Other Patented Anode Compositions

As described earlier, the DSA electrode is typically a valve metal substrate coated with a noble-metal-based composition. Either to circumvent the basic Beer patents or to achieve better and less expensive anode compositions, considerable efforts have been devoted to the development of novel anode coatings. A wide variety of compositions [14] have been described in the literature, and it is beyond the scope of this chapter to review these developments individually. A generalized formulation of anode materials can be schematically described as Sub/VM - - NM + NNM, where Sub refers to the substrate, VM to the valve metal, NM to the noble metal, and NNM to the non-noble metal. The compositions cited in the literature include the following in various combinations  

Some anode compositions are presented in Table 4.5.1 to illustrate the directions followed to develop alternate anode coatings. It should be noted that this is not a complete list and that more details are available [15-20]. 

Noble metals or thdr oxycompounds and noble-metal-based qnnels M 3/204, where Ml = Mg, In, Co M2 = Cd, Co, Ni U.S. 3,711,397 

There are thousands of patents describing various anode compositions, yet only Beer patents were commercialized. The valid patents are noted in Table 4.5.2 along with their current status. The key patents in Table 4.5.2 all have expired. 

Physical Characteristics and Morphology ofRu02 + Ti02-Based Electrodes 

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The aluminum industry consumes much more carbon, as baked anode composites, than the total of all other industrial uses for baked and graphitized carbon products. The free world s total annual aluminum production capacity is approximately 16 million short tons, about one-third being produced in the United States. World aluminum production involves the consumption (oxidation) of about eight million tons of anode carbon. Production occurs by electrolytic deposition from cryolite-alumina melts using a process patented simultaneously, but independently, in 1886 by Hall in America and Heroult in France. While minor process modifications have been made in the intervening years, and productivity greatly increased, substantially the same process is still used. The industrial electrolytic cell consists of a shallow carbon vessel about 10 ft. wide by 30 ft. long, and 1-2 ft. deep, which acts as the cathode and contains the fused salt bath and molten aluminum product. The carbon anodes are supported above the cathode and lowered into the cell at the rate of... 

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