Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 617 of 707

material to be plated, its surface condition, and the surface contaminants will vary considerably, so it is necessary to engineer a more flexible pretreatment sec- tion, one capable of handling at least most of the conditions that might be encountered. For this, the following sequence might be designed: 1. Vapor or spray degreasing. 2. Alkaline soak. 3. Rinse. 4. Electroclean (cathodic or anodic). 5. Rinse. 6. Electroclean (cathodic or anodic). 7. Rinse. 8. Electropolish (i.e., 50% phosphoric acid). 9. Hot rinse. 10. Acid activation (i.e., 10% sulfuric acid or 25% fluoboric acid). 11. Rinse. 12. Strike or plate. In some processes, additional tools may be required to assist in removing par- ticularly heavy soils and oxides. These include chemical etches, mechanical brushing, and periodic reverse or pulsed electrocleaning. Plating Cycles Recommended for Specific Metals (Rinses Not Indicated) Phos Bronze/Beryllium Copper 1. Degrease. 2. Alkaline electroclean (anodic). 3. Electropolish—optional (50% phosphoric acid). 4. Acid activate (40% fluoboric acid or 20% sulfuric acid). 5. Strike (avoid immersion plating). 6. Plate. Nickel/Nickel Alloy 1. Degrease (may not be required). 2. Alkaline electroclean (anodic). 3. Electropolish. 4. Activation (20% fluoboric acid cathodic, or proprietary activators). 5. Strike (low metal, high conductivity, high current density). 6. Plate. Ferrous Nickel Alloys (i.e., 52 NiFe, Kovar) Same cycle as for nickel except activation may be accomplished in 50% hydrochloric acid. Stainless Steels 1. Degrease. 2. Alkaline electroclean (cathodic). 3. Activation (50% hydrochloric acid, 6 V cathodic). or 3. Activation (Woods nickel strike—anodic 4-6 V). 4. Woods nickel strike (40-50 A/ft2 ). 5. Strike. 6. Plate. 616

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