Dendritic Formation and the Effects of Addition Agents in the Electrodeposition of Copper from Acid Sulphate Solutions

Summary

Work reported earlier¹ for dilute sulphate solutions has been extended to a more concentrated value (0·7M CuSO₄ containing 1·5M H₂SO₄) and the effects of thiourea and benzotriazole addition agents examined in conditions of turbulent motion. The incidence of powdery or dendritic deposits has been related to a transition from charge transfer to mass transfer control of electrodeposition, which for copper is thought to take place at currents of about 0·4 I_L. I_L is the limiting current density. However, in practice when thin finite deposits are examined the transition may appear at greater values, for instance 0·7 I_L. The mass transfer behaviour remains essentially the same at all conditions of turbulent electrodeposition.