To investigate the effect of impurities in solution on the lightness, surface morphology and current efficiency of deposited Ni, Ni electrodeposition was performed at a current density of 300 A/m
2 and 7.2×10
5 C•m
−2 of charge, in an unagitated chloride solution containing Mn
2+, Cr
3+ and SO
42− ions as impurity with pH 1 to 3, at 333 K. In solution containing 10 g•dm
−3 of Mn
2+, the current efficiency for Ni deposition decreased slightly, and crystal size of deposited Ni became small. The lightness of deposited Ni decreased when the concentration of Mn
2+ exceeded 1 g•dm
−3. When the Ni deposition was performed using soluble Ni anode to prevent the formation of MnO
2 at anode, the lightness of Ni was higher than that using insoluble anode, which suggesting that MnO
2 resulting from insoluble anode caused the decrease in lightness of Ni. In solution containing Cr
3+, the current efficiency of Ni gradually decreased with increasing concentration of Cr
3+, and significantly decreased above the Cr
3+ concentration of 0.1 g•dm
−3. The lightness of deposited Ni greatly decreased with increasing concentration of Cr
3+ above 0.001 g•dm
−3. In solution containing Cr
3+, it is presumed that Cr(OH)
3 formed at cathode layer suppresses the Ni deposition, resulting in some codeposition of NiO and Ni(OH)
2 with Ni, which causes the decrease in current efficiency and lightness of Ni. On the other hand, in solution containing SO
42−, the current efficiency of Ni somewhat decreased at SO
42− concentration above 50 g•dm
−3, and significantly decreased above 100 g•dm
−3. The lightness of deposited Ni somewhat increased at SO
42− concentration of 20 g•dm
−3, and greatly increased above 20 g•dm
−3. Since the overpotential for Ni deposition increases with increasing concentration of SO
42−, the surface of deposited Ni becomes smooth, resulting in increase in lightness.
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