Some observations on manganese steel bimetallic couples from the point of view of cathodic protection

The bimetallic corrosion of electrolytic manganese-mild steel couple in seawater was studied. Results indicated that the corrosion rate of manganese follows the 'Catchment Area' principle upto anode: cathode area ratio of 1:150. Steel surface of sufficiently large area received adequate protection when galvanically contacted with manganese metal of 1.0 cm2. The solution potential of manganese was -1.25 V to SCE and showed the anode efficiency of 70-80%. The possibility of using manganese as a sacrificial anode for cathodic protection is discussed especially from the electrochemical point of view. (Shri K.P. Mukherjee, Scientist, National Metallurgical Laboratory, Jamshedpur and Shri D.K. Khan, Junior Technical Assistant, NML Marine Corrosion Research Station, Digha)