Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Table III. High-Efficiency Copper Cyanide Bath Potassium Copper cyanide Total potassium cyanide Total sodium cyanide Potassium carbonate Sodium carbonate Potassium hydroxide Sodium hydroxide Rochelle salt Free potassium cyanide by analysis Free sodium cyanide by analysis Temperature Current density Cathode efficiency Recommended agitation 60.0 g/L (8.0 oz/gal) 102.0 g/L (13.6 oz/gal) — 15.0 g/L (2.0 oz/gal) — 15.0 g/L (2.0 oz/gal) — 45.0 g/L (6.0 oz/gal) 15.0 g/L (2.0 oz/gal) — 60-71° Sodium 75.0 g/L (10.0 oz/gal) — 97.5 g/L (13.0 oz/gal) — 15.0 (2.0 oz/gal) — 15.0 g/L (2.0 oz/gal) 45.0 g/L (6.0 oz/gal) — C (140-160° up to 80 A/ft2 90-99% Mechanical, solution or air nificant copper thickness is required. The copper cyanide can be as high as 120.0 g/L (16.0 oz/gal) for applications such as wire plating. Although the brightness and grain refinement of the deposit can be improved by the use of peri- odic reverse current or current interruption, the best results are obtained by using suitable additives. Barrel Plating The strike bath, high-efficiency bath, or both in combination, can be used for bar- rel plating. Typical compositions for barrel plating are shown in Table IV. Bath Preparation Dissolve potassium or sodium cyanide in cold water. In a separate container, mix copper cyanide with water to form a thin slurry and slowly add to the potassium or sodium cyanide solution while mixing. The dissolving reaction is exothermic and the solution should not be allowed to overheat, as this may decompose some of the free cyanide. Add the rest of the required materials after dissolving the copper cyanide. Carbon treatment of the bath before use is recommended. All salts should Table IV. Copper Cyanide Baths for Barrel Plating Potassium Copper cyanide Total potassium cyanide Total sodium cyanide Potassium carbonate Sodium carbonate Potassium hydroxide Sodium hydroxide Rochelle salt Free potassium cyanide by analysis Free sodium cyanide by analysis Temperature 200 45.0-60.0 g/L (6.0-8.0 oz/gal) 80.3-109.5 g/L (10.7-14.0 oz/gal) — 15.0 g/L (2.0 oz/gal) — 7.5-22.5 g/L (1.0-3.0 oz/gal) — 45.0 g/L (6.0 oz/gal) 15.0-22.5 g/L (2.0-3.0 oz/gal) — 60-71° Sodium 45.0-60.0 g/L (6.0-8.0 oz/gal) — 64.5-88.5 g/L (8.6-11.8 oz/gal) — 15.0 g/L (2.0 oz/gal) — 7.5-22.5 g/L (1.0-3.0 oz/gal) 45.0 g/L (6.0 oz/gal) — C (140-160° 15.0-22.5 g/L (2.0-3.0 oz/gal) F) 15.0 g/L (2.0 oz/gal) F)

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