Harold A Robinson

Performance of Magnesium Galvanic Anodes In Underground Service

Abstract The performance of magnesium galvanic anodes in underground service is reviewed in the light of the past five years of field testing in which upwards of 2500 anodes have been tested in some 40 different backfills and in various soils. The pertinent indices of galvanic anode performance are cited and the various factors influencing the performance of magnesium anodes are enumerated. A summary of the most outstanding findings relative to anode current efficiency, anode current output and stability of current flow is presented. The effects of such factors as anode composition and impurities, current density, time, backfill composition, installation practice, soil characteristics, and weather on anode performance are discussed. The high purity Mg-6Al-3Zn alloy continues to provide the most consistently efficient performance. At current flows equivalent to ten year life, efficiencies corresponding to 500 ampere-hours per pound are usually realized except in high chloride soils where higher current den...