Metal Finishing Guide Book


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Phosphoric acid, 75% Chromic acid, 6.5% Al3+ and Cr3+, to 6% Current density, 150 A/ft2 Temperature, 175-180¡F Voltage, 10-15 V 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 (AC) Nickel and Alloys Sulfuric acid, 60% minimum Chromic acid, to saturation Water, as required Sulfuric acid, 60% minimum Glycerin, 200 ml/L Water, as required Nickel sulfate, 240 g/L Ammonium sulfate, 45 g/L Potassium chloride, 35 g/L Orthophosphoric acid, 15-70% Sulfuric acid, 15-60% Water, balance STEEL Steel is more difficult to electropolish to the same degree of perfection as other 88

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