Innovation is often met with resistance, particularly by those who choose not to embrace it. Equivalent (EQ) coatings for cold-formed steel studs are no different. Introduced to the steel industry as an alternative to standard metallic coatings, EQ coatings have been falsely represented as not being equal to standard metallic coating.
The issue recently played out in the courtroom, where in a landmark case for the industry, an Ohio jury awarded a major steel stud manufacturer $49.5 million in damages after determining that the industry trade group, Certified Steel Stud Association, conspired to publish false and misleading statements about the company’s EQ-coated products. With all the misinformation in the marketplace, let’s help quell the confusion with four facts that every architect and specifier should know about EQ coatings.
EQ Coatings Comply with Building Codes
The prevalent code in use today, the 2012 International Building Code (IBC), recognizes EQ coatings as compliant through reference to ASTM C645 in Chapter 25. This standard explicitly requires that nonstructural steel framing members have a protective coating that conforms to ASTM A653, G40 minimum or have an equivalent corrosion resistance.
The 2015 version of IBC makes the acceptance of EQ coatings even clearer. Chapter 25 still references ASTM C645, yet the path to equivalent coatings for nonstructural cold-formed steel framing now goes through Chapter 22 (Steel), where the American Iron and Steel Institute (AISI) S220 is cited. AISI S220 permits the use of EQ coatings. Further, Table 2506.2 in the 2015 IBC specifies that for nonstructural cold-formed steel studs and track, the standards are AISI S220 and Section 10 of ASTM C645, aligning Chapters 22 and 25.
EQ Coatings are No Surface Treatment
EQ coatings are applied to zinc-coated steel sheets through a precise, digitally controlled reverse-roll coating process that permanently bonds the EQ coating to its zinc-coated substrate. During this process, the EQ coating penetrates and fills any cracks and voids in the existing zinc-coated substrate, thus sealing off the zinc layer and the carbon steel base metal to prevent formation of an oxide or rust layer.
The steel is then cured at an elevated temperature to complete the bonding process. Unlike surface treatments such as paints, primers and veneers, EQ coatings will never peel or blister because they are fully part of the substrate. EQ coatings maintain their integrity when scratched, cut, drilled or punched.
EQ Coatings Provide Superior Corrosion Protection Compared to G40
As mentioned, EQ coatings are required by ASTM C645 to provide a protective coating with an equivalent corrosion resistance to G40. Accelerated salt spray tests done in accordance to ASTM B117 prove they do by offering side-by-side comparisons that demonstrate how EQ-coated specimens perform against G40-coated specimens.
In the tests, specimens are placed in a sealed chamber into which a fog of heated salt-infused vapor is introduced. The temperature, humidity, salt solution mixture and water used are all specified and controlled. The testing runs continuously until there the G40-coated specimen fails. If the EQ-coated specimen outlasts it, then it is a clear demonstration of equivalent corrosion protection.
Repeatedly these tests have shown that G40-coated specimen samples-with an additional passivation coating no less-typically begin failing at 120 hours of exposure to salt spray and rapidly reach 10 percent surface rust failure (a threshold set by ASTM A1003) at update hours. In comparison, EQ-coated samples never reach above 3 percent surface rust, even after 240 hours of testing.
All Coatings are not Created Equal
The technology innate to high-performance EQ coatings is light years beyond the technology innate to surface treatments. There is really no comparison. EQ coatings provide superior protection and can be used in all types of interior nonstructural partitions, whether fire-rated or not. Further, EQ coatings allow manufacturers to use excess steel coils with a zinc-based coating that may otherwise not have been usable and turn it into a product that outperforms a G40-coated material, thus saving energy and removing material from the waste stream.
Specifying EQ Coatings
To include EQ-coated steel studs in project specifications, follow these suggestions:
- The applicable product standards are ASTM C645 for the 2012 IBC, or AISI S220 for the 2015 IBC. These standards define the stud steel sheet requirements, including minimum return lip, minimum prescriptive thickness or performance, and minimum section properties.
- Steel framing members must use an ASTM A653 G40 coating or a coating that provides corrosion resistance equivalent to a G40 coating. Any coating other than G40 must demonstrate it provides equivalent corrosion resistance. Code Compliance Research Reports
(CCRRs) are one way to demonstrate equivalence. - Manufacturers of steel framing members with EQ coatings should be able to supply a code report from an independent ANSI-accredited agency that certifies the coatings do in fact meet the ASTM C645 and AISI S220 equivalent corrosion protection requirement.
Following these guidelines will help ensure technical specifications direct contractors to use code-approved coatings and avoid the use of flimsy barrier coatings that, in all likelihood, get scratched, cut and damaged on the construction site. EQ coatings have proven to be an innovation to embrace–one that not only offers superior corrosion resistance, but is also approved by the IBC.
Michael C. Kerner, FASTM, CSI, CDT, is code development manager for cold-formed steel (CFS) framing manufacturer ClarkDietrich Building Systems, West Chester, Ohio. He can be reached at michael.kerner@clarkdietrich.com. For more information, visit www.clarkdietrich.com.