Effect of surface area on corrosion properties of magnesium for biomaterials

This study examined the effect of the surface area on the corrosion properties of magnesium through in vivo (weight loss test) and in vitro (electrochemical and weight loss tests in Hank's solution) tests. The corrosion rate was reduced as the surface area increased. Surface analysis showed that the precipitation of calcium phosphate increased with increasing surface area. Moreover, the pH level around the specimen increased with increasing surface area. This increase of pH can accelerate the precipitation of calcium phosphate on the surface. However, different mechanism of calcium phosphate precipitation was found for in vivo and vitro test environment. In vitro environment showed an increase of calcium phosphate due to the continuous increase in pH, whereas in vivo environment showed increase of calcium phosphate to maintain homeostasis and reduced the level of pH in physiological system. Consequently, the increase in magnesium surface area leads to increase the precipitation of calcium phosphate as a more stable rust layer which ultimately increases the corrosion resistance of magnesium.