Electropolishing for Ultracleaning and Decorative Finishes
Perhaps the best known 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 is capable of removing heat tint from welding and heat treating operations. Removing heat tint and the embedded oxides from machining and polishing compounds is achieved by removing controlled amounts of material. After electropolishing, the part is clean, passive, in tolerance and ready for assembly.
An electropolished part has the following characteristics:
Unlike paints, plating or Teflon coatings, an electropolished surface does not peel or abrade. This is especially 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.
Electropolishing can provide a uniform on complex or fragile parts that do not lend themselves to conventional finishing methods. There is no effect on surface hardness and no stresses are introduced to the part.
Since electropolishing removes embedded 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.
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 surfaces generally weld more readily with less weld splatter and surface damage.
Ultracleaning Case Study: Deburring, Decontamination and More
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 customer was looking to remove surface and embedded 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 alloy 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. The part required deburring and the removal of surface and sub-surface contamination sites.
By carefully controlling material removal, all critical surfaces were completely cleaned of surface and sub-surface contamination. The amorphous layer was removed as well, exposing 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).