Effect of electropolishing variables on the current density-voltage relationship

The effect of electropolishing variables of time, bath temperature, and composition of electrolyte on the corresponding current density-voltage potentiometric curve were studied on 1 Cr, $\text{1}\text{2}$Mo, T11 steel. Electrolytes of various percent perchloric acid solutions and a chromic-acetic acid solution were investigated due to their wide use in electropolishing. It was found that time had a minimal effect on the quality of electropolishing below 20-s durations for the perchloric acid solution and 90-s durations for the chromic-acetic acid solution when electropolishing at 25°C. Changing the temperature of the bath caused the characteristic horizontal polishing plateau at 2°C to become sloped at higher temperatures. However, there were still three distinct regions of the current density-voltage curve and correspondingly good electropolished surfaces were obtained at these higher temperatures. With an increase in the percent of perchloric acid in the electrolyte came a corresponding increase in the current density at constant voltage. The three characteristic regions were still observed, and electropolishing occurred in the middle region.