Metal Finishing Guide Book


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Figure 3. Mixed-bed DI system showing anion and cation exchange on the resin beads. • Compressed Air (from main system) • Electrode rectifier The electro-precipitation allowed salt and organic build-up so the rinse water system was drained and replenished on a regular basis to keep the contaminant levels down. Due to this drain-and-replenish cycle, the rinse water quality gradually degraded after the replenishment process. Therefore, the rinse water had to be monitored to prevent poor rinsing of parts and chemical contamination of the plating tanks by dragout from the rinses. New Rinse Water Treatment Process. The new process starts with a reverse osmosis system to pretreat the incoming city water. This water serves as makeup water for tank evaporation and tank changeovers. An RO system (reverse osmosis) has a membrane that is permeable to water and a small percentage of ions, typically less than 5% of the total ion loading. 675

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