Abstract: In order to meet the requirements of various electrolytic pickling processes，this paper designs a bipolar
pulse pickling power supply based on a two-stage inverter structure and puts forward its real-time control method．This power supply outputs DC，DC pulse，AC symmetry pulse and AC asymmetry pulse． Through the electrical characteristic analysis and the micro-morphology observation of pickling surface，the effects of pulse frequency and current density on the electrolytic pickling process under the AC symmetry pulse mode are investigated． Experimental results demonstrate that there is an optimal value of pulse frequency corresponding to current density，and the pickling process with the optimal pulse frequency achieves a high removal efficiency of oxide skin with a smooth workpiece surface，and that the pulse frequency of AC symmetry pulse has a significant effect on the pickling result，and the optimal pulse frequency increases with the current density． Therefore，the pickling efficiency and result can be improved by means of the real-time control of pulse frequency．

Key words: electrolytic pickling, variable polarity, inverters, rust removal mechanism, load characteristic