Electropolishing of surfaces: theory and applications

Abstract

Electropolishing is the electrochemical process to remove the metallic material from the workpiece, in order to obtain a smoother metal surface. It has found vast engineering applications in many fields, such as food, medical, pharmaceutical and semiconductor industries. This review is aimed to provide the readership with insightful understanding of the electropolishing process, from the fundamental aspects as well as from the application aspects. The general aspects of electropolishing, including its definition, the classic setup, the fundamentals behind it and methods used to evaluate the electropolishing finishes are reviewed here. Various electropolishing theories, be them quantitative or qualitative are briefly discussed. Based on those theories, important parameters evolved in the electropolishing process are enumerated. Many microscopic technologies are used to evaluate the electropolishing surface finishes. This includes optical microscope, electron microscope and atomic force microscope. Some key features of electropolishing are briefly outlined in the end.

Polycrystalline and Single‐Crystal Cu Electrodes: Influence of Experimental Conditions on the Electrochemical Properties in Alkaline Media

“…Thus, since the peak at 0.1 V is not apparent on these electrodes and the CVs are rather similar to those obtained on the Cu(1 0 0)‐UHV electrodes, (which are shown to be free of oxide by XPS and STM), we assume that electropolishing does not remove the native oxide completely. Applying a sequence of mechanical polishing followed by electropolishing, is also consistent with the general procedure to prepare smooth metal surfaces described in detail in the comprehensive reviews for EP of metal surfaces by Landoldt and Yang et al . The procedures described in the reviews by Landoldt and Yang et al., are, however, primarily addressing leveling of rough polycrystalline surfaces.…”

“…Applying a sequence of mechanical polishing followed by electropolishing, is also consistent with the general procedure to prepare smooth metal surfaces described in detail in the comprehensive reviews for EP of metal surfaces by Landoldt and Yang et al . The procedures described in the reviews by Landoldt and Yang et al., are, however, primarily addressing leveling of rough polycrystalline surfaces. To the best of our knowledge, the literature lacks any guidelines for producing Cu single crystal electrodes with atomically well‐defined crystallographic orientation on a micrometer scale.…”

“…To the best of our knowledge, the literature lacks any guidelines for producing Cu single crystal electrodes with atomically well‐defined crystallographic orientation on a micrometer scale. In addition, there is still a huge debate in the literature whether or not a passivating film or oxide structures are formed during the electropolishing process, which might prevent perfect leveling of the surface . Furthermore, we speculate that during the electropolishing of an as received or air stored non‐mechanically polished Cu electrode, two processes are competing; 1) electrochemical oxidation of the surface Cu atoms, where the Cu ions are dissolved by an electrochemical process in the electrolyte (fast) and 2) chemical dissolution of Cu‐oxides, which does not require potential because Cu is already present in its oxidized state (slow).…”

“…The potential was controlled with a power supply (EA Elektro‐Automatik EA‐PS 7016‐10 A) and was set at the point just prior to the onset of bubble formation on the electrode, which would be related to the oxygen evolution reaction (OER) on the electrode. Performing the electrolysis at a more positive potential leads to pitting and restructuring of the surface, which can be observed with the naked eye . The electrodes were electropolished for 90 s unless otherwise mentioned.…”

Electropolishing of Laser Powder Bed-Fused IN625 Components in an Ionic Electrolyte

“…There could be easier ion transport through the salt layer because of the higher electrical field across this layer. The concentration gradient of the metal ions across the salt layer decreases after passing the voltage of the i peak region, resulting in a drop in the current density value [19]. Afterwards, the concentration gradient of metal ions increases to the V-plateau current density level and becomes saturated and constant through the plateau region.…”