ELECTROLYSIS OF ACIDIC NACL SOLUTION WITH A GRAPHITE ANODE-.I. GRAPHITE ELECTRODE

A graphite anode evolving chlorine from a chloride solution is slowly oxidized to CO and CO2. This oxidation causes a change in the characteristics of the electrode-an ageing, comprising a change of the nature of the graphite surface and an increase of the surface area. It appears that a new graphite electrode is covered with a stable oxide that protects it against attack. During continued anodic polarization this stable oxide disappears at a potential of 1·72 V, probably with formation of CO and/or CO2. The roughness of the surface then increases, attaining a maximum value of about 17 times that of a new graphite electrode, which has a roughness factor of 30. The electrochemically active surface areas of a new and of a 2000-h aged graphite electrode are 2 and 33 times the geometrical surface area respectively. © 1969.