2020 Volume 61 Issue 9 Pages 1798-1804
The effects of Al concentration and Zn addition on the corrosion resistance of Mg–Al–(Zn)–Ca-based magnesium alloy rolled sheets were investigated. AXM (Mg–Al–Ca) alloys containing 1 mass% Ca and AZX (Mg–Al–Zn–Ca) alloys containing 1 mass% Ca plus 1 mass% Zn with the Al concentration adjusted to 6, 7, 8, 9, and 11 mass% were prepared. The corrosion behaviors of the alloys in a 5 mass% NaCl solution were evaluated by weight loss and the penetration depth. Electrochemical methods based on corrosion potential measurements and impedance spectroscopy was applied to monitor the corrosion behavior. The hydroxide film formed on the alloy surface was characterized by GDOES and SEM/EDS. The AXM alloy with an Al content of approximately 8 mass% exhibited minimum corrosion rate, whereas the AZX alloy showed the opposite result in the same concentration range of Al. This phenomenon was analyzed in terms of the Al concentration in the matrix (α-phase), which was reduced by the precipitation of Mg17Al12 (β-phase) and the presence of Zn. The tendency of localized corrosion in high Al-containing AZX alloys was pointed out.
This Paper was Originally Published in Japanese in J. JILM 70 (2020) 56–62. The caption of Fig. 3 is slightly modified.
