Perhaps the best know application for electropolishing is decorative finishing. This is only a small part of the story. While the bright finish is the trademark of electropolishing, the key benefits of surface cleansing are much more than a shiny appearance. Since the process removes surface metal, virtually all surface impurities are removed as well. Ultraclean parts are completely free of residual dust, embedded scale, foreign debris, oils, grinding compounds, and other materials.
Electropolishing removes heat discoloration from welding and heat treating operations. The imbedded oxides from machining and polishing compounds are removed with a controlled amount of material removal. After electropolishing, the part is clean, passive, in tolerance and ready for assembly.
An electropolished part has the following characteristics:
Non-Coating
Unlike paints, plating or Teflon coatings, an electropolished surface does not peel or abrade. This is espe¬cially important where particles from coating abrasion can cause equipment malfunction or other hazards. Typical areas include food or pharmaceutical processing, high vacuum assemblies, pure gas/water systems and critical switch assemblies.
Non-Distorting
An electropolished finish can be uniformly applied on complex or fragile parts that do not lend them¬selves to other finishing methods. There is no effect on surface hardness and no stresses are introduced to the part.
Stain/Corrosion Resistant
Since electropolishing removes imbedded impurities and smoothes a metal surface, the resulting finish is more resistant to corrosion, tarnish or oxidation. These properties are especially evident on stainless steel, but also found on carbon steel, brass, aluminum and copper. While all these alloys are more resistant, we do not routinely recommend electropolishing as a substitute for coatings designed to protect a metal part in harsh environments.
Improve Weldability
In critical spot weldments, electropolished components are more conductive. The improved conductivity allows better, stronger welds at lower voltage. In other welding or brazing operations, electropolished sur¬faces generally weld more readily with less weld splatter and surface damage.
Ultracleaning Case Study
This part is fabricated from a beryllium/ nickel alloy, used in a switch application. The ribs are cut by wire EDM, formed to shape, followed by heat treat. The cus¬tomer was looking to remove surface and imbedded contamination from both the EDM process and subsequent handling.
Under 100x and then 500x magnification, the delicate ribs show obvious contamination, burrs, and recast materials on all sides and edges. Because of the soft aloy and very critical shaping, this part did not lend itself to mechanical cleaning for fear of warping or distortion. Additionally, critical dimensions eliminated the possibility of chemical etching which often has widely varying stock removals.
By carefully controlling material removal, all critical surfaces were completely cleaned of surface and sub-surface contamination. The amorphous layer was removed as well, esxposing the true base metal. In this and similar cases, electropolished parts will pass strict clean room standards. Additionally, in high stress/high cycle switching applications, the removal of stress cracks extends product life (see case histories in de-stressing).
