Abrasive-free polishing of tungsten alloy using electrochemical etching

•An abrasive-free polishing process using anodic etching is applied to tungsten alloy.•Current-driven ECP has high polishing efficiency but no flattening effect.•Potential-driven ECP can realize an ultra-smooth surface with limited efficiency.•Surface Ra roughness is reduced from 651.8 nm to 17.6 nm by two-step ECP process.

Tungsten alloy is a crucial engineering material for electrical and optical applications. However, damage-free and highly efficient polishing of tungsten has not been realized yet. We report the abrasive-free polishing of tungsten alloy using electrochemical polishing (ECP), which is an etching process. To achieve balance between polishing efficiency and surface quality, a two-step ECP process has been proposed. Current-driven ECP lasting for 3 min, as the first step, quickly removed the surface grinding marks and subsurface damage while the following potential-driven ECP lasted for 20 min, as the second step, improved the surface roughness and an ultra-smooth surface with an Ra roughness of 17.6 nm was finally obtained.