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Improvements to the Coil-Coating Process Continue to Flow

Published: Paint & Coatings Industry (PCI)

Constant improvements to the coil-coating process are why prepainted metals are becoming manufacturers’ go-to method. Manufacturers have discovered that today’s prepainted metals offer more cost-savings, durability and specialized coatings than ever.

One of the most appreciable advantages is the energy savings the coil-coating process affords. The energy used to cure coil-coated metal is substantially less than other processes. Savings are achieved by using high-speed material processing and by recycling 90 percent or more of the painted coil’s VOCs back into the curing ovens, where they are re-used as fuel. Major improvements to the curing ovens, the most energy- intensive part of the coil coating process, enable paint to cure in just seconds, using innovative induction, infrared and near-infrared curing.

Because pre-painting does not require manufacturers to store paint at their facility, it also effectively eliminates all the costly labor and environmental challenges related to post- painting (e.g. waste removal, emission control and assorted EPA compliances). Modern coil-coating facilities already have approved water and air pollution equipment in place that satisfies EPA requirements. Many coil-coating lines have also substantially reduced water usage by using innovative, no-rinse pre-treatments. These savings all add up for manufacturers.

In addition to the cost savings, prepainting provides a superior finish. That’s because a flat sheet enables excellent control of coating weights of both the pretreatment and the paint to within a tenth of a mil or less, depending upon the equipment and the paint system being applied. Prepainting also allows more design options. Prepainted coils can be printed, striped and embossed to create special visual effects. In many ways, coil coating has limitless design possibilities, most of which are virtually impossible with other systems.

Since prepainting allows metals to be finished in one continuous pass, there’s also flexibility in how the metal is coated and the types of coatings that can be used. Organics and inorganics, such as polyesters, epoxies, vinyls, plastisols, acrylics, water-born emulsions, fluorocarbons, dry lubricants, treatment and primer combinations, can all be applied. This allows you to select the most appropriate coating for your part application—from abrasion resistance, weathering performance, durability, hardness and more, prepainting offers limitless options.

One of the main reasons for buying prepainted product is to provide a specific color appearance. Often the customer is matching the prepainted part to other components of a building or product. Matching the color standard is critical for good appearance of the final assembled product. For repeat colors, matching the standard on each run ensures that there will be consistency of color over time. Many factors can affect color: paint formulation and quality, film thickness, substrate color, cure temperature (PMT) and dwell time in curing ovens. These can all be monitored and closely inspected during the prepaint process assuring perfect color appearance and matching.

Prepainted surfaces not only look great, research has proven that prepainted surfaces actually hold up better over time. The NCCA, with the help of PPG Industries, Inc. and the North American Zinc-Aluminum Coaters Association (NamZAC), compared the corrosion resistance of prepaint with three types of post-paint. Prepainted metal louvers with exposed, cut edges were field-tested alongside 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. The louvers were exposed to the same environment 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 significantly better in terms of the uniformity of treatment and film thickness.

The list of prepainting superlatives is lengthy: energy and labor savings, reduced environmental risks, outstanding appearance, more design options, superior color matching, better wear and corrosion resistance, to name just a few. To learn more about improvements happening in the coil coating industry, be sure to visit today.