Linking the microstructure of a heat-treated WE43 Mg alloy with its corrosion behavior

• Alloy microstructure affects the corrosion behavior of heat-treated WE43.
• Corrosion domes form on Zr-rich impurity particles by a microgalvanic effect.
• A porous bi-layered corrosion film is formed by inward oxidation and hydration.
• Fine scale precipitates interfere with the propagation of corrosion reactions.
• Aging treatment can decrease the corrosion rate of WE43 alloys.

The corrosion microstructure of a WE43 Mg alloy immersed in 3.5 wt% NaCl solution saturated with Mg(OH)2 was characterized across several length scales in order to understand the relationship between corrosion behavior and the alloy microstructure developed after solution treatment and aging. Hydrogen bubbles evolved and protruding Mg(OH)2 domes formed on Zr-rich impurity particles by a microgalvanic effect. The observed porous bi-layered corrosion film was explained by inward oxidation and hydration reactions. Aging treatment decreased the corrosion rate of the alloy via the interactions between the finely dispersed precipitates and the corrosion reactions.