Electrochemical Polishing of Tungsten: An Investigation of Critical Spatial Frequency and Ultimate Roughness

Electrochemical polishing (ECP) offers incomparable advantages and great potential in metal polishing by surface errors correction. This paper systematically investigates the ultimate roughness and surface errors correction ability of ECP over different spatial frequency ranges. This paper further explores the law of ECP influencing errors at different frequency ranges, proposes and clarifies the concept of critical spatial frequency, and studies the law of polishing parameters affecting critical spatial frequency by using spatial frequency spectrum analysis. The surface roughness evolution and ultimate roughness of ECP were investigated using the surface error filtering method based on the critical spatial frequency. The ultimate roughness of ECP was determined by two different strategies, (i) stepwise polishing and (ii) one-step polishing. In addition, the stepwise polishing was also investigated for any possible inconsistency with one-step polishing on the final surface roughness. As ECP progressed, the optimization speed of surface roughness gradually decreased, and the surface roughness eventually reached a stable limiting value. Further analysis revealed that crystal corrosion is mainly responsible for inhibiting surface roughness optimization.