Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Figure 4: Even with very limited space, the ENfinity® SteadyState equipment can be integrated into existing lines. This pictures shows a unit operation with two independent tanks. ically consistent 3 MTO solution age level. Due to the high costs of dumping 1/3 of the process solution with every MTO, the only application continuing to use this principle is the production of memory discs for high-phosphorus EN. So far, electrodialysis—globally only offered by two chemistry suppliers—has been state-of-the-art when it comes to the advanced continuous operation of electro- less nickel with significant consumption. By applying a current between selective membranes, breakdown and by-products are removed from the bath solution, pro- viding, in principle, an unlimited/endless bath operation. Besides being rather ser- vice-intensive and sensitive to membrane leakage, the main limiting factor for elec- trodialysis is the high investment cost. The new technology presented in this paper offers a third, superior way to simply operate electroless nickel continuously, in all phosphorus ranges, at low cost. ENfinity® SteadyState combines the advanced bath life of sulfate-free EN with dilution of the process solution at high MTO level. The process is typically "frozen in" at 10 MTO. The ENfinity® process provides full performance at mod- erate temperatures at this operation point. The specific gravity and, as a result, the entire plating chemistry is kept constant by removing only about 7% volume per MTO, in addition to an estimated natural drag out of about 3.3%. The dilu- tion and replacement by new make up is done entirely automatically and in 373

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