Abstract
The electrochemical performance of three sacrificial anode materials, an indium activated aluminum alloy from two distinct manufacturers and the MIL-A-18001 zinc alloy, was evaluated in several types of simulant shipboard sewage collection, holding and transfer (CHT) tank fluid environments. The preliminary results from the short-term, two week exposure tests indicated reasonable electrochemical performance in the aerated CHT fluids relative to performance results previously seen in substitute ocean water. The sacrificial anode materials exhibited slightly more electropositive potentials in the CHT environments which are still adequate for cathodic protection of steel at holidays in the organic barrier coated CHT tanks. The Faradaic efficiency values (amp hour per unit weight) were also found to be somewhat less than those previously observed in substitute ocean water. The Faradaic capacity of the indium activated aluminum alloys remained approximately 3 times that of zinc. Only slight differences were observed between the two aluminum materials depending on the type of CHT fluid involved. The tests demonstrated that the indium activated aluminum alloy should be satisfactory in the protection of CHT tank walls and indicated that the long-term performance demonstrated in full strength sea water should also be observed in the CHT fluids.
