Volume 49, Issue 4 - April 2014


Suppliers Underscore Importance of Quality Anodizing in Fenestration

Anodized aluminum is used in a number of construction components, from curtainwall to windows, while subjected to a range of conditions, and requiring little or no maintenance. Improper anodizing can mean durability problems down the road, jeopardizing the intended life of a window or unit.

As with any component they source, fenestration manufacturers want to know they’re getting quality and durability with absolute consistency when it comes to anodized aluminum. From best practices in testing to attending to best practices in quality control, ensuring a consistently good product is something suppliers continue to tackle with meticulous care.

“Anodizing is the second hardest coating known to man, other than a diamond,” says Brent Slaton, national sales coordinator at Keymark Corp., who also serves as second vice president of the Aluminum Materials Council (AMC) with the American Architectural Manufacturers Association (AAMA).

Quality control for anodizing is generally good, experts say, but quality is such an important factor in durability that it’s “certainly something that those making these kinds of decisions need to be aware of,” says Don Sullivan, vice president at Ace Industries.

Certainly, proper anodizing involves care and precision. Quality control, Sullivan says, begins early—in the extrusion process, starting with the alloy. Next comes the anodizing itself.

“On our end, one of the more critical elements in the anodizing process in order to maintain quality is keeping the chemistry to the correct specifications,” Sullivan says. “This includes controlling daily titrations and proper temperatures. Of course all of these calculations and specifications are dependent on the job’s size and characteristics, but quality will and does take a serious hit if these numbers are off even a little. Additionally, drag out after rinsing must be kept to a minimum.”

A couple of ways buyers of anodized aluminum can examine for quality, according to Sullivan: if the anodizing job is done properly, the die lines from the extrusion process should no longer be visible, and the mil thickness and color should be consistent.

The Finishes Committee of the AMC, meanwhile, is taking a look at best practices for testing thickness. Anodized aluminum is rated for thickness by class—specifically, Class 1 or Class 2, explains Slaton. The stronger of the two is Class 1, which is used in the harshest of environments, such as a curtainwall on a high rise—a location that must require no maintenance. Sullivan also cites certain exterior locations with high UV factors or poor air quality.

Class 1 indicates a coating thickness of 0.7 mil, or 18 microns, and Class 2 indicates a thickness of 0.4 mil, or 10 microns. Another noteworthy differentiator: Class 1 must pass muster to withstand 3,000 hours of salt spray, while Class 2 must withstand 1,000 hours, according to Slaton, who is on the Finishes Committee.

The committee is discussing which of two coating tests to rely on; there are a couple of them being used. What the committee is looking into, says Slaton, is, “Are we measuring them all correctly and consistently?”

Both tests are accurate, according to Slaton, but ASTM B487 is much more involved to attain because it calls for testing by an outside facility. The ASTM B244 can be done in-house and online.

After discussions on the topic during AAMA’s annual meeting earlier this year, ballots have gone out in order to help the AMC committee make a determination on the issue. Ballot outcomes are to be discussed during the summer meeting in Indianapolis.

—Carl Levesque

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