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Surface Preparation
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
Electropolishing is an electrochemical process in which the workpiece is submerged in an electropolishing electrolyte and connected to a positive terminal (cathode). As a result of the electropolishing process, the atoms are removed from the workpiece and converted to ions. Typically, oxidation takes place in the anode, and reduction occurs in the cathode by producing hydrogen. Although any metal can be electropolished, the most commonly polished metals are austenitic and martensitic stainless steels, copper, aluminum, titanium, nickel and copper alloys. The electropolishing process (see Figure 2.31) reduces surface roughness and makes the surface brighter. The other advantages of electropolishing are improving the corrosion resistance of the material, relieving stress and improving the material’s resistance against fatigue. Electropolishing does not involve abrasive materials and has a higher Health, Safety and Environment (HSE) compared to blast cleaning and provides smoother, lower-friction surfaces. In addition, electropolishing can be used as a steelwork method alternative to mechanical polishing to remove welding defects or polishing rough surfaces such as cut and rolled edges. The disadvantage of electropolishing is that very rough surface defects cannot be removed by this technique.
Motor Frame Design
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
As a reverse plating technique, electropolishing is an electrochemical process that is typically used for surface polishing and corrosion resistance enhancment. While electroplating deposits a thin metal layer on surfaces on either metallic or nonmetallic parts, electropolishing removes surface metal, beginning with the high points within the microscopic surface texture, by using a combination of chemicals rectified electrical current. As a result, surface imperfections (e.g., surface crack, burr) and embedded contaminants (e.g., rust, oxide scale) of the parts are eliminated. Electropolished parts are left in a homogenous and passive condition, which enhances surface resistance to corrosion tarnish or oxidation. These properties are especially evident on stainless steel but also found on carbon steel, brass, aluminum, copper, and inconel. Even though all these materials are more corrosion resistant, electropolishing is generally applied to stainless steel today
Cartridges, Cartridge Holders, and Their Care
Published in Maik W. Jornitz, Theodore H. Meltzer, Sterile Filtration, 2020
Maik W. Jornitz, Theodore H. Meltzer
To overcome the problems associated with mechanical polishing, electropolishing can be used. Electropolishing provides a final, high purity surface finish. In simple terms, electropolishing is the reverse of electroplating—it removes a small amount of the surface metal. This results in leveling the pits and valleys caused by the mechanical polishing and produces an even smoother surface. Electropolishing also serves to restore the chromium oxide film to passivate the surface, which lends stainless steel its high level of corrosion resistance. A low quality stainless steel surface, one that contains both surface and subsurface pits, fissures, and folds, requires mechanical finishing prior to electropolishing for the latter practice to be effective.
Natural convection mass transfer correlation of the electropolishing of horizontal cylinders with active ends
Published in Transactions of the IMF, 2021
M. A. El-Naggar, M. H. Abdel-Aziz, G. H. Sedahmed
Electropolishing of metals is an anodic metal finishing process that produces a smooth bright metal surface. Industrial applications of electropolishing are diverse,1–6 they include metal decoration, pretreatment before electroplating of metal to obtain a smooth bright electroplate, smoothing of moving machine parts to decrease friction and save energy consumption, deburring of mechanically machined workpieces, detection of surface cracks and defects in high-pressure vessels and nuclear reactors, etc. The aerospace industry uses electropolishing widely to machine hard metals and alloys which are expensive to polish mechanically owing to the high energy consumption.6 In addition, electropolishing does not leave residual stresses in the metal while mechanical machining may deform the metal and leads eventually to stress corrosion cracking.7
Electropolishing of nickel and cobalt in deep eutectic solvents
Published in Transactions of the IMF, 2018
W. O. Karim, A. P. Abbott, S. Cihangir, K. S. Ryder
Electropolishing is essentially the controlled electrochemical corrosion of a metal to bring about a decrease in surface roughness. Electropolishing an item can increase the corrosion resistance of the component as it enables better, more homogeneous passivation and it can also decrease wear in moving systems. It has most commonly been studied in aqueous solutions primarily using concentrated mineral acids such as sulphuric, hydrochloric and phosphoric acids. The large scale usage of electropolishing is most frequently applied to stainless steel1 although other metals such as nickel, copper and titanium are also electropolished.2–4 The fundamental and practical aspects of electropolishing have been covered in two reviews.5,6 It is known that for electropolishing to occur, a viscous film generally forms on the metal surface.5 It is therefore essential to choose an electrolyte that will enable film formation on the metal surface.6 This process is not free from some practical issues, such as the corrosivity of the electrolyte, gas evolution and low current efficiency.