Preparation of cerium-based superhydrophobic and corrosion-resistant coatings on the surface of AZ91D magnesium alloy via hydrothermal etching

Magnesium alloys exhibit excellent machinability, making them widely applicable in manufacturing industries. However, their inherently poor corrosion resistance significantly limits their broader utilization. To overcome this challenge, a composite coating was successfully fabricated on a magnesium alloy substrate via a hydrothermal etching approach. The resulting coating demonstrated outstanding superhydrophobicity and anticorrosion performance, achieving a water contact angle of 162°. Cross-cut adhesion tests yielded a strong bonding rating of 4B, and scanning electron microscopy characterization confirmed that the coating possessed considerable thickness, enabling it to maintain hydrophobicity while effectively resisting external abrasion. The coating’s corrosion resistance was rigorously evaluated through electrochemical impedance spectroscopy potentiodynamic polarization and acid-immersion tests. The Nyquist plots and polarization curves collectively indicated a significant enhancement in anticorrosion properties: specifically, the corrosion current density decreased by three orders of magnitude, and impedance increased by two orders of magnitude compared with the uncoated magnesium alloy substrate. Remarkably, the coating retained a contact angle of above 150° even after extended immersion in acidic solutions, highlighting its excellent chemical stability. Moreover, the coating exhibited superior self-cleaning capabilities, with external contaminant particles effortlessly removed by water droplets without compromising the coating integrity. Consequently, this methodology