Coat, don’t plate: General Industry Coverage

Hard-chrome plating (HCP) provides parts, such as ones for the aerospace industry, with a wear- and corrosion-resistant surface but requires the use of hexavalent chromium salts. Those salts are genotoxic carcinogens and pose health and environmental hazards, and, therefore, are restricted in the U.S. by the Occupational Safety and Health Administration and in the European Union by REACH (Registration, Evaluation, Authorization and Restriction of Chemicals).

Courtesy of Hardide Coatings

Parts to be coated with Hardide-A are loaded into a CVD coating reactor.

“Hexavalent chromium has been a concern for many years, but the alternatives have always been limited,” said Dan Wilson, business development manager for Hardide Coatings Inc., which offers the Hardide-A coating as an environmentally and worker-friendly alternative to HCP.

Workers applying hexavalent chromium-containing products are exposed the most, particularly when chrome plating because the processing bath produces bubbles, which generate a difficult-to-capture fog, according to Dr. Yuri Zhuk, technical director for U.K.-based Hardide Coatings Ltd.

Hardide-A, on the other hand, is a tungsten carbide-based CVD coating that is applied in a coating reactor, which doesn’t expose workers to environmental hazards. Zhuk added that although spray coatings, such as high-velocity oxy-fuel, are considered the best available alternative to HCP, those are line-of-sight processes that can only be applied to external surfaces because a spray gun can’t fit, for example, into a small bore.

“In the past, hard chrome was often seen as the best option for hardening interior surfaces because spray coatings are difficult or impossible to apply in tight spaces,” Wilson said.