Investigation and optimization of effective parameters on electropolish process of stainless steel used in cryogenic reservoirs

The effect of electropolish process on the roughness and glossiness of stainless steel 316 used in cryogenic storage dewars is investigated here. A mixture of phosphoric and sulfuric acid (with 4:6, 5:5, and 6:4 volume ratios), 10% water, and 2% glycerin is prepared and subjected to electropolish process with electric current density of 0.05-0.3 A/cm2, temperature of 50-70 °C, and time of 2-30 minutes. Atomic force microscopy (AFM) is implemented for surface coating analysis. Results indicate that when the volume ratio of phosphoric and sulfuric acid is 4:6, the electric current density is 0.2 A/cm2, the temperature is 55 °C, and the time is 7 minutes, the electropolish process has the best outcome on the surface quality.