Multifunctional coatings on magnesium alloy: Integrating superhydrophobicity, anticorrosion, and energy harvesting

Magnesium (Mg) alloys have gained increasing attention in industrial applications due to their exceptional strength-to-weight ratio, yet their susceptibility to corrosion remains a critical limitation. While superhydrophobic coatings have shown promise in addressing this challenge, their single anticorrosion function cannot meet the diverse demands under complex service conditions. This study reports a dual-layer polytetrafluoroethylene (PTFE) multifunctional composite coating fabricated by spraying on anodized AZ91 Mg alloy. The anodized layer enhances the interfacial bonding strength, while the dual-layer PTFE structure achieves both sealing protection for the oxide layer and low surface energy modification. The coating exhibits outstanding superhydrophobicity with a static water contact angle of 162°, along with excellent corrosion resistance, reducing the corrosion current density of the substrate from 2.19 × 10⁻⁴ to 5.32 × 10⁻⁷ A/cm². Moreover, the coating is cleverly designed into a liquid-solid triboelectric nanogenerator (L-S TENG), generating a short-circuit current of 7.1 ± 0.4 μA and an open-circuit voltage of 40 V. These results demonstrate that the developed coating not only significantly enhances the corrosion resistance and superhydrophobicity of Mg alloys, but also achieve an eco-friendly raindrop energy harvesting system. The proposed approach establishes a new solution for designing multifunctional coatings on Mg alloys, which greatly enhances their practical applicability.