Galvanic Dissolution Behavior of Magnesium-1 mass percent manganese-0.5 mass percent calcium Alloy Anode for Cathodic Protection in Fresh Water

摘要

Magnesium-1 mass percent manganese-0.5 mass percent calcium (Mg-l mass percent Mn-0.5 mass percent Ca) alloy was used as sacrificial anode. This work was performed to investigate the galvanic dissolution behavior of the alloy anode for cathodic protection in fresh water. The microstructure and dissolved surface of the alloy anode were analyzed with an electron probe micro analyzer, a scanning electron microscope with energy dispersive X-ray spectrometer and a microscope. The current efficiency of the anode has been measured by laboratory test method of galvanic anodes for cathodic protection. It was found that calcium is present uniformly at the grain boundaries as Mg_2Ca or Mg-Ca-Si compounds. Calcium compounds dissolve preferentially compared to the matrix of magnesium, as a result the anode uniformly dissolve compared to Mg-1 mass percent Mn alloy anode. The current efficiency of the anode for the dissolution was higher than that of Mg-1 mass percent Mn anode. On the other hand, manganese is added in order to decrease the local cathode to magnesium alloys, however the part of manganese compounds act as the local cathode in the alloys.