Abstract
Extensive research work on magnesium alloy anodes has produced a new high potential material which will deliver from 20–30 percent more current to a polarized cathode than the conventional alloy anodes presently employed. Data obtained from these tests further indicate that this new anode exhibits marginally less current efficiency in normal soils when compared with Grade A Mg-6 percent Al, 3 percent Zn alloy, whereas, in saline environments the ampere-hour recovery from this high potential anode is equal to or greater than that obtained from Grade A magnesium alloy. Polarization characteristics and corrosion patterns observed with the new anode are comparable to those seen on the conventional Mg-6 percent Al, 3 percent Zn alloy.
A comparison of microstructures from commercial magnesium and the new alloy offers a possible mechanism explaining the superiority of this new material as a sacrificial anode. This is based on the coating of impurity particles with manganese rendering them less harmful as contaminants.
Field data presented by cooperating companies verify the claimed current output advantage of the new high potential anode when measured against a polarized cathode, and demonstrate the dependence of the incremental advantage on the cathode-to-soil solution potential. The economics of cathodic protection using galvanic anodes favor the use of the high-potential anode in almost all applications. 5.2.2
