Metal Finishing Guide Book

2012-2013

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Problem Possible Cause How to Correct Poor covering power 1. Low current density 2. Poor electrical contact 3. High sulfate (low ratio) 4. High catalyst 5. High temperature 1. Increase current density 2. Ensure positive electrical contact 3. Lower sulfate (add barium carbonate) 4. Temporarily add chromic acid 5. Lower 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 1. Adjust temperature 2. Adjust current density 3. Increase chromic acid 4. Analyze and adjust sulfate 5. Adjust catalyst to within range Whitewash 1. Low sulfate 2. Low catalyst 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 nickelplated steel panels. Problem Possible Cause How to Correct Dark smudges on work 1. High pH 2. Low wetting agent 3. Low complexer 4. Low chromium concentration 1. Adjust pH 2. Add wetting agent 3. Add complexer 4. Add chromium White deposit at LCD cutoff 1. Zn, Pb contamination 1. "Dummy" solution at 15 ASF White patches on work 1. Lead contamination 2. Poor cleaning prior to nickel 3. Part dries prior to chromium plating 1. "Dummy" solution at 15 ASF 2. Improve cleaning 3. Keep parts slightly wet Poor coverage 1. Low pH 2. Low specific gravity 3. Zn, Pb contamination 4. High air agitation 5. High temperature 1. Correct pH 2. Add conductivity salts 3. "Dummy" at 15 ASF 4. Reduce air agitation 5. Reduce temperature Dark deposits overall 1. High temperature 2. High pH 3. Metallic contamination 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. 531

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