Metal Finishing Guide Book

2013

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Table IV. Bath Parameters for an Alkaline Zinc-Cobalt Bath Parameters Amounts Zinc metal 6-9 g/L Sodium hydroxide 100-130 g/L Cobalt metal 30-50 mg/L Temperature 21-32°C Cathode current density 2.0-4.0 A/dm2 Anodes Steel Table V. Bath Parameters for an Acid Zinc-Iron Bath Parameters Amounts Ferric sulfate 200-300 g/L Zinc sulfate 200-300 g/L Sodium sulfate 30 g/L Sodium acetate 20 g/L Table VI. Bath Parameters for an Alkaline Zinc-Iron Bath Parameters Amounts Zinc metal 8-15 g/L Iron metal 0.05-0.1 g/L Sodium hydroxide 120-140 g/L Temperature 18-23OC Cathode current density 1.5-3.0 A/dm2 Anodes Steel Table VII. Bath Parameters for a Neutral pH Tin-Zinc Bath Parameters Rack Barrel Tin (metal) 20 g/L 10 g/L Zinc (metal) 8 g/L 10 g/L Stabilizer 120 g/L 120 g/L Antioxidant 80 g/L 80 g/L Temperature 18-25oC 18-25oC pH 6.0-7.0 6.0-7.0 Cathode current density 18.5 A/ft2 5.0 A/ft2 Anodes Tin/zinc (65/35-75/25) mixed anodes Table VIII. Sulfur Dioxide Gas Corrosion Test Tin-Zinc Alloy Ratio Zinc plating Hours to White Corrosion Hours to Red Corrosion Nonchromated 60/40 60/40 75/25 85/15 10 5 5 5 12 12 9 12 400 210 170 185 Chromated Tin-zinc alloy plating Thickness (μm) 60/40 75/25 85/15 5 5 5 20 50 50 250 400 250 5 10 12 12 200 250 Yellow Iridescent Chromated Sulfur dioxide gas concentration, 200-300 ppm; temperature, 40 ±2°C; humidity, >95%. 320

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