Mechanism study of electropolishing from the perspective of etching isotropy

Abstract

Electropolishing, as a damage-free and highly efficient surface finishing method, has been widely used for finishing of metal components. In this study, the electropolishing mechanism of tungsten in the electrolyte with H2SO4 and CH3OH was investigated from the perspective of etching isotropy. The anodic dissolution behavior of tungsten demonstrated that anisotropic and isotropic etching occurred under the activation polarization and mass transfer polarization, respectively. The evolution of surface morphology, roughness, and electric current density during electropolishing has been experimentally investigated and analyzed. According to the changes in surface morphology and current density, there was a transformation from anisotropic etching to isotropic etching during the electropolishing due to the time-consuming accumulation of reactive products. The application of a pulse power supply with a duty cycle of 10% resulted in a rough surface on tungsten due to the mass transfer polarization being inhibited. Similar results were also obtained in the electrolyte with 2 wt% NaOH. The presented findings experimentally demonstrate the importance of the isotropic etching mode for electropolishing, which is of great value for further revealing the electropolishing mechanism.