Metal Finishing Guide Book

2012-2013

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Table VIII. Operating Parameters for Electropolishing Different Metals and Alloys Temperature C �� Metal/Alloy Anodic Current Density (A/ft2) Voltage 10-30 �� F Aluminum 150-200 66-93 10-60 Copper 65-160 18-71 20-300 6-18 Nickel 85-125 29-52 100-200 10-18 Stainless steels 110-190 43-88 50-500 6-18 Carbon steels 110-140 43-60 100-300 10-18 Titanium 60-105 16-40 80-500 3-10 rinsing is required to remove any films, or in a double cleaning cycle use an inhibited/wetted acid as the first acid, followed by a simple mineral acid as the second acid. Some modifications are made to cathodically remove heavy scales and rust. Acid dipped or pickled parts should be free of any organic soils, rust, scale, and smuts. This is the last process treatment bath before plating, painting, chromating, or final topcoat application. ADDITIONAL CLEANING OPERATIONS Electropolishing This is an electrolytic process by which the substrate���s surface can be improved using a specific solution. Burrs, belt lines, scratches, scales, and other imperfections anywhere on the surface that is immersed and anodically charged will be polished and refined. Electropolishing is current-density specific. In this regard surface improvement occurs more readily than by mass finishing. A wide variety of common metals and alloys are successfully electropolished, especially the nickel-rich 300 series stainless steels. The electrolyte is typically a mixture of mineral acids. Parts are predominantly racked. The ranges in the operating parameters shown in Table VIII reflect the use of more than one type of electrolyte. Table IX. Liquid and Powder Spray Cleaner Operating Parameters Temperature Cleaner Type Concentration Range �� F �� C Time (min) Agitation Liquid 2-5% v/v 100-160 38-71 0.5-3 15-35 psi Powder 3-6 oz/gala 100-160 38-71 0.5-3 15-35 psi a 22.5-45 g/L Table X. Spray Cleaner Operating Parameters���Bath Chemistry (oz/gal) Metal Aluminum Caustic Silicate Complexor Phosphate Glycols Wetters ��� 0.05-0.1 0.08-0.12 0.10-0.17 0.10-0.14 0.06-0.09 Steel 0.4-0.8 0.3-0.6 0.10-0.14 0.10-0.17 0.10-0.14 0.06-0.09 Stainless steel 0.4-0.8 0.3-0.6 0.10-0.14 0.10-0.17 0.10-0.14 0.06-0.09 Brass 0.0-0.06 0.3-0.6 0.12-0.17 0.2-0.4 0.10-0.14 0.06-0.09 Copper 0.0-0.17 0.15-0.3 0.12-0.17 0.2-0.4 0.10-0.14 0.06-0.09 Zinc ��� 0.3-0.6 0.12-0.17 0.1-0.2 0.10-0.14 0.06-0.09 White metal ��� 0.3-0.6 0.12-0.17 0.1-0.2 0.10-0.14 0.06-0.09 The cleanliness criteria are the same as described in the soak cleaning section. 158

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