Anodic dissolution of iron in acidic chloride solutions

The dissolution of iron in acidic chloride solutions was studied by both rotating disc and impedance techniques. Two regions of different slope were observed in the Tafel graphs after the effects of diffusion were eliminated. The Tafel slope was seen to change from ca. 44 to ca. 85 mV/decade at more positive potentials. The lower slope was confirmed by impedance measurements. An electrode reaction sequence is proposed for the dissolution reaction in the region where the Tafel slope is ca. 44 mV/decade.The addition of decylamine reduced the rate of the dissolution reaction, but the form of the polarization curves and the mechanism of dissolution remained unchanged. It was also established that decylamine is not involved in the electrode reaction of the dissolving polycrystalline iron.