Which of these materials is the most anodic?

Which of these materials is the most anodic?

• A. Cadmium
• B. 7075-T6 aluminum alloy
• C. Magnesium
• D. Zinc

Answer: (C)

Anodic behavior follows the tendency to lose electrons in an electrolyte: the more negative the metal’s electrode potential, the more readily it oxidizes and acts as the anode. Among these materials, magnesium has the most negative reduction potential, so it will oxidize first in a galvanic couple and behave as the most anodic. In practice, aluminum alloys can form a protective oxide layer that reduces further corrosion, and zinc and cadmium have less negative potentials than magnesium, so they are less prone to act as the anodic partner in the same environment. Therefore, magnesium is the most anodic choice.

Anodic behavior follows the tendency to lose electrons in an electrolyte: the more negative the metal’s electrode potential, the more readily it oxidizes and acts as the anode. Among these materials, magnesium has the most negative reduction potential, so it will oxidize first in a galvanic couple and behave as the most anodic. In practice, aluminum alloys can form a protective oxide layer that reduces further corrosion, and zinc and cadmium have less negative potentials than magnesium, so they are less prone to act as the anodic partner in the same environment. Therefore, magnesium is the most anodic choice.