Simple and green electropolishing on drill bits by saline solution

This work examines the influence of NaCl-based polar electrolytes on the surface finishing and edge preparation of conventional drill bits via the electrolytic polishing process. Given the desire for environmentally friendly approaches within industry and the overuse of H₂SO₄/H₃PO₄ mixtures in electrochemical machining by many researchers, a non-toxic and acid-free electrolyte containing table salts was developed to deburr the surface of high-speed steel and tungsten carbide cutting tools in this study. From preliminary observations, the NaCl/ethylene glycol/ethanol shows potential in reducing the surface roughness of the tools in comparison with sulfuric acid-based electrolytes. Also, the impact of adding ethanol into the NaCl-based electrolyte resulted in suspension-like by-products was analysed with our proposed mechanism via data from EDS, UV-vis, Raman and ICP analysis. Aside from the current-voltage relationship observed by the potentiostats, the topographies and composition of the electropolished surfaces were characterised by FESEM, 3D-profilometer, XRD and XPS. Via coupling a low DC voltage with a low-cost experimental setup, this electropolishing method demonstrates a cheap, tailorable method for controlling surface roughness, which may hold value as a surface preparation step for other coating techniques such as thermal spray.