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Unraveling Coil Coating Myths

Mcn  Special  Feature  Sept16 3

The truth about coil coating and its features


Coil coating is a continuous and highly automated process for coating metal before fabrication. In one continuous process, a coil of metal, up to 72 inches wide moving up to 700 feet per minute, is unwound and both the top and bottom sides are cleaned, chemically treated, primed, oven cured, top coated, oven cured again, rewound and packaged for shipment.

Coil coating provides beautiful topcoats, durable surfaces, innovative applications, green benefits, and cost savings as compared to other substrates and other coating options. Coil coated products can be used not only for building exteriors, but also for a variety of interior finish applications including walls and ceilings.

Despite its many positive attributes, myths and misconceptions abound regarding coil coating. Here are a few of them.


Myth: It's Difficult to Form

Prepainted metal can be formed into many shapes and angles without sacrificing the integrity or appearance of the paint or metal substrate. "Most prepainted metal is formed after it is painted, and virtually all of the coatings used in the prepainting process are designed to withstand the rigors of forming without compromising their appearance or corrosion-prevention properties," says Michael Bonner, vice president of engineering and technology, Saint Clair Systems Inc., Washington, Mich.

Tony Nicol, global segment manager of coil and extrusion coatings at Columbus, Ohio-based AkzoNobel Coatings Inc., contends forming is actually one of the benefits of prepainted metal as the entire surface of the formed part is smoothly and uniformly painted. "When post-painting, oil and dirt can be difficult to remove prior to painting and uniform (even complete) coverage can be difficult to achieve especially with a consistent thickness," he says.

Thomas Rogers, associate product manager of Alcoa Architectural Products, Norcross, Ga., believes that prepainted metal, like Reynobond aluminum composite material, can be easily formed to achieve the same radius curves as post-painted metal finished with the same paint technology. "The material is extraordinarily flat, strong and highly formable," he says. "Reynobond panels can be rollformed, shaped, bent, folded, routed, punched or cut to achieve small-radius curves, reverse curves, angles and other shapes. Depending upon the paint technology and the metal used, the paint can actually be more formable than the metal substrate."


Myth: It Can't be Joined

Prepainted metal can be joined with adhesives, fasteners or welding. Lasting bonds can be formed with structural tapes and tie layers, which eliminate the need for fasteners. Fasteners, when used, can join roofing and sidewall panels, and are typically the same color of the panels.

They can also be seamed. "The seaming process protects the cut edge of panel from potential corrosion, as the seaming process protects the cut edge from exposure to the environment," says Jeff Alexander, vice president of sales-coil and extrusion business at Valspar Corp., Minneapolis.


Myth: The Edges Will Corrode

Although it seems unreasonable that a prepainted part with exposed cut edges would perform better than post-painting where all surfaces are covered, Bonner cites a study performed by the National Coil Coating Association (NCCA) that proved just that.

Prepainted metal actually does provide superior corrosion resistance, compared to postpainted parts. The pretreatments achievable in an advanced coil-coating process provide the best protective layer for the substrate metal: both sides of the material are cleaned, pretreated, primed and painted in the same operation. Alexander says advanced anticorrosive pretreatments and primers greatly limit cut edge corrosion.

Also, "By processing the metal in the flat, coaters can clean and coat both sides evenly to achieve the optimum surface conditions necessary to produce a durable and corrosion-resistant finish," Rogers says. "The advantage of this process is that it produces a very consistent film thickness in a tightly controlled environment. It is much more difficult to achieve a uniform finish on both sides of the metal when post-painting-the post-painting process is not as precise as prepainted technology and not always uniform. The post-painted parts will corrode worse along cut edges."


Myth: They Are All Identical

Is all coil coating basically the same? "Nothing can be further from the truth," Bonner says. "Each coated product must be optimized for the end use: from choosing the right substrate, to selecting the right coating, to applying it in the proper fashion. Many of the horror stories that are associated with pre-coated metal applications actually stem from poor execution in these key areas." Nicol advises that when purchasing coil coatings, "Do your research and make sure you are getting the quality you desire by selecting trustworthy suppliers and selecting the right coating type for your job."

