Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 380 of 707

Alzac Process: First Stage (Brightening) Fluoboric acid, 2.5% Temperature, 85° F Voltage, 15-30 V Current density, 10-20 A/ft2 The polarized film is stripped in hot alkaline solution. Anodizing, as usual, in the sulfuric acid bath follows. Only superpurity alloys (99.95%) should be used. Polishing and brightening are obtained in concentrated acid-type solutions that feature greater stock removal and greater smoothing. Battelle Sulfuric acid, 4.7% Phosphoric acid, 75% Chromic acid, 6.5% Al3 + and Cr3 +, to 6% Current density, 150 A/ft2 Temperature, 175-180° Voltage, 10-15 V F Chromic acid decreases the etching rate, but changes from the hexavalent to trivalent form in use. Sulfuric acid drops the cell resistance or voltage, but increases the etching rate. Copper and Alloys R.W. Manuel Water, 100 parts by wt Chromic acid, 12.5 parts by wt Sodium dichromate, 37.5 parts by wt Acetic acid, 12.5 parts by wt Sulfuric acid, 10.0 parts by wt Current density, 250-1,000 A/ft2 Temperature, 86° F H.J. Wiesner Sodium tripolyphosphate, 14-16 oz/gal Boric acid, 4-5 oz/gal pH, 7-7.5 oz/gal Temperature, 125-135° F Current density minimum, 100 A/ft2 S.B. Emery Ammonium phosphate, 100 parts Citric acid, 100 parts Potassium phosphate, 25 parts Water, 1,000 parts Voltage, 6-25 V Current density, 75-575 A/ft2 Nickel and Alloys 379 (AC)

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