Facile fabrication of graphene oxide and MOF-based superhydrophobic dual-layer coatings for enhanced corrosion protection on magnesium alloy

Corrosion is an inevitable and thorny problem when magnesium (Mg) alloys are used in marine environments. Superhydrophobic coatings have great potential for metal corrosion protection due to their superhydrophobicity and self-cleaning properties. However, the poor mechanical stability of the surface seriously hinders the practical application. Herein, a robust superhydrophobic graphene oxide (GO)/polypyrrole (PPy)-zeolitic imidazolate framework-8 (ZIF-8) dual-layer coating was prepared on the surface of magnesium (Mg) alloy by electrodeposition and spraying method, which was composed of a bottom GO layer and a upper superhydrophobic PPy/ZIF-8 layer. The GO layer extends the transmission path of corrosion ions and the superhydrophobic coating prevents the contact between the Mg alloy and the corrosive solution. In addition, the dual-layer superhydrophobic coating has excellent self-cleaning and mechanical properties. More importantly, the as-prepared coating can withstand 3.5 wt% NaCl solutions for 120 h and still maintain good corrosion resistance. Furthermore, the GO layer and the superhydrophobic layer have a synergistic effect, which significantly improves the corrosion resistance of Mg alloys. The facile method and superhydrophobic dual-layer coatings will have good application prospects on a variety of metal substrates.