cleaning, pretreatment & surface preparation
ELECTROPOLISHING
BY KENNETH B. HENSEL
ELECTRO POLISH SYSTEMS INC., MILWAUKEE; WWW.EP-SYSTEMS.COM
The electropolishing system smoothens, polishes, deburrs, and cleans steel, stainlesssteel, copper alloys, and aluminum alloys in an electrolytic bath. The processselectively removes high points on metal surfaces, giving the surface a high luster.
HOW IT WORKS
The metal part is immersed in a liquid media (electrolyte) and subjected todirect current. The metal part is made anodic (+) and a metal cathode (-), usually316L stainless steel or copper, is used. The direct current then flows from
the anode, which becomes polarized, allowing metal ions to diffuse throughthe film to the cathode, removing metal at a controlled rate. The amount ofmetal removed depends on the specific bath, temperature, current density, andthe particular alloy being electropolished. Generally, on stainless steel, 0.0005in. is removed in 1,500 amp-minutes per square foot. Current and time are twovariables that can be controlled to reach the same surface finish. For example,100 A/ft2 electropolished for 5 min is 500 amp-minutes; 200 A/ft2 for 21/2 minis 500 amp-minutes. Both pieces of metal would have about the same surfaceprofile. Current densities of 90 to 800 A/ft2 are used in this process dependingupon the part to be polished and other parameters. Electropolishing times varyfrom........
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