coil coated steel as a function of crevice width.
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