FGIA Analysis July/August 2023August 17th, 2023 by Nathan Hobbs
Clearing the Air: An Updated Spec Aims to Help In the Search to Prevent Corrosion
By Glenn Ferris
When it comes to resiliency associated with fenestration and its related components, Florida’s stringent hurricane-resistance standards come immediately to mind. That said, hurricane-level events are by no means the only weather-related troubles architects and builders must consider in satisfying safety and performance requirements. Beyond rain and water, another critical factor (at least in Florida and the Southeast coastal regions) is the high degree of salt content not only whipped around by powerful storms but found in everyday conditions. This leads to “trouble” that isn’t storm related at all, and it’s rather insidious in nature—potentially leading to rust and corrosion.
In dealing with such deterioration, the historic workhorse for protective metal coatings was cadmium. But like the use of asbestos in fire protection, cadmium is no longer an acceptable coating solution. In the transition to find and implement acceptable alternatives—such as zinc, nickel and chromium—the absence of a simple but critical data element contained in a much older specification created significant confusion in the industry. This change led to the issuance of an updated protective coatings specification by FGIA in the form of AAMA 907-23, Voluntary Specification for Corrosion Resistant Coatings on Carbon Steel Compoents Used in Windows, Doors and Skylights.
In with the New
Last updated in 2015, the major change from the earlier version of the specification mostly involves new language and the return of an old industry friend—a table which had been included in the 2012 edition that related to compliance with required ASTM or ISO specifications. In drafting AAMA 907-15, the note and table from the 2012 specification had a very limited listing of coating materials, but manufacturers missed it. This absence created a lot of confusion, which is something FGIA heard about when soliciting feedback for the 2023 revised anti-corrosion specification.
The revised table, now included in section 5.2.1, addresses zinc plating, zinc plating of threaded fasteners, and nickel and chrome plating—the cadmium replacement the industry has since transitioned to in order to meet new materiality, environmental and safety requirements. Regarding the science behind the now more commonly employed coatings, it’s about better hexavalent bonding. This is a chemical process involving the degree of reactivity where the oxidation number of metal compounds changes, resulting in a more controlled corrosion.
To isolate the steel used in fenestration components from moisture and oxygen coatings are applied.
One protective coating that you may be familiar with is a zinc coating, which is commonly referred to as a galvanic coating. These coatings do not prevent oxidation from occurring but in some instances they themselves oxidize to form a layer that slows or prevents the underlying steel from being reached by moisture or oxygen.
Another major aspect of the new specification delves into the definition of “substantial substances,” or areas that are openly visible and exposed once a fenestration component is installed.
AAMA 907-23 is now available for purchase in the FGIA online store.
Glen Ferris is fenestration standards specialist for the Fenestration and Glazing Industry Alliance (FGIA).
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