EDGE CREEP OF PREPAINTED ZN-55-PERCENT-AL COATED STEEL SHEET

The effects of pretreatments and paint coatings on the edge creep performance of prepainted Galvalume were studied by means of salt spray test and outdoor exposure test. Edge creep progress behavior in salt spray test was different from that in outdoor exposure test. According to the results of outdoor exposure test for up to 10 years, the edge creep of prepainted Galvalume is more appreciable than that of the prepainted galvanized steel sheet in the early stages of exposure. However, the edge creep rate of prepainted Galvalume decreases with the lapse of time while that of prepainted galvanized steel sheet is kept almost constant. As the results, edge creep width becomes larger in galvanized steel sheet than in Galvalume in 7 to 9 years of exposure. Meanwhile in salt spray test, edge creep width of prepainted galvanized steel sheet does not exceed that of prepainted Galvalume up to 1 000 h of exposure. Effects of pretreatments and coatings were not clearly noticed except that special primer for Galvalume decreased edge creep width of prepainted Galvalume in salt spray test.