Metal Finishing Guide Book

2013

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Table I. General Purpose Copper Cyanide Strike Potassium Sodium Copper cyanide 30.0 g/L (4.0 oz/gal) Total potassium cyanide 30.0 g/L (4.0 oz/gal) 58.5 g/L (7.8 oz/gal) — Total sodium cyanide — 48.0 g/L (6.4 oz/gal) Potassium hydroxide 3.75-7.5 g/L (0.5-1.0 oz/gal) — — 3.75-7.5 g/L (0.5-1.0 oz/gal) Sodium hydroxide Potassium carbonate 15.0 g/L (2.0 oz/gal) — — 15.0 g/L (2.0 oz/gal) 30.0 g/L (4.0 oz/gal) 30.0 g/L (4.0 oz/gal) Sodium carbonate Rochelle salt Free potassium cyanide by analysis 11.25-15.0 g/L (1.5-2.0 oz/gal) — — 11.25-15.0 g/L (1.5-2.0 oz/gal) Free sodium cyanide by analysis Temperature Current density 24-66°C (75-140°F) 0.5-4 A/dm2 (5-40A/ft2) Time Cathode efficiency Recommended agitation 30 sec to 2 min or until fully covered 30-60% None or mechanical Strike-Plate Bath The strike-plate bath (see Table II) is the one most used for the plating of zincated aluminum. It is also used for zinc die castings and other metals that are subject to attack by subsequent plating baths or finishing operations that require more than a strike deposit for protection. This formulation eliminates the need for two baths—a strike followed by a plate in a high efficiency bath. Deposits range from 3.0 to 5.0 μm (0.12-0.20 mil) in thickness for the parameters given in the formulation. High-Efficiency Bath The high-efficiency bath (see Table III) is used when a rapid buildup of a sigTable II. Copper Cyanide Strike-Plate Bath Potassium Sodium Copper cyanide 42.0 g/L (5.6 oz/gal) 42.0 g/L (5.6 oz/gal) Total potassium cyanide 66.6 g/L (8.9 oz/gal) — Total sodium cyanide — 51.9 g/L (6.9 oz/gal) Potassium carbonate 30.0 g/L (4.0 oz/gal) — — 30.0 g/L (4.0 oz/gal) Rochelle salt 60.0 g/L (8.0 oz/gal) 60.0 g/L (8.0 oz/gal) Free potassium cyanide by analysis 5.7 g/L (0.8 oz/gal) — — 5.7 g/L (0.8 oz/gal) Sodium carbonate Free sodium cyanide by analysis pH Temperature Current density and time 10.2-10.5 40-55°C (100-130°F) Initial (strike) 2.5-3.0 A/dm2(25.0-30.0 A/ft2) for 2 min. Final (plate)1.0-1.5 A/dm2 (10.0-15.0A/ft2) for 3-5 minutes. Cathode efficiency Recommended agitation 30-50% None or mechanical 271

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