Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 378 of 707

SUMMARY OF UNIQUE QUALITIES AND BENEFITS Stress relief of surface Removes oxide Passivation of stainless steel, brass, and copper Superior corrosion resistance Hygienically clean surfaces Decarbonization of metals No hydrogen embrittlement No direction lines Low-resistance welding surface Reduces friction Both polishes and deburrs odd-shaped parts Radiuses or sharpens edges depending upon rack position Reduces annealing steps SIMPLICITY OF THE SYSTEM Practically speaking, three major process steps are necessary to electropolish most metal surfaces successfully: 1. Metal preparation and cleaning 2. Electropolish (electropolish drag-out rinse) 3. Posttreatment (rinse, 30% by volume of 42° deionized hot water rinse) EQUIPMENT NEEDED FOR ELECTROPOLISHING Electropolishing Tank The electropolishing tank is generally constructed of 316L stainless steel, double welded inside and out. Stainless steel can withstand high temperatures, which are needed if too much water enters the elec- trolyte. Polypropylene usually 3/4 to 1- in. thick, is another tank choice. This tank can withstand temperatures of 180-190° F. The direct current source is called a rectifier. The rectifier is generally matched to the size of the electrop- olish tank. If the tank is to be cooled by tap water through a plate coil, no more than 5.0 A/gal should be used, therefore, in a 500-gal tank, the capacity of the rectifier should not be more than 2,500 A. If 3,500 A are Power Supply Baumé nitric acid, rinse, Chemicals • Equipment Process Technology for Electropolishing • Pre-Mixed Electrolytes • Technology for Large Vessels • Pipe and Tube Polishing Machines • Automatic and Manual Process Equipment • Waste Treatment Systems • Laboratory Facilities for Sample Parts • Information Seminars Metal Coating Process Corporation 204 East Jefferson Street • Monroe, NC 28112 Tel: 704-283-5738 • Fax: 704-283-5978 Email: 377

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