CONSTITUTION OF PAINT FILM

摘要

PURPOSE:To enhance the edge corrosion resistance of a steel plate and the sharpness of top coat painting by applying top coat wherein the curing start time of a paint film calculated by measuring the logarithmic attenuation factor thereof is 15 - 20min to an electrodeposition film having a specific surface. CONSTITUTION:In order to enhance edge corrosion resistance, the center line mean roughness Ra of the roughness curve measured at a cut-off wavelength of 0.8mm of an electrodeposition painting surface is prescribed to 0.3mum or more and, from the finish properties due to top coat, Ra of the electrodeposition painting surface is prescribed to 0.8mum at the max. and the sum SIGMAP0.5mm > of power spectrum values at a wavelength of 0.5mm or less by surface frequency analysis is prescribed to 80muV<2> or less. Ra is prescribed to 0.8mum or less at the max. because the smoothing of the roughness up to 0.3mum of the electrodeposition painting surface is possible in the case of intermediate coat whose curing start time is 12 - 15min corresponding to Ra of the electrodeposition painting surface and the curing start time measured according to an OPA method and the smoothing of roughness up to Ra of 0.8mum is possible in the case of intermediate coat of 15 - 20min. Further, SIGMAP0.5mm > is prescribed to 80muV<2> or less because smoothing is possible at 80muV<2> or less in the case of the intermediate coat of 15 - 20min in the same way as Ra and roughness equal to or more than 80muV<2> can not be smoothed fundamentally by the intermediate coating.