Apparatus and method for electrolytic coating of a mould, the internal surfaces of which demarcate a mould cavity, with a coating material for the purpose of achieving or re-achieving intended mould cavity dimensions. The mould, as the cathode, and an anode positioned in the mould cavity and an electrolyte containing the coating material are used. The electrolyte serving as the carrier of the coating material flows through the mould cavity in a controlled manner. During the electrolytic coating, only the internal surfaces of the mould cavity come into contact with the electrolyte and the external surfaces of the s mould therefore do not have to be covered. The mechanical properties can be kept largely uniform over the entire region. The coating can be achieved more rapidly than with the conventional processes.