Coil coating is the continuous industrial process for efficiently coating coils of metal. Because the metal is treated before it is cut and formed, the entire surface is cleaned and prepared, providing tightly-bonded finishes. The process is generally automated since there are numerous repetitive steps. Coil-coated metal is more durable and more corrosion-resistant than post-painted metal. In addition, the process is close to 100% efficient so from an environmental standpoint, it is an extremely good coating method.
Coil-coated metal substrates include:
- Steel
- Galvanized steel (zinc coated steel — hot dip and electrogalvanized)
- Galfan (~95% zinc and 5% aluminum coated steel)
- Cold rolled and hot rolled steel
- Galvalume (43.5% zinc, 55% aluminum-with 1.5% silicon coated steel)
- Aluminum
- Aluminum grade 3003
According to EN 10169 : 2010 is a process in which an (organic) coating material is applied on a rolled metal strip in a constant process that includes cleaning, and chemical pre-treatment of the metal surface and either one-side or two-side, single or multiple application of (liquid) paints or coating powders which are subsequently cured or/and laminating with permanent plastic films.
In the study period of 2016-2026 with the base year of 2020, Asia-Pacific is both the fastest growing and largest market, with approximately 6.9% CAGR in Asia-Pacific, which rolls up to 4.7% globally. This leads to $6.8 billion by 2030 and over $5 billion in 2020. This included Plastisol, Polyurethane (PU), Polyester, Polyvinylidene Fluorides (PVDF) and Silicone Modified Polyester. Each category of coatings has a different growth rate which is to be expected. As an example, the fluorocarbon coating market has an approximate CAGR of 9%.[i]
Pre-painted metal is used in a variety of products. It can be formed for many different applications, including those with T bends, without loss of coating quality. Major industries use pre-painted metal in products such as building panels, metal roofs, wall panels, garage doors, office furniture (desks, cubicle divider panels, file cabinets, and modular cabinets), home appliances (refrigerators, dishwashers, freezers, range hoods, microwave ovens, and washers and dryers), heating and air-conditioning outer panels and ductwork, commercial appliances, vending machines, foodservice equipment and cooking tins, beverage cans, and automotive panels and parts (fuel tanks, body panels, bumpers). The list continues to grow, with new industries making the switch from post-painted to pre-painted processes each year.
The major global manufacturers for this segment are BASF SE (Germany), Akzonobel N.V. (Netherlands), PPG Industries Inc. (U.S.), Sherwin-Williams/Valspar (U.S.), DuPont (U.S.), Henkel AG & Company (Germany), Kansai Paint Chemical Limited (Japan), The Beckers Group (Germany), The Wacker Chemie AG (Germany), and others.
The metal substrate (steel or aluminum) is delivered in coil form from the rolling mills, often from Asia. The coil is positioned at the beginning of the line, then unwound at a constant speed, passing through the various pre-treatment and coating processes before being recoiled (see figure provided or previous figure).[ii] Coil weights vary from 5-6 tons for aluminum and up to about 25 tons for steel. Two strip accumulators at the beginning and the end of the line enable the work to be continuous, allowing new coils to be added (and finished coils removed) by a metal stitching process without having to slow down or stop the line.
Various high-tech, complex coatings are applied with the coil coating process. Some of those functional coatings include coatings for cool metal roofing (CMR) materials, smog-eating building panels, antimicrobial products, anti-corrosive metal parts, and solar panels. Pretreatments and coatings can be applied with the coil coating process in very specific, thin, uniform layers, and can make some complex coatings viable and more cost-effective.
The largest market for pre-painted metal is in both commercial and residential construction. It is chosen for its quality, low cost, design flexibility, and environmentally beneficial properties. Using pre-painted metal can contribute to credit toward LEED certification for sustainable design. A wide arrange of color options are available with pre-painted metal, including vibrant colors for modern designs, and natural weathered finishes in rustic expressions. Pre-painted metal also can be formed, almost like plastic, in fluid shapes. This flexibility allows architects to achieve unique, expressive designs using metal.
Resources
- [i] National Coil Coating Association – NCCA – Prepainted Metal – Coil Coated Steel and Aluminum
- [ii] Learn about the Remarkable Technology of Coil Coating (ulprospector.com) | Ron Lewarchik 6/11/21
- Coil Coating: Prepainted Steel and Aluminum – Kloeckner Metals
- Protective Coil Coatings | What to Know, What to Ask? (american-coil.com)
- Elvacite® – Durable Coil Coatings, Product Article – ChemPoint
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