Zn–Mn alloy coatings were galvanostatically deposited from an acidic chloride bath at pH 2·0 and 4·9. Effects of pH on nucleation mode, surface morphology and corrosion resistance of Zn–Mn coatings were studied. Analysis of current-time transients indicated that the nucleation mode of Zn–Mn coatings at pH 2·0 is instantaneous. With increasing the pH to 4·9 at potentials of −1·08 and −1·59 V, the experimental data were observed to be near the theoretical instantaneous nucleation, but at higher potentials of −1·12 and −1·2 V, the progressive mode of nucleation was dominant. From AFM images, the average nuclei density N values for Zn–Mn deposition at pH 2·0 and 4·9 were 9·2×109 and 10×109 cm−2 respectively. At pH 2·0, this value was near that obtained by the model, but it was found to be far away at pH 4·9. Potentiodynamic polarisation indicated that the corrosion resistance of Zn–Mn coatings at pH 4·9 is slightly improved.
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