Effect of Anodic Treatment Modes in Electrolytes on Metal Removal and Current Efficiency

The effect of anode modes (electrochemical, switching, electrolyte-plasma) in the treatment of AISI 321 steel in an aqueous solution of ammonium sulfate with a concentration of 5 %, which is widely used in the practice  of electrolyte-plasma treatment of corrosion-resistant steels, on metal removal, current efficiency and specific energy spent, has been established. The greatest metal removal is observed at the border of the electrochemical and switching modes, as well as in the area of the switching mode. Depending on the electrolyte temperature, the maximum removal in this case exceeds the values corresponding to the electrolyte-plasma mode by 6–8 times. In the region of voltage values corresponding to the electrolyte-plasma mode, the coefficient of metal current efficiency h is significantly higher than at voltage values corresponding to electrochemical and switching modes. Depending on the electrolyte temperature, the values of h are in the following ranges: in electrolyte-plasma mode – 0.40–0.62; in switching – 0.18–0.24; in electrochemical – 0.16–0.24. In the electrolyte-plasma mode (210–330 V), the maximum coefficient h is provided in the region of the electrolyte temperature range of 70–80 °С. The electrolyte-plasma mode is characterized by high energy consumption per unit mass of removed metal (q/Dm) compared to the electrochemical mode. So, at a temperature of 80 °C in the electrochemical mode in the voltage range of 10–70 V, the parameter q/Dm takes values of 0.04–0.31 W·h/(cm²·mg), and in an electrolyte-plasma mode (120–330 V) – – 0.14–0.50 W·h/(cm²·mg). At a temperature of 90 °C in the electrolyte-plasma mode, the value of the parameter q/Dm varies from 0.26 to 0.63 W·h/(cm²·mg). The obtained results are the basis for creating effective complex processes for improving surface quality and dimensional treatment, in which both electrolyte-plasma and electrochemical modes are combined in one stage. This treatment scheme allows to take advantage of each of the anode modes: intensive metal removal at low energy consumption in the electrochemical mode and polishing the surface with the achievement of high surface quality in the electrolyte-plasma mode.

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