Abstract
The deterioration of the coated steels is defined as the combing and synergistic effects of the degradation of surface coating film by ultraviolet ray and heat, and the corrosion of underneath steels by water and salt. For the evaluation of the deterioration process of the coated steels, the cyclic-weathering test apparatus was newly designed combining salt spray, ultraviolet ray irradiation of metal-halide lamp and conditioning under a moisture atmosphere. Five types of polyvinyl chloride-resin coated steels were weathered to the cyclic-weathering in the test apparatus, and the surface appearances and the changes of some properties were measured for comparison with those of the outdoor exposed samples. The cyclic test combining salt spray for 2 hours, ultraviolet ray irradiation of metal-halide lamp for 16 hours and conditioning under moisture for 2 hours was shown to cause the deterioration of the coated steels highly similar to those of outdoor exposed ones. Moreover, it was recognized that appearance, color difference, gloss and adhesive strength are relevant to the evaluation of the deterioration of coated steels.
