A variety of materials have been tested and used as chlorine anodes in electrolytic cells
In the past. the material most commonly used for this purpose has been graphite
However. the problems associated with the use of graphite anodes are several
The chlorine overvoltage of graphite is relatively high. in comparison for example with the noble metals. Furthermore
in the corrosive media of an electrochemical cell graphite wears readily. resulting in substantial loss of graphite and the ultimate expense of replacement as well as continued maintenance problems resulting from the need for frequent adjustment of spacing between the anode and cathode as the graphite wears away
The use of noble metals and noble metal oxides as anode materials provides substantial advantages over the use of graphite. The electrical conductivity of the noble metals is substantially higher and the chlorine overvoltage substantially lower than that of graphite
In addition. the dimensional stability of the noble metals and noble metal oxides represents a substantial improvement over graphite. However. the use of noble metals as a major material of construction in anodes results in an economic disadvantage due to the excessively high cost of such materials.