Results from a pilot cell test of cermet anodes [report]

Jr, C F Windisch, D M Strachan, Jr, C H Henager, E N Greenwell, T R Alcorn
1992 unpublished
The pilot cell test of the cermet anodes was completed in August 1991 at the Reynolds Metals Company Manufacturing Technology Laboratory, Muscle Shoals, Alabama. During this test 13 cermet anodes were evaluated. The longest time any one anode was tested was 314 h (13.1 days). During the pilot cell test, all of the anodes corroded severely as measured by both impurities in the aluminum metal and post-test analyses of the anodes. The overall dimensions of the anodes did not change much but a
more » ... nge much but a reaction layer of significant thickness was observed. observed deep within the anode In addition, electrolyte components were and resulted in significant changes in the composition and properties of the anode material. It is still unclear whether the cermet material evaluated in this work is the best choice for an 11 inert" anode. The negative results of the pilot cell test would appear to argue against using this material, but there were many deficiencies in the pilot cell test that may make this conclusion premature. These deficiencies primarily involved the failure to maintain optimal operating conditions, including alumina concentration at saturation, constant current and voltage conditions, constant anode-to-cathode distance (ACD), and constant temperature. Also, there were problems caused by the large carbon anode that was used simultaneously with the cermet anodes and mechanical fracture problems with both the anode connections and the cermet anodes themselves. In addition, the microstructure of the cermet anodes was not exactly the same as that tested previously in the laboratory; the ramifications of these differences are not certain. Despite no clear indication as to whether the cermet material would make a good candidate for an inert anode under more "ideal" conditions, the pilot cell test was successful in demonstrating that the performance of the anode is strongly influenced by either or both anode fabrication and operation. The results of this work indicate the variety of fabrication and operational considerations that need to be addressed carefully in any future testing of this • or other candidate material. At the very least, this work establishes an experimental protocol for anode fabrication, cell operation, and post-test diagnostics that would seem to be required in future testing. The work also points to some important chemical and physiological changes in the cermet material that occur during electrolysis that should be kept in mind in future tests. These changes will probably occur to a greater or lesser extent during most operations with the cermet anodes; albeit it remains to be determined under what conditions of anode fabrication and cell operation the rates of these transformations can be reduced to acceptable values.
doi:10.2172/7020102 fatcat:pnl3jycpcvfhddisfljmhuv4ji