Corrosion Behavior of Graphene Nanosheets Reinforced Magnesium Matrix Composites in Simulated Body Fluids

Magnesium (Mg) alloy is considered as a promising biodegradable implant material but restricted to rapid degradation. Here, the new strategies based on thixomolding process had been explored to utilize the outstanding anti-permeability of graphene nanosheets (GNPs) while inhibit its galvanic corrosion with the matrix, so as to improve the corrosion resistance of composites. The agglomerate of GNPs with 0.9 wt% content is the main reason for the deterioration of corrosion performance due to the formation of micro-galvanic corrosion. The grain refinement of composites with 0.6 wt% content had positive effects on the better corrosion resistance. After process adjusting, the unique distributions of GNPs along grain boundaries play a vital role in improving the corrosion resistance. It can be ascribed to the following mechanisms: (I) The barriers can be established between the Mg matrix and corrosive medium, hence blocking the charge transfer at the interface; (II) The GNPs can effectively promote apatite deposition on the Mg matrix, leading to form dense apatite layers and prevent the further invasion of SBF; (III) The GNPs acting as reinforcements exists in the corrosion layer and apatite layer, impede the apatite layer falling off from the Mg matrix. These findings broaden the horizon for biomedical applications in Mg matrix composites to realize desired performances.