For the production of perchlorate, various anode materials have been used commercially, including smooth massive platinum, platinized titanium or tantalum (despite a tendency to produce excess oxygen) and lead dioxide coated on titanium or graphite, although these lead dioxide anodes have a high overvoltage and wear rapidly.
Some proposals have already been made to combine platinum group metals and tin dioxide in electrode coating materials. For example, U.S. Pat. No. 3,701,724 mentioned an anode for chlorine production having a coating consisting essentially of a minor amount of a platinum group metal and/or platinum group metal oxides with a major amount of SnO.sub.2, Sb.sub.2 O.sub.5, Sb.sub.2 O.sub.3 or GeO.sub.2 and mixtures thereof. However, the claims and examples of this patent are directed solely to such coatings containing platinum group metal oxides and there is no enabling disclosure of a coating containing a platinum group metal. Also, U.S. Pat. No. 3,882,002 proposed an anode for chlorine production having a valve metal substrate coated with an intermediate layer of tin dioxide which was covered with an outer layer of a platinum group metal or oxide thereof. Neither of these proposals was directed to improving electrolytic performance in the production of percompounds.