NOF Metal Coatings North America Inc. and Curtis Metal Finishing Company have launched ZnCoat, a new finish that offers effective solutions for the problems that have been 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 to electroplated zinc. The finish is chromium-free (no hexavalent or trivalent chromium), and provides corrosion resistance with a thin film, without risk of hydrogen embrittlement. ZnCoat is applicable for construction, appliance, and marine applications, offering an alternative to conventional zinc-plated finishes.

The zinc in the ZnCoat is passivated without the use of toxic materials. ZnCoat is free of chromium, nickel, cadmium, lead, barium and mercury and meets RoHS, REACH & 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, the fragile film can be damaged and lead to premature zinc oxidation. ZnCoat uses environmentally friendly passivation agents and corrosion inhibitors throughout the film, and so the coating is less susceptible to early failure, according to the company.

Compared to conventional zinc plating, ZnCoat consistently achieves over 240 hours of ASTM-B117 salt spray corrosion protection, as well as higher cyclical corrosion performance and real-world outdoor weathering resistance, said the company.

For threaded fastener applications, ZnCoat has a tight, consistent friction coefficient (CoF). Lower CoF can be achieved with conventional wax-type topcoats, as is common with electroplated fasteners. ZnCoat is compatible with microencapsulated, anaerobic and nylon type thread adhesive and sealant patches.