Jerry T. Hatley Jr., executive vice president, CENTRIA Coating Services, Moon Township, Pa., says that, "Ironically, most paint lines were originally and individually engineered to address a few, primary end-use markets. And while many have been upgraded to address certain other end-use markets, virtually no coil coating line can claim to handle all end uses equally well."


Myth: It's Too Expensive

In many cases, prepainted metal is a lower-cost option than installing and supporting an in-line painting operation. "Advanced continuous coil coating technology is an efficient, cost-effective and eco-friendly process that produces superior quality finished goods, unlike post-painted materials," says Rogers. "With this advanced technology it is possible to coat thousands of square feet of metal per minute; we can also produce unlimited quantities of material with uniform color. Post-painting not only requires additional labor and materials costs, but also does not always produce consistent results."

Prepainted metal offers a number of benefits to post-painting which can have a positive benefit to the total cost of the product. Nicol stresses that all factors need to be considered when evaluating the expense involved such as total paint usage due to uniform thickness on prepaint (which also typically uses a thinner layer of paint), paint waste from the post-paint process both in wasted material and scrap costs, maintaining of paint booths for post-paint, environmental considerations and associated costs.

Alexander stresses that while the cost of a prepainted metal roof can be more expensive than traditional roofing materials, metal roofs can last up to 50 years. "Virtually no maintenance is required and myths, such as 'my roof is noisy when it rains' and 'any sort of hail storm will destroy my roof' simply are not true," he adds. "Additionally, a prepainted metal roof, if coated with a solar reflective coating, will achieve energy savings as roof surface temperatures can be greatly reduced, versus traditional roofing materials."


Myth: It's for Agricultural Applications Only

While there are certainly a number of applications within agricultural and industrial buildings, prepainted metal is available in a variety of aesthetics, profiles and textures that can enhance high-end buildings as well. "AkzoNobel supplies coatings that are used in wood and stone prints and a variety of roofing tile looks such as shake, clay tile and slate, as well as wrinkles and textures, all on steel and aluminum substrates," Nicol says. "These products can be seen on high-end residential and commercial buildings, increasing value and durability for these facilities."


Myth: It's Hard to Handle

With uniform cleaning, pretreatment and durable coatings, prepainted surfaces are resistant to marring when using reasonable storage and normal handling practices. Today's paint finishes are typically very hard and do not scratch easily. "Certain paint technologies are harder than others, but typical job-site handling will not cause damage to the metal substrate or the paint finish itself," Alexander says. Protective films can be applied to prepainted metal panels during the painting process that provide excellent protection during transportation and fabrication. "In modern manufacturing operations, most coils are handled by lifting from the center, either with a forklift, or by an overhead crane, so surface marring never occurs or is limited to the inner-most wrap in the coil," Bonner says. Contractors should handle a prepainted product on a job site with the same care and attention as they would handle a post-painted product.


Sidebar: The Source of Coil Coating Myths

In many respects, coil coating myths are related to an overall changing of the guard in this industry segment. Years ago, the individuals that we speak of today as industry legends were in fact very active in our business. There were certain truths about coil coating that were, more or less, universally understood. And while the new talent brings extraordinary intelligence, energy and vitality to the industry, we also see a tendency toward reinventing the wheel from time to time. Unlike many career disciplines, there's obviously no accredited degree program for coil coating at the college level. National Coil Coating Association has consistently offered educational tools for people new to the industry, but we have to get serious about further educating the next generation of coil coating personnel. Let's not lose the tribal knowledge that made us so successful, but make a concerted effort to pass this along.

Secondly, we ourselves sometimes fall into the trap of considering coil coatings as commodities, and unfortunately keep those myths alive. The fact is that coil coated substrates are highly engineered products. When viewed with respect to the overall supply chain, we are the last stage of high-speed, bulk raw material refinement before end-use fabrication. Therefore, much is expected from us.

Jerry T. Hatley Jr., executive vice president, CENTRIA Coating Services, Moon Township, Pa.