Superhydrophobicity induced by CO₂ plasma treatment of Magnesium

Poor corrosion resistance of light weight magnesium (Mg) is one of the major bottlenecks limiting broad application of Mg alloy for lightweight vehicle frame, aircraft component and bio-engineering implants application. Here we report a new protective coating approach by an atmospheric, room temperature CO₂ plasma (CO₂-AP) technique. The CO₂-AP treatment demonstrates the formation of Mg carbonate, superhydrophobic anticorrosion layer on bare Mg surface resulting in more than 10-fold reduction in the corrosion rate, compared to the untreated Mg specimens. Surface characterizations such as XPS, SEM, TEM-EDX indicate the CO₂-AP forms nanostructured MgO, MgCO₃, and carbon layers on the Mg surface. Because MgCO₃ and MgO are known as hydrophilic, it is likely that the hydrophobic carbon layer leads to superhydrophobicity. We test our hypothesis by performing molecular dynamic (MD) simulations based on force-field potentials that are well established in the field. In particular, we investigate the fundamental mechanisms of interaction between water nanodroplets and different substrates at a finite temperature. They provide insight into the understanding of superhydrophobicity at the atomistic level. Our results should be instrumental in the development of new superhydrophobic surfaces.