The hazardous waste generated by wet coating processes has led to considerable interest in dry coating processes, such as physical vapor deposition (PVD). A critical step in the PVD process is the cleaning of the substrate prior to coating deposition. The ion beam sputtering of substrate surfaces has been shown to be an excellent means of removing surface contaminants and oxide layers, substantially enhancing coating adhesion. In standard practice, sputtering is accomplished with a low energy beam of argon ions, because gas ion sources are readily available, argon is easy to ionize, and argon sputtering coefficients are fairly high. However, coating sheet steel at processing rates on the order of 5 m2s-1requires beam currents of the order of several amperes. While the ion sources are readily available, the cost to vacuum pump the argon can become prohibitive. High current, pure beams of metal ions can be produced by vacuum arc technology. As vacuum arc sources do not require any carrier gas, the problem of gas pumping is eliminated. In addition, it should be possible to partially implant the surface during the sputter cleaning to further enhance the adhesion by addition of coating-compatible metal. The same equipment can also be used in place of gas ion sources for ion beam assisted deposition. As metal ions are incorporated into the coating, the species can be chosen to be compatible with the coating, e.g. chromium for chromium nitride deposition, or to provide additional properties, e.g. yttrium to stabilize zirconium oxide. A d.c. low voltage cathodic arc ion source has been developed, with ion beam currents in the ampere range even for very heavy metals, such as tantalum. The potential for this source for sputter cleaning and ion beam assisted deposition of sheet steel is discussed.
Treglio, J. R., & Perry, A. J. (1996). Surface processing of sheet metal using metal ion beams. Surface and Coatings Technology, 81(1), 87–91. https://doi.org/10.1016/0257-8972(95)02533-2