An electroplating apparatus for electroplating metal on a substrate includes a plating chamber configured to contain an electrolyte, a substrate holder configured to hold and rotate the substrate during electroplating, an anode, and an azimuthally asymmetric auxiliary electrode configured to be biased both anodically and cathodically during electroplating. The azimuthally asymmetric auxiliary electrode (which may be, for example, C-shaped), can be used for controlling azimuthal uniformity of metal electrodeposition by donating and diverting ionic current at a selected azimuthal position. In another aspect, an electroplating apparatus for electroplating metal includes a plating chamber configured to contain an electrolyte, a substrate holder configured to hold and rotate the substrate during electroplating, an anode, a shield configured to shield current at the periphery of the substrate; and an azimuthally asymmetric auxiliary anode configured to donate current to the shielded periphery of the substrate at a selected azimuthal position on the substrate.