Electropolishing is the process of smoothing and/or brightening a metal surface anodically in a concentrated solution.
The process selectively removes high points on metal surfaces, giving the surface a unidirectional pattern that is both stress and occlusion free, resulting in a brilliant "mirror like" appearance. The surface is microscopically smooth and devoid of hydrogen. This key feature is ideal for parts that are used for medical, pharmaceutical and food processing equipment.
The result of Electropolishing is shown in the diagrams to the left which show the effect on the surface leveling of the metal: Improved surface profile, stress relieved part, and contaminant free surface.
To the right is an example of start to finish results of Electropolishing. The left product is a raw stainless steel part. The right product is the after Electropolished result.
Passivation is the removal of exogenous iron or iron compounds from the surface of a stainless steel by means of a chemical dissolution, most typically by a treatment with an acid solution that will remove the surface contamination but will not significantly affect the stainless steel itself. Passivation is the chemical treatment of a stainless steel with a mild oxidant, such as a nitric acid solution for the purpose of enhancing the spontaneous formation of the protective passive film.