Math Easy Solutions, DC is used because electrolysis needs the electrodes to keep the same identity the whole time: one must stay the cathode (reduction) and the other the anode (oxidation), so ions move in one steady direction and the products can actually build up Wikipedia TutorChase. With AC, the polarity flips back and forth, so the electrodes keep swapping roles and the ions reverse direction, which tends to cancel the chemistry instead of sustaining it Vedantu. Your recent thread on electrolysis is here if you want to drop that into the reply chain: @mes thread.