Metals are crystalline structures with relatively large grain boundaries and thus when looking closely as such surfaces these should be evident. Mechanically manipulated surfaces do not allow us to see the surface clearly and entrap multiple contaminants out of sight. Even when looking closely at raw mill pickled plate, it is easy to see the crystalline structure Fig 1.

When the surfaces are mechanical treated to the desired level, whether that be 120, 240, 380, 400, 600 grit or mirror polished with mops they do not expose the true material and often have undesirable inclusions and contaminants. Fig 2 shows a 400 grit mechanically treated surface under 650 x magnification. This surface already is in abundance with contaminants and a perfect site for pyrogens (Germs) to grow. The roughness, especially the micro attracts the adhesion of small molecules. In service the surface would allow contaminants and substances to build, fester and create local entrapments growing exponentially to levels that affect the overall performance of the end product whether it be a surgical implant, polymer reactor, heat exchanger, or liquid / gas conveyance lines.

When the surface is taken all the steps to a full mirror polish, the surface is perceived to be clean. On close examination, the surface does not show its natural crystalline structure and in fact shows a contaminant that has been dragged in by the mechnical mop.

When the surface as shown in Fig 2 has been optimised by the electropolishing process a full crystalline structure is apparent. The upper damaged layers of material have been removed and lower undisturbed layers exposed. The material can now perform to its full potential, leading to a trouble free, low maintain service life of whatever component the original material has been specified for.