Pattern selection induced by electroconvection in the electrodeposition ofiron

The morphology of iron electrodeposit is shown to relate closely to the pH of the electrolyte solution. Macroscopically, depending on the strength of the interbranch convection, which is associated with the concentration of H 3O+ in the electrolyte, the deposit morphology varies from treelike pattern to meshlike pattern and dense-branching morphology. Microscopically the de posit is ramified and dense-branching at lower concentration of H3O+, while it becomes relatively smooth and stringy at higher H3O+ concentration. The symmetry of the convective vortices on the two sides of the growing tip is observed to decide the growth behavior of the tip. We suggest that H3O+ in fluences the pattern formation and pattern selection in the electrodepositi on of iron from FeSO4 solution by either initiating interbranch convection or changing the effective interfacial energy of the deposit and the electro lyte.