Electropolishing is one of the most complex techniques of electrochemical treatment of steel. The main objective of this process is to obtain smooth surface formed by reaction products. Except the basic objective of this process, i.e. smoothing the surface, a product is subjected to deep anodic passivation. Therefore, product is thoroughly secured against corrosion. The process is also applied for production of modern pipes, surfaces of which become smooth by application of this method. Electropolishing affects the extension of a system life, which fact in case of very expensive materials (acid-proof, duplex pipes) is beneficial.
Electropolishing is performed in a galvanizing bath, where a given product is being connected to a positive electrode, i.e. anode. As a result of such operation, unevenness of metal surface is covered with a thin layer of higher resistivity comparing to a given electrolyte. The process results in dissolution of metal and reduction of roughness difference between tips and valleys on a given element. Therefore, the surface becomes smooth. Electropolishing does not adversely affect the macroscopic structure of the surface or any small product details. To microscopic scale, surface of metal subjected to electropolishing becomes glossy and smooth.
Internally electropolished pipes are used in applications where the highest grade of cleanliness is required. This is especially useful in food industry, pharmacy, chemical and nuclear industry.
Grinding, as opposed to electropolishing, is a surface finishing process using abrasive tools providing low roughness. Another type of machining is polishing. It is to remove rough layer on the surface that remained after grinding. The polishing process is exceptionally labour-consuming, that is why it is only used in situations where a very low roughness of the final product is required. Contrary to electrochemical techniques, in traditional grinding and polishing, abrasive and mechanical means are necessary. Using the electropolishing, pipe surface becomes smooth by means of a current passing through it. The major effect of electropolishing is highly smooth, clean and glossy surface. It is worth of mentioning that chemical resistance of a material subjected to such technique increases even up to 20 times. Such properties cannot be achieved using traditional mechanical grinding.