Dendritic structure formation of magnesium alloys for the manipulation of corrosion properties: Part 2-corrosion

In pure magnesium and aluminum-containing magnesium alloys, the microstructure also plays a role in the corrosion properties. In Part 1, the grain sizes, secondary dendrite arm spacings (SDAS) and precipitates of b phase were determined by casting samples with 0, 3, 6, 9 and 12% aluminum (all compositions in mass percentage) at different cooling rates. These samples were tested for corrosion properties by immersion and salt spray tests. The modeling of the corrosion process enables establishing a mathematical link between the microstructure and corrosion properties of an alloy. The results show an increase in the corrosion rate with increasing aluminum contents and the cooling rate.

The precipitations at the grain boundaries have a relevant impact on corrosion properties of the magnesium-aluminum alloys. A random comparison using the salt spray test tends to confirm the results.