Various embodiments herein relate to methods and apparatus for electroplating cobalt on a substrate. In many cases, the cobalt is electroplated into recessed features. The recessed features may include a seed layer such as a cobalt seed layer. Electroplating may occur through a bottom-up mechanism. The bottom-up mechanism may be achieved by using particular additives (e.g., accelerator and suppressor), which may be present in the electrolyte at particular concentrations. Further, leveler, wetting agent, and/or brightening agents may be used to promote high quality plating results. In various embodiments, the substrate is pre-treated to remove oxide (and in some cases carbon impurities) from the seed layer before electroplating takes place. Further, the electrolyte may have a particular conductivity to promote uniform plating results across the face of the substrate.