Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Table I. Plating Solutions—Cathode Current Densities Plating Bath Brass Cadmium Chromium (decorative) Chromium (hard) Copper (sulfate) Copper (fluoborate) Copper (cyanide) Gold (acid) Nickel Silver Tin (fluoborate) Tin (stannate) Tin (sulfate) Zinc (cyanide) Zinc (low cyanide) Zinc (acid noncyanide) A/ft2 5-20 5-50 100-200 200-500 15-50 15-50 20-60 10-30 20-100 5-30 25-150 30-100 10-40 10-90 20-80 20-80 Voltage 2-5 2-5 4-6 5-12 1-4 1-4 2-5 5-6 4-8 0.5-2 1-3 4-6 1-4 1.5-6 1.5-6 1.5-6 Areas around the edge of large flat surfaces tend to plate more heavily than the center section. Edges will be exposed to higher current density. Parts with sharp points might require special care to prevent burning. In some cases, auxiliary anodes are needed so that the plating deposit remains consistent and uniform within the plating specifications. Auxiliary anodes can reduce plating time by throwing a deposit into hard-to-reach areas requiring less plating time. Whenever an auxiliary anode is needed, special care should be taken in construction to make sure that it does not come in contact with the cathodic section of the rack. A nonconductive material is used to separate the anode and cathode sections. The material most commonly used is a fluorocar- bon plastic because it can withstand the curing process. Polypropylene blocks can be used and added as a finishing operation. Table II. Chart of Relative Conductivity Size (in.) 1 1 1 1 1 1 (dia.) 3/4 1/2 1/4 3/16 5/32 1/8 3/32 1/16 654 Copper Aluminum Brass 1000 750 500 250 785 445 200 50 28 20 12 600 450 300 150 470 265 120 30 16 12 6 /4 250 185 125 63 196 111 50 13 7 5 3 74 1 313 3/4 Stainless Steel Steel Phosphor Bronze (300 series) 120 90 60 30 94 53 24 6 180 135 90 45 31 21 11 17 /2 /2 /2 /8 1/2 141 80 36 9 5 35 11 /8 2 /4 1/2 23 17 12 6 18 10 5 1 5/8 1/2 1/4 3/16 1/16 Titanium 31 23 16 8 24 14 6 1 7/8 5/8 3/8 1/4 3/32

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