The electrolytic process is the process that proceeds when an electrical charge is put on between two electrodes in a conducting electrolyte. Some examples of electrolytic aluminium surface treatments are anodising, AC-electrolytic graining and plating. Electrolytic process is the use of electrolysis in industry to refine metals or compounds at a high purity and low cost. Some examples are the Hall-Héroult process used for aluminium, or the production of hydrogen from water. Electrolysis is usually done in bulk using hundreds of sheets of metal connected to an electric power source.