Metal Finishing Guide Book

2012-2013

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Table I. Plating Solutions���Cathode Current Densities Plating Bath A/ft2 Voltage 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 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) 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 fluorocarbon 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 Copper Aluminum Brass Steel Phosphor Bronze Stainless Steel (300 series) Titanium 1 1 1000 600 250 120 180 23 31 1 750 450 185 90 135 17 23 1 500 300 125 60 90 12 16 1 250 150 63 30 45 6 8 1 (dia.) 785 470 196 94 141 18 24 3 445 265 111 53 80 10 14 1 200 120 50 24 36 5 6 1 50 30 13 6 9 1 1 3 28 16 7 31/2 5 5 7 5 20 12 5 21/2 35/8 1 5 1 12 6 3 11/2 2 1 /4 3 3 7 4 1 17/8 11/4 3 /16 1 3 13/4 Size (in.) /4 /2 /4 /16 /32 /8 /32 1 /16 3 /4 1 /2 1 /2 /8 /2 1 /16 /8 /8 /8 /4 3 /32 749

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