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  Some manufacturers are concerned with exposed cut-edge on prepainted metal, but research has shown that prepainted cut-edge actually holds up better over time than post-painted surfaces. So make your products a cut above the rest…by using prepaint. The NCCA, with the help of PPG Industries, Inc. and the North American Zinc-Aluminum Coaters Association (NamZAC), compared the corrosion resistance of prepainted with three types of post-paint. Prepainted metal louvers with exposed cut edges were tested in the field along side three sets of metal louvers, one with a post-painted electrocoat, a second with a powder finish and a third with a spray finish. The parts were made of hot dipped galvanized steel, and the louvers were exposed to the same environment over time in Daytona Beach, Florida.
After 16 months, 44 months, and 68 months of exposure to the elements, comparisons showed the corrosion resistance of the prepainted parts was repeatedly and significantly better than the post-painted parts, in terms of the uniformity of treatment and film thickness. The reason the prepainted parts outperformed post-painted ones is that prepainted metal sheet is uniformly cleaned, pretreated and painted as a flat surface, so the edge to edge and side to side variability is virtually eliminated. In addition, the prepainted part has two coats (primer and top coat), and each is tightly bonded to the metal as compared to a post-painted part, which generally has only one coat of paint. In most cases, the prepainted part has paint (one or two coats) on the backside as compared to the post-painted part which at best has a minimal amount of overspray. Uniform pretreatment and paint on the backside of a part increases the corrosion resistance of the part, enhancing long-term durability. So when it comes to cut-edge, prepaint edges out the competition. |
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