B. R. Anton, Vapor Technologies, Longmont, CO; B. Mishra, Colorado School of Mines, Golden, CO
Decorative Ni/Cr electroplated layers on brass, zinc or ABS plastic are standard finishes on plumbing fixtures and door hardware. The chromium layer is traditionally deposited from a hexavalent chromium bath, but because of environmental and health concerns, an alternative such as trivalent chromium would be of interest as a replacement. Zirconium nitride (ZrN) deposited by a PVD method on these plated layers can offer an attractive brass-like finish and provide excellent wear, corrosion and chemical-resistant properties. It is of interest to study the performance differences of ZrN on chromium deposited from both hexavalent and trivalent baths. It was found that there was no significant difference in adhesion of the ZrN to either of the deposits but there was a great improvement in the corrosion resistance of trivalent chromium by the application of this PVD layer. Results of the performance evaluations will be summarized along with insight into the corrosion mechanisms.
Summary: Decorative electropated chromium coatings from trivalent baths are a cost effective and safe replacement for highly regulated and toxic hexavalent chromium. This study compares the mechanical and corrosion performance of PVD ZrN on these two materials for use on plumbing fixtures.