Volume 48, Issue 4 - April 2013


Metal Coating Options Seek New
Ways to Add “Greenness” to Glazing

It seems every day brings a new announcement about how glass goes green, but when it comes to the paints and coatings used on the surrounding architectural metals, are products becoming equally as environmentally friendly?

According to John B. McClatchey Jr., sales manager for Southern Aluminum Finishing Co. Inc. in Atlanta, the answer is a definite “yes.”

However, the answer comes in several parts, as efforts have been made to improve powder-coating, anodizing processes and wet paint, providing plenty of options in the metal color department.

First, as McClatchey explains, “Historically the term ‘powder coat’ has a negative connotation in the glass industry. There was a rash of powder coating projects in the ’80s when the powder coats didn't appear the same as the liquid Kynar paints. As a result, companies and individuals began to think of powder coats as having a different gloss level or an ‘orange peel’ effect relative to liquid Kynars. That is simply no longer the case. It has been a challenge to promote this environmentally cleaner process because of the misunderstanding many people have when they hear the term powder coats. You cannot tell the difference between the powder coats we apply and a liquid Kynar paint.”

McClatchey continues, “Some of the architectural paint manufacturers are now selling powder coatings that meet the same specification (AAMA 2605, Voluntary Specification, Performance Requirements and Test Procedures for Superior Performing Organic Coatings on Aluminum Extrusions and Panels) as the liquid Kynar paints. The coatings are indistinguishable from the liquid paints and exhibit the exact same appearance and durability. Powder coated AAMA 2605-compliant coatings release none of the harmful volatile organic compounds (VOCs) into the atmosphere that are a by-product of liquid Kynar paints. The traditional liquid paints consist of pigment, resin and solvent. The new AAMA 2605 powder coatings have the pigment encapsulated in a powdered resin. There is no harmful solvent released.”

As this powder coat update gets out, “The aluminum extrusion window market is converting more paint lines to powder coatings,” says Scott Moffatt, director of marketing for coils and extrusions at PPG Industries in Pittsburgh. “Powder coatings are zero-volatile organic compound (VOC), and the product is recycled.”

Brent Slaton, national sales coordinator for Keymark Corp. in Fonda, N.Y., concurs that powder coating presents less than 1-percent VOC, and anodizing is virtually VOC-free, making these processes far “more environmentally friendly than wet coatings.” And today, Slaton finds, the trend has been more anodizing. “I would say in recent years we have seen an increase in jobs/projects requiring anodic coatings” he says. “We have been almost at capacity as far as anodizing goes.”

“Recent developments in anodizing have resulted in a more environmentally friendly process,” McClatchey agrees. “A process referred to as ‘acid etch’ makes for a more uniform appearance on extruded aluminum. The process reduces or eliminates the die lines, which are streaks in the metal that are traditionally the result of the anodizing process. Because this process requires less etching time in the tank, it significantly reduces the amount of metal lost in the anodizing process. As there is less aluminum etched off of the metal, there is less sludge in the tanks and thus less waste disposal. A quick dip in the traditional caustic etch tank is still required so, if the customer wants, that process is still available.”

However, paint should not be ruled out as an option, as more coaters are adapting equipment to remove VOCs from the wet paint process. “If the [paint] applicator has the proper equipment, and is doing the right, eco-friendly thing, then they should be utilizing the Roxidizer,” Slaton says.

Keymark runs these VOC abatement systems on all paint lines in its two extrusion facilities. “A Roxidizer (or afterburner) burns off the majority of the VOCs. It burns off the VOCs that are in the solvents during the application process. Your Roxidizer, or your afterburner per se, burns off about 96 to 97 percent of all the VOCs that would normally be emitted into the atmosphere. And there are many extruders/applicators that do not have Roxidizers,” Slaton adds.

As a result of improvements in this paint technology, an audience continues to grow for the use of paints. “We are starting to see an increase in paint, more toward the more neutral colors,” Slaton says. But overall that number is still small, as few clients are set on finding a paint that meets both their aesthetic needs and their green building requirements.

“LEED documentation is becoming more prevalent in the architectural industry due to energy and environmental concerns. Of those questions asked for LEED documentation is ‘how many pounds of VOCs per gallon are in the coatings applied to the extrusions specified on the job?’” he says. However, he adds that at this stage it’s typically a requirement only on the highest-tier of certification. “Typically they want more information on the recycled content of the aluminum and they’re also looking toward the proximity to the jobsite,” Slaton says.

Finally, metal pretreatment efforts also are seeing some improvement in the type of materials used. “There is an effort in [the aluminum extrusion window] market to eliminate chrome from pretreatment systems and primers,” Moffatt explains. “This will take time, since chrome is essential for corrosion protection but some accounts are converting away from chrome for less severe locations.”

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