الفهرس 
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Abstract
Electropolishing is an electrochemical process that polishes a metal surface by removing a microscopic amount of material from a metallic work piece by passage of electric current. It is known as electrochemical polishing or electrolytic polishing. It is often described as the reverse of electroplating. In a plating system, metal ions are deposited from the solution onto the work piece while in electropolishing the metal ions removed from the work piece. The quantity of metal which removed from the work piece is proportional to the amount of current applied and time [1]. Electropolishing may include surface leveling and/or surface brightening. Although these terms are often used interchangeably, leveling is typically associated with smoothing of surface features larger than one micrometer while brightening shows features smaller than one micrometer. However, investigator have proposed a variety of processes to be critical to electropolishing, including formation of a viscous film at the electrochemical interface, dynamic effects related to the closeness of this film to its solubility limit, and solution-phase acceptor species for the dissolving metal ions[2].
The advantages of this process include: (1) Removal of material from the surface without introducing plastic deformation and residual stresses. (2) Removal of edge burrs and unstable oxides. (3) Soft metals, which are otherwise difficult to grind and polish, can be processed. (4) Articles with small dimensions and complex geometries can be polished. (5) Improvement of the appearance and reflectivity. (6) Improvement of passivation and corrosion resistance [1, 3].
Electropolishing also has several drawbacks, including: (1) Difficulties in polishing multi-phase materials because of different material removal rates. (2) Some features, including edges and micro-cracks, might change shape and/or expand. (3) Many solutions currently in use are toxic, or require special treatment procedures [1].
1.2. The electropolishing basics
Typically, in electropolishing, the metal work piece is immersed in a temperature controlled bath of electrolyte and connected to the positive terminal (anode) of a DC power supply, the negative terminal being attached to the cathode. A current passes from the anode, where metal on the surface is oxidized and dissolved in the electrolyte, to the cathode. At the cathode, a reduction reaction occurs, which normally produces hydrogen. Electrolytes act as a conductor to allow metal ions to be removed from the part and maintain the dissolved metals in solution. Electrolytes are most often concentrated acid solutions having a high viscosity, such as mixtures of sulfuric acid and phosphoric acid. Other electropolishing electrolytes reported in the literature includes mixtures of perchlorates with acetic anhydride and methanolic solutions of sulfuric acid. Often, the size, position and distance of the cathode to the work piece are controlled during the process in order to achieve the desired level of polish and to localize areas of polish [1].
To achieve electropolishing of a rough surface, the protruding parts of a surface profile must dissolve faster than the recesses. This process, referred to as anodic leveling.