Electrode cap with integral tank cover for acid mist collection

In a tank confined electrolysis process, such as electrowinning or electrorefining, having circulated electroplating solution containing sulfuric acid, a multi-element cover system is applied below the electrode conductor connections and above the surface of the electrolyte bath. This cover is evacuated in the interstices below the cover and above the bath at a rate exceeding the stoichiometric ratio causing any leakage to occur into the volume overlying the bath thereby preventing acid aerosol from escape. The rate of evacuation is restricted so that humidity is maintain under the cover and over the surface of the bath to prevent the formation of crystals formed from aerosol droplets which become supersaturated. In a preferred embodiment, a circular weir in combination with gas discharge over the weir to a downcomer is disclosed. Entrainment of air over the weir and into the downcomer is disclosed to provide sufficient pumping for evacuation.