Choosing Durability

by Marcy Marro | October 1, 2020 12:00 am

For high-performance polyvinylidene fluoride (PVDF) finishes, AAMA 2605-20 “Voluntary Specification, Performance Requirements and Test Procedures for Superior Performing Organic Coatings on Aluminum Extrusions and Panels,” a standard of the Fenestration and Glazing Industry Alliance[1] (FGIA) is the industry-leading guideline. Updated in 2020, finishes that meet AAMA 2605-20 are inherently inert and have the ability to withstand long-term ultraviolet radiation, which results in the highest level of color/gloss retention and chalk resistance. PVDF finishes also resist acids, alkalis, oils and dirt pick-up.

Architectural anodizing, a process utilized for more than 90 years, continues to offer numerous benefits to aluminum product manufacturers and the building industry. Anodize finishes are created through an electro-chemical process where the aluminum on the surface of a part is converted from aluminum to aluminum oxide, an extremely hard and durable surface finish. In fact, aluminum oxide is second only to a diamond in its hardness. Due to these properties, and because the coating is integral to the part itself, anodize is highly resistant to marring, scratching and other damage often associated with the needs of high-traffic environments.

When selecting and specifying anodize finishes, it is important to understand what is truly being offered. For architectural aluminum products’ finishes, there are two primary specifications:

• AAMA 611-14, “Voluntary Specification for Anodized Architectural Aluminum,” which details Class I, a high-performance, durable finish used for exterior building products, and Class II, a lower performance, less-durable finish recommended for interior applications,
• AAMA 612-20, “Voluntary Specification, Performance Requirements, and Test Procedures for Combined Coatings of Anodic Oxide and Transparent Organic Coatings on Architectural Aluminum.”

Both are standards of the FGIA and each addresses aluminum finishes, but there are several key differences.

The obvious difference between the two specifications is that in AAMA 611-14 the only coating called for is an anodic coating, while AAMA 612-20 calls for a very thin anodic finish with an organic coating (paint) applied over the top of the anodic coating.

• The AAMA 612-20 specification requires the anodize thickness to be 10 microns (0.39 mils), which is approximately half the anodize thickness required by AAMA 611-14 Class I specification.
• The organic coating overlay described in AAMA 612-20 also has a minimum thickness of 8 microns (0.31 mils). For comparison, AAMA 2605-20 requires a coating thickness of 30.48 microns (1.20 mils) to protect the aluminum.

Finishes offered with the 612-20 specification are referred to as “white anodize.” The white color is achieved by applying a thin, organic coating over the aluminum’s minimal, integral anodic finish. Unfortunately, when paint covers the aluminum oxide, the extreme hardness and wear properties of the anodize are compromised. As a result, the coatings specified in AAMA 612-20 do not have nearly the surface hardness, performance benefits and durability of traditional anodize coatings. Similarly, they also do not have the weatherability, color fastness and the longer warranties associated with high-performance PVDF coatings that meet AAMA 2605-20.

If durability is the priority in selecting a finish for architectural aluminum, coatings that only meet the AAMA 612-20 specification will not suffice. For the most durable and wear-resistant finish available, choose anodize specified to meet AAMA 611-14 Class I. For the most weather-resistant, chemical-resistant organic coating in an expansive palette of colors choose a high-performance PVDF coating that meets AAMA 2605-20.

In coastal climates and corrosive environments, finished architectural aluminum may be required to exceed AAMA 2605-20. For these applications, specify a 70% PVDF coating system with chrome phosphate pretreatment along with an inhibitive chrome-rich primer. Anodize finishes that meet AAMA 611-14 Class I also can be a suitable choice for coastal climates.

The AAMA 2605-20, AMMA 611-14 Class I and AAMA 612-20 specifications describe test procedures and performance requirements for the highest performing organic coating systems and anodize finishes available for architectural aluminum products. To qualify as meeting one of these specifications products tested shall meet the requirements:

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Tammy Schroeder, LEED Green Associate, is a marketing manager at Wausau, Wis.-based Linetec[2]. With 20 years of experience in the finishing industry, she serves as an industry educator on high-quality, high-performance architectural coatings and services. Schroeder can be reached at tammy.schroeder@linetec.com[3].

Source URL: https://www.metalarchitecture.com/articles/choosing-durability/

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