With Prepainted Metal, Products Last Longer And The Environment Stays Greener
By Jim Dockey, National Coil Coating Association
While there are many benefits to using prepainted metal in terms of cost savings and production line efficiencies, many manufacturers choose coil coated metal for its durability. Prepainted metal provides products with increased performance and corrosion protection, helping coatings last longer, look better and end up in landfills less often. That’s a win for us all.
In the metal construction industry, prepainted metal is the de facto standard for metal roof and wall panel systems specified with a painted finish. And beyond metal cladding systems, prepainted metal is routinely used for HVAC units, truck trailers, bleachers, road signs, fuel tanks, exterior doors, window frames and metal furniture. Coil coated metal is used for these products because it provides the utmost protection from the elements.
Even when the same type of coating is used, prepainted metal parts outperform post-painted parts due to the application process. When the coil coating process is used, the metal is uniformly cleaned, primed, pretreated and painted as a flat surface on both sides before it is formed into parts. A primer coat is often used and prevents the undercutting of paint and enhances corrosion resistance, durability of the product, and overall quality. Furthermore, with prepainting, the primer and paint are tightly bonded to the metal and are often applied to both sides of the metal. Post-painted parts generally do not include the primer and are not coated as evenly as prepainted coils.
During the design phase, and then regularly thereafter during regular production, coil coated parts are tested for corrosion-resistance with standardized testing using salt, chemical sprays, and/or water immersion. They are also examined for weathering resistance with accelerated ultraviolet and other environmental exposure tests. Test relating to stain resistance, welding capability, and resistance to abrasion are also performed depending on final application.
Continuous testing and adjustments made during the coating process ensure high-quality output. The paint thickness, curing temperature, and production line speed are monitored and controlled throughout the process. And then before leaving the production line, physical characteristics including gloss, color, hardness, adhesion, and resistance to cracking and marring are tested. This high level of control is not possible with post painting processes.
For products with exposed cut-edges, prepainted coatings outperform post painted coatings significantly. In field tests, prepainted metal louvers with exposed cut edges were compared to the same type of louvers with three different post paint applications (electrocoat, powder finish and spray finish). The louvers were exposed to the same elements in Florida for five years. The prepainted cut-edge far outlasted all three types of the postpainted edges. Visit www.coilcoatinginstitute.com/tutorials/# for details on the independent field study on cut edge.
All in all, manufacturers using prepainted metal will find superior coating durability, increased corrosion resistance and consistent color, texture and thickness in their finished products. For more information about converting to prepainted metal, visit: www.coilcoatinginstitute.org.
Jim Dockey is Director - CENTRIA Coating Services, and president of the National Coil Coating Association. For more information about processing coated coil, visit www.coilcoatinginstitute.org, or call the National Coil Coating Association at 216-241-7333.
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