Superhydrophobic coatings with enhanced adhesion for LA103Z alloy: Barrier-passivation synergy toward robust dual-stage corrosion protection

Developing durable superhydrophobic coatings is of great significance for enhancing the service performance of Mg-Li alloys. Herein, this study employs synergistic anodic oxidation-electrodeposition (AO-ED) technology to develop a superhydrophobic composite coating with hierarchical micro-nano structures on LA103Z alloy. Combining enhanced corrosion resistance, robust adhesion and self-cleaning functionality in one system, this coating significantly extends material lifespan. The synergistic interaction between the Mg(OH)₂ interlayer and the functional Ca[CH₃(CH₂)₁₂COO]₂ layer enhance the coating adhesion from Grade 2 to Grade 1. Electrochemical measurements reveal that the composite coating exhibits an ultralow corrosion current density (I_corr) of 2.80×10⁻⁸ A·cm⁻². Composite coating possesses a high charge transfer resistance (R_ct) of 2.47×10⁶ Ω·cm², representing a four-order-of-magnitude improvement over the bare substrate. The composite coating achieves long-term corrosion protection in 3.5 wt.% NaCl solution through a dynamic dual-stage mechanism. During the initial corrosion stage (0–7 days), the composite coating delays electrolyte penetration through the Cassie-Baxter superhydrophobic air cushion barrier effect (contact angle = 157.9°). In the subsequent protective phase (>7 days), long-term corrosion resistance is sustained by in-situ formation of a dense passivation film within the anodic layer, synergistically coupled with interfacial stability to maintain system impedance on the order of 10⁴ Ω·cm².