塩水環境下における純マグネシウムの腐食挙動に及ぼす不純物の影響

Abstract

Various amount of impurity element such as Fe, Ni and Cu were added to 99.99% purity magnesium, and the samples were remelted in a vacuum high frequency induction furnace. The corrosion behavior of the obtained magnesium were investigated by means of a 3%NaCl salt-water immersion test, a 5%NaCl salt-water spray test and an electrochemical method. The corrosion resistance of magnesium is unaffected by specimens containing 104 ppm, or less, of Fe in both the 3%NaCl salt-water immersion and the 5%NaCl salt-water spray environment. However, it is deteriorated by specimens containing more than 16 ppm of Ni in the 3%NaCl salt-water immersion and specimens containing more than 23 ppm of Ni in the 5%NaCl salt-water spray environment. While it is unaffected by specimens containing 1660 ppm, or less, of Cu in the 3%NaCl salt-water and specimens containing 250 ppm, or less, of Cu in the 5%NaCl salt-water spray environment. The current density of the anodic part of polarization curve does not vary significantly with the amount of impurities. But the current density of the cathodic part increases as the amount of the impurities increases.