Powder Coating Architectural Products

Q. We are a job shop but want to powder coat for architecture. What do we need to do to coat for that market?

A. The American Architectural Manufacturers Association (AAMA) has developed performance specifications for aluminum in architectural applications, but there are no specifications for steel, galvanized steel or other metal substrates. This means you can use architectural powder on these substrates, but it won’t meet AAMA specifications, except for gloss and color retention. However, if the substrate is properly pretreated and the AAMA-compliant powder coating is properly applied, cured and maintained, it will continue to perform as designed, independent of the substrate

You must have an AAMA-recognized pretreatment system. Iron-phosphate and zinc-phosphate systems are not recognized, but newer zirconium-type, chrome-phosphate and non-chrome dry-in-place technologies are recognized and have been thoroughly tested. Get with your pretreatment supplier and explain that you are looking to pretreat aluminum in compliance with AAMA specifications.

Architectural powder coatings are engineered to meet three different levels of the AAMA specifications, and it is important to know which level you want to meet. Next, as always, it is imperative to review the Technical Data Sheet (TDS) for the powder coating, where film thickness and cure requirements are listed. Some coatings require extended time at temperature compared to conventional coatings that you might have experience with.

Many powder coating suppliers have approved architectural powder applicators. Contact the suppliers to determine their requirements, as well as what testing is required.

Here are some other questions and answers related to architectural coating:

What are the differences among AAMA 2603, 2604 and 2605? These are primarily differentiated by the required length of weathering testing. AAMA 2603 is primarily used for residential applications and requires one year of South Florida weathering testing; 2604 is used for high-end residential and commercial/industrial applications and requires five years weathering testing; and 2605 is used for monument projects and requires 10 years of weathering testing.

Since AAMA 2605 has the highest specification for weathering, isn’t it the best powder for any application, then? No. AAMA 2605 powder coatings are specifically engineered for architectural applications, and they also cost as many as 10 times that of the typical polyester (TGIC or TGIC-free) powders you may be familiar with. Always discuss the end-use application with your powder supplier and pick the best “fit for purpose” based on cost. As UV resistance increases, some mechanical properties usually decrease. Lower UV-resistance products are therefore better suited for applications in high-traffic areas such as fences and railings.

How can I save money on these architectural powder coatings? As with all powder coatings, only apply to the required film thickness listed on the TDS. It is worth the investment to purchase and use a film thickness gage. Applying 3.5 mils when only 2.5 mils are required means you are using 40 percent too much paint. That might not sound like much, but if you routinely do that and your total annual spend for powder coatings is $300,000, you will be able to save $120,000 a year just by measuring and controlling film thickness. And the customer isn’t paying for the extra mil of coating; you most likely quoted the job at 2.5 mils, so you have likely lost your profit by over-applying. If cash flow is becoming an issue for your business, fixing this might be the solution.

Compare applied cost instead of cost per pound powder. In some cases, properly engineered coatings may have a higher cost per pound, but provide significant savings in applied cost. For example, coatings that have less extender have lower specific gravity and greater charge-ability, providing greater first-pass transfer efficiency and reducing the need to recycle while maintaining more consistent film thickness.

What does it mean if a powder is listed as “super-durable?” Super-durable refers to its extended weathering performance. However, just because a coating is listed as super-durable doesn’t mean that it meets AAMA 2604. Typically, the TDS will specify if a coating meets AAMA 2604.

Why is it so hard to build film or get into Faraday Cage areas with some powder coatings, but other coatings seem to “jump” on the part? You must always have a good ground in electrostatic powder application. If this difficulty is still the case after checking ground, then a likely reason is the engineering of the powder coating.

Powders primarily are made up of resin, pigment and additives. Most have some amount of extender, and these extenders typically do not charge as well as the resin does. A powder with a greater amount of extender, will generally cost less per pound but also generally will have increased specific gravity. Typically, sprayers have more difficulty applying products with higher specific gravity. By comparison, powders with less extender generally will have better charging characteristics, as described earlier.

Another issue could be the powder’s particle distribution characteristics. Powder coatings follow a bell curve distribution: Too many fine particles or too small of a mean particle size can impact the application..

What are metallic-effect powder coatings, and do they require a clear coat if they will be used outdoors? Metal-effect powder coatings have a base powder and either a metal flake (leafing or non-leafing) or a mica component. These coatings can be produced by bonding the metallic pigment to the base powder particle, a process that allows the powder to be reclaimed and reused. In some cases, the powder coating can be used on outdoor products without a clear coat; you should refer to the individual TDS to determine if the clear coat is required.

Mike Withers is the architectural segment leader for powder coatings at Axalta Coating Systems. Visit axaltacoatingsystems.com.