It’s Time to Think about Zinc Plating
Zinc electroplating protects metal architectural and structural elements against corrosion and adds to their aesthetic appeal.
Architects are specifying and your construction crews are probably installing more plated metal structural and decorative elements in commercial, office and hospitality projects these days. Here are some things you need to know about the benefits of plating these elements with zinc, which makes them both more functional and aesthetically appealing, and popular with architects.
The fundamental purpose of zinc plating is to protect the metal against corrosion that can affect the strength of structural elements. But zinc plating is also a valuable technique to enhance the visual appeal of decorative metal surfaces in both interior and exterior settings, particularly when a varied, imperfect industrial look is required.
Electroplated zinc plating provides a metal structural component with a clear, thin coating (approximately 5-25 microns) that protects the underlying surface without interfering with its functionality or its decorative features. This contrasts with thicker (100-150 microns) coatings applied by hot-dip galvanizing, which can fill in threads and holes and blur the appearance of decorative features. Also, the heat of the hot-dip process can warp long metal structural items and large steel panels.
In addition, zinc plating provides a “sacrificial coating.” This means that, if the plating is later scratched — even to the depth that the underlying bare metal is exposed — the surrounding zinc coating will “sacrifice” itself and continue to protect the exposed metal from corrosion. This level of protection can give interior decorative elements like wall panels a longer useful and attractive life.
In outdoor settings, standard zinc plating tends to weather and corrode, but still protect. If a weathered look is not the desired goal for a project, a zinc-nickel alloy plating will provide even greater protection — up to 10 times that of zinc alone — giving steel structures a longer corrosion-free working life comparable to the protection offered by hot-dip galvanizing, but without the thick coating and potential for warping.
Though most regularly used with carbon steel, zinc plating works equally well to protect other metals, including brass and copper.
But beyond its ability to protect metals, a less-recognized benefit of zinc plating is its ability to alter the surface appearance of a metal element to enhance its aesthetic appeal. The subtle unevenness of surface color that zinc plating produces on larger metal panels, for example, gives the surface a somewhat industrial look, enhancing an “industrial chic” design. Architects we have worked with have used this look to create eye-catching storefronts and interior wall surfaces in restaurants, retail spaces and offices.
In addition to the standard clear zinc plating, plating can also produce coatings in black, iridescent and olive drab. This is possible because zinc plating is a two-step process. A clear chromate finish is traditionally applied to further reduce the corrosion of the zinc plating. This can be replaced by a yellow hexavalent chromate that results in an iridescent surface finish, a black chromate that produces a black appearance or an olive drab chromate that results in a military look.
In one project, industrial-look panels were combined with unfinished wood slabs to create vintage-looking countertops and a bar in a restaurant. In another, large polished steel panels were coated with yellow hexavalent chromate to form a dramatic iridescent wall, as seen in the adjacent image.
Meet the King
For those less familiar with electroplating and the finishes and protections its processes can provide, it is essential to consult with a knowledgeable plater. Some effects may not be achievable with plating but may be possible with other processes. Powder coating, for example, will be more effective for outdoor installations, especially when zinc plating is used as the base coating.
Also, not all platers are equal in terms of their capabilities. Can the plater plate a large wall installation in one piece, for instance, or would it have to be done in sections, necessitating welds or other joints that might affect the finished appearance? Is the plater capable of applying the chromates needed to produce the desired finish color?
Our company’s operations boast the nation’s largest zinc tanks. Our “King Kong” plating line can service very large components reaching 27 feet long, 7½ feet deep, 46 inches wide and weighing 7,500 pounds. This makes it unnecessary to work with smaller components that would need to be assembled after plating.
Because of zinc-plated materials’ structural and aesthetic benefits, architects are likely to continue to specify these elements for building projects while working with platers to make sure the finished products last for years.
George Gatto Jr. is president of Chicago-located Gatto Industrial Platers Inc.