Plate Better, Longer--ELECTROLYTE MAINTENANCE TECHNIQUES CAN EXTEND BATH LIFE

摘要

Adsorber polymer technology is user-friendly and safe, and is already in use in several plating facilities. Because it requires periodic regeneration of the adsorber polymer, it can remove contaminants from plating baths in what is best described as a "semi-bypass" process. A well-chosen adsorber system can significantly reduce bath contamination and thus improve bath performance and stability. Two points that must be addressed are the initial capital investment and the relatively high cost of replenishment. Liquid-liquid extraction shows significantly higher selectivity than the adsorber polymer technique, efficiently removing contaminants while leaving needed additives such as saccharine brightener in the bath. The process can be operated in bypass mode to considerably increase bath operational life. However, other problems, including the relatively long time needed for phase separation in units based on the mixer settler principle, may occur. The most efficient extraction medium tested was butyl acetate, which has exhaust and odor concerns. Diaphragm-supported liquid-liquid extraction using micropo-rous pipes to allow the exchange of impurities without mixing addresses the phase separation issue by maintaining the phases separately. However, pressure must be kept stable on both sides of the membranes to avoid possible breakthroughs.