Optimization and mechanism of SUS 304 stainless steel by electrochemical polishing

SUS 304 stainless steel is widely utilised in modern industrial applications, where high surface quality is critical for enhancing corrosion resistance, reducing friction and wear, and ensuring long-term service reliability. In this study, electrochemical polishing (ECP) of SUS 304 stainless steel was performed using a green NaCl–ethylene glycol (EG) electrolyte. Orthogonal experiments determined the optimal ECP parameters: pulse voltage of 30 V, pulse frequency of 2000 Hz, duty cycle of 30%, polishing time of 12 min, and electrode gap of 20 mm. Under these conditions, the polished surface roughness (Ra) decreased from 141 nm to 15 nm, the contact angle increasing from 73.4 ± 0.5° to 86.2 ± 0.3°, the corrosion current density decreasing from 3.081 × 10−6 A/cm² to 1.232 × 10−6 A/cm², the average Vickers hardness dropped from 365.1 HV to 227.6 HV, and the wear rate decreased from 0.0049 mm3/(N·m) to 0.0017 mm3/(N·m). A bubble-evolution and microscale mass-transfer model was established to investigate the coupling between gas evolution, electrolyte transport, and electrochemical dissolution. The findings in this work provide the advanced ECP methodology for SUS 304 stainless steel, which is particularly important for applications in biomedical devices and aerospace components.