Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Problem Poor covering power Possible Cause 1. Low current density 2. Poor electrical contact 3. High sulfate (low ratio) 4. High catalyst 5. High temperature HCD burn uniform in shape, not patchy 1. Low temperature 2. Current density too high 3. Chromic acid too low 4. Low sulfate (high ratio) 5. Low catalyst Whitewash 1. Low sulfate 2. Low catalyst How to Correct 1. Increase current density 2. Ensure positive electrical contact 3. Lower sulfate (add barium carbonate) 4. Temporarily add chromic acid 5. Lower temperature 1. Adjust temperature 2. Adjust current density 3. Increase chromic acid 4. Analyze and adjust sulfate 5. Adjust catalyst to within range 1. Analyze and adjust sulfate 2. Adjust catalyst to within range Hexavalent Chromium–Mixed Catalyst: Panels are usually plated at 5 amps for 2 minutes on nickel- plated steel panels. Problem Dark smudges on work Possible Cause 1. High pH 2. Low wetting agent 3. Low complexer 4. Low chromium concentration White deposit at LCD cutoff White patches on work 1. Zn, Pb contamination 1. Lead contamination 2. Poor cleaning prior to nickel 3. Part dries prior to chromium plating Poor coverage 1. Low pH 2. Low specific gravity 3. Zn, Pb contamination 4. High air agitation 5. High temperature Dark deposits overall 1. High temperature 2. High pH 3. Metallic contamination How to Correct 1. Adjust pH 2. Add wetting agent 3. Add complexer 4. Add chromium 1. "Dummy" solution at 15 ASF 1. "Dummy" solution at 15 ASF 2. Improve cleaning 3. Keep parts slightly wet 1. Correct pH 2. Add conductivity salts 3. "Dummy" at 15 ASF 4. Reduce air agitation 5. Reduce temperature 1. Adjust temperature 2. Adjust pH 3. "Dummy" solution at 15 ASF Trivalent Chrome (Sulfate Chloride System): Panels are usually plated at 5 amps for 2 minutes on nickel-plated steel panels. 469

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