On the theory of anodic levelling: model experiments with triangular nickel profiles in chloride solution

Abstract

The influence of profile height and orientation on the rate of anodic levelling was studied under controlled masstransport conditions in a flow cell using triangular shaped profiles made of nickel in a NaCl electrolyte. Experimental conditions were chosen so that levelling was carried out well below, close to and well above the limiting current for salt precipitation and results were compared to those predicted from theoretical calculations using FEM. It is found that the rate of levelling of microprofiles under limiting current conditions is independent of flow direction and corresponds to that theoretically predicted for primary or tertiary current distribution. The levelling of macroprofiles at the limiting current is slower and depends on flow direction. Levelling above the limiting current is mass transport controlled. For macroprofiles oriented parallel to flow direction, levelling is slower above the limiting current than at the limiting current.