Zinc-steel polarity reversal. I. Effect of bicarbonate concentration and temperature

The open circuit potentials of 2 types of zinc and mild steel were followed with time in different NaHCO3 solutions [10-5-10-1 M] at different temperatures [25-80 degree]. No potential reversal of polarity was observed between zinc and mild steel at room temperature. At higher temperatures, passivation of zinc and mild steel would preferentially occur, and potential reversal was manifested, particularly for pure zinc. Impurities, even in minute amounts, enhanced the activation of zinc, as well as sodium hydroxide at adequate concentration even in presence of the bicarbonate. AES survey analysis of the electrode surface gave more insight on the corrosion products