ZnCoat, developed by NOF Metal Coatings and Curtis Metal Finishing, is a finish designed to offer solutions for problems encountered by users of zinc plating for fasteners and small parts.
ZnCoat, a zinc-rich coating for ferrous metals, offers several major advantages for high strength fasteners when compared with electroplated zinc, its developers say. The finish is entirely chromium-free and is designed to provide superior corrosion resistance with a thin film, without risk of hydrogen embrittlement. ZnCoat is applicable for industries such as agriculture, construction, appliance, recreation, marine, etc., providing these markets with a higher performance alternative to conventional zinc plated finishes.
The zinc in the ZnCoat is passivated without the use of toxic materials, the companies say, adding that ZnCoat is free of chromium, nickel, cadmium, lead, barium and mercury and meets RoHS, REACH and WEEE environmental regulations.
By comparison, conventional zinc plating is passivated by the use of hexavalent or trivalent chromates. Chromates provide a thin-film passivation layer, but only on the surface of the zinc plating. Subsequently, during installation or in-use, this fragile film may be damaged and lead to premature zinc oxidation.
ZnCoat offers a solution to this problem: Environmentally friendly passivation agents and corrosion inhibitors are found throughout the film, and so the coating is far less susceptible to early failure. Furthermore, the unique corrosion inhibitors found in ZnCoat allow for continuous release throughout the life of the coating.
ZnCoat provides sacrificial protection as the zinc corrodes to protect the steel substrate. The coating is further enhanced by a self-repairing mechanism. If a coated fastener is abraded during installation, zinc oxides and carbonates form at a controlled rate at the damaged area, sealing the breach in the coating, and thus restoring barrier protection.
Developers say that compared with conventional zinc plating, ZnCoat consistently achieves more than 240 hours of ASTM-B117 salt spray corrosion protection, as well as higher cyclical corrosion performance and real-world outdoor weathering resistance.
ZnCoat is applied to steel parts through a non-electrolytic dip spin coating process, and is applied under license by Curtis Metal Finishing, which took the lead in bringing the product to market.