Construction of superhydrophobic GO/Ca coating on AZ31 magnesium alloy for enhanced anti-corrosion performance

Abstract

The application of magnesium alloys has garnered increasing interests in transportation, electronics and biomedical engineering fields, and the fabrication of superhydrophobic coatings on the surface of magnesium alloys is considered as an effective means to improve the corrosion resistance. However, major technical barriers restricting its application lie in the long-term durability and mechanical properties of superhydrophobic coatings. Herein, a calcium myristate coating with graphene oxide (GO) is fabricated on AZ31 magnesium alloy by electrodeposition. The coating is constructed in a particularly simple and gentle way by the synergy of inorganic nanomaterials and organic acid salts. It was found that the deposition time significantly affected the morphology, thickness and wettability of the GO/Ca coating and further influenced the corrosion resistance and durability. The best corrosion resistance is obtained when the deposition time is 30 min. With 30 min deposition, the corrosion current density of the substrate was reduced by 3 orders to (2.38 ± 1.02)× 10−9 A cm−2, and the impedance modulus at the lowest frequency could reach 108 Ω cm2. And after 21 days of immersion, the impedance modulus at low frequency of GO/Ca-30 is still as high as 105. It could be attributed to the tortuous path and denser structure with introduction of GO. Besides this, the scratch test and adhesion strength describe that the GO/Ca coating presents a good adhesion to the substrate. Considering its satisfying corrosion resistance, long-term durability and high adhesion strength, it is expected that the as-prepared superhydrophobic coating on AZ31 alloy is promising for anti-corrosion application.