A sometimes-underestimated part of the production cycle is the precleaning of products prior to PVD coating. Part of the PVD process itself is an etching step; however, this is mainly meant as a finishing touch to ensure a perfect adhesion. The technology most used in precleaning is ultrasonic alkaline cleaning.
A typical cleaning line consists of baths with water-based alkaline cleaning agents, rinsing baths with city water, RO water and DI water and a vacuum or hot-air drying station. Care must be taken so that no silicon containing buffing compounds are left in or on the products when entering the cleaning line. The cleaning line must have sufficient flexibility to ensure appropriate cleaning of all substrate materials. Agents used for brass may not be suitable for zinc. The DI water in the rinsing baths has to be good enough to ensure no drying stains will form on the products. Last, the drying station has to be adjustable to enable good drying of low- and high-temperature resistant materials.