Metal Finishing Guide Book

2013

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F.) mineral-free water for about 15 minutes, dipped in a 1% aqueous ammonia solution for about 10 seconds and then rinsing again in mineral-free water before going into your plating bath. Parts may be processed in a rotating basket if so desired. Table 4 outlines the currently used process for processing cast aluminum alloys with the organic-based "Plating Catalyst" and once again the casting may, if so desired, be dried and stored in a clean dry area to be processed at a later date by once again soaking them in warm (100 -120 degrees F.) mineral-free water for about 15 minutes, dipped in 1% aqueous ammonia for about 10 seconds and then rinsing again before going into your plating bath. The parts may be processed in a rotating basket if so desired. Regardless of what aluminum alloy is being processed, the same "Plating Catalyst" used and your major source of loss is "drag out" from the bath. The very thin catalytic film (about 100 – 200 nm) is displaced out into your plating bath and will have no adverse effect upon the bath. The electrochemical deposition of the catalytic film is not directional and once the deposition process starts, the film will deposit itself in any and all recessed areas or small holes. 1. 2. 3. 4. 5. 6. 7. 8. 9. Clean in a Phosphoric acid or Sulfuric acid based cleaner at about 110 – 120 degrees F. for two to three minutes. Rinse in mineral-free water. Activate by immersion in a 5% Potassium Hydroxide solution at ambient temperatures until you have uniform and even gassing of the part, generally not more then 10 – 15 seconds. Rinse in Mineral-free Water. Acid etch in 20% sulfuric acid containing about 1.5% ammonium bifluroide for two minutes. Rinse in mineral-free water. Rinse in 1% ammonia water solution to remove all traces of acid or acid Salts for 10 – 15 seconds. Rinse in mineral-free water and go immediately directly into "Plating Catalyst" making the part the anode at about 15 - 16 amps per square foot for about two to three seconds. Rinse the part off in a 1% ammonia water solution followed by a mineral-free water rinse and take directly to the plating bath. Table 3. Procedure for the processing of wrought aluminum alloy parts by new process. 1. 2. 3. 4. 5. 6. Strong alkaline (pH of 12 or higher) cleaner at about 150 – 170 degrees F.for two or three minutes. Double rinse in mineral-free water. 1% – 3% fluoride salt added to 20% - 25% sulfuric acid with the balance being nitric acid at ambient temperatures for one to three minutes. Rinse in mineral-free water followed by a rinse in a 1% ammonia water solution to remove all traces of acid or acid salts. Rinse in mineral-free water again and go directly into "Plating Catalyze" making the casting the anode at 15 – 16 amps per square foot for two to three seconds. Rinse casting in 1% ammonia in water and mineral-free water and go directly into the plating bath. Table 4. Procedure for processing of cast aluminum parts by new process. 243

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