The NIST has developed a new reference material to aid quality control in the steel coatings industry. The new Standard Reference Material (SRM) 2426 is a 55 percent aluminum-zinc alloy certified by NIST not only for the aluminum and zinc content but also for silicon and iron, two important contaminants. First introduced commercially in the 1970s, 55 percent Al-Zn is widely used as a tough, corrosion-resistant coating for sheet steel, particular in roofing. The Zinc Aluminum Coaters Association (ZAC) claims the latter as the fastest-growing coated steel product in the world. The alloy is applied to sheet steel using a hot-dip coating process. Huge coils of cold-rolled steel wind through a vat of the molten alloy at speeds up to three meters a second. The coating must meet industrial standards for thickness and chemical composition, so the steel typically is sampled for quality control at regular intervals.
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