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ELECTROPOLISING
Electropolishing is an effective way to passivate a stainless steel surface. This process creates a passive surface, enhancing corrosion resistance and reducing particle generation via anodic dissolution. Electropolishing removes a microscopic amount of material from the surface, forming a smooth, passivated and chromium rich surface. This must be controlled in order to achieve an ideal passive surface.
Electropolishing is the improvement in the surface finish of a metal in a suitable solution. With the proper selection of current density, temperature and other conditions, the surface is smoothened and brightened while metal is removed. Electropolishing will produce a chemically clean, lustrous-to-mirror bright surface.In fact, because it removes surface metal,electropolishing tends to displace surface inclusions arising from stamping, machiningetc. The electropolishing surface also ismore passive and decidedly more corrosion resistant than a mechanically polished surface.
In electropolishing, both micro and macro-asperities are preferentially removed.The removal or reduction of the surface micro-asperities increases surface reflectivity and reduces surface friction.Burrs may be regarded, to some degree, as asperities and during electropolishing they are dissolved at a more rapid rate than the rest of the surface. Deburring is one of the common applications for electropolishing.
Electropolishing is exceptional useful for polishing complex and convoluted parts.Because electropolishing will occur wherever the process solution contacts the work piece and the appropriate current density much more readily than they could be treated by mechanical polishing. Difficult parts can be finished by electropolishing .
The more homogeneous and fine-grained the structure of an alloy or metal is, the better the result of electropolishing will be. Because of their basic metallurgical make-up, nickel-containing stainless-steels(300 series) have a structure that is particularly well suited for electropolishingand thus constitute a large portion of the commercial applications for electropolishing.Applicants include the reduction of gearwear, and the use of electropolishing toproduce desired dimensional requirements. Electropolishing does not “flow” the metalsurface. Deep scratches or surface imperfections are not smeared over and hidden as they are by mechanical electropolishing. Because Electropolishing provides a passivating oxide film roughly 15-50 angstroms thick, it creates better corrosion resistance. In fact good passivation of the surface typically requires chromium-rich oxide thickness in the 25-40 angstrom range.
Surface smoothness is also increased.Because electropolishing is a liquid bath,it wets to surface thoroughly and better than mechanical polishing. Finally, an electropolished surface provides betterclean ability because the surface is smoother and therefore can better release chemicals, dirt and bacteria. The flatter surface is free of points, cracks and crevices where organic contamination can build up, and where stress corrosion often occurs.
One of the special features of Electropolishing is possibility of getting bright surface irrespective of roughness grade.