Magnesium is an active metal, and its electrochemical properties are greatly influenced by impurities and alloying elements. When it contains a small amount of impurities, especially those with a low overpotential for hydrogen evolution, it increases the magnesium's self-dissolution tendency and reduces the current efficiency. Some impurity elements in magnesium, such as Fe, Co, and Mn, are solidly dissolved in the magnesium matrix as pure elements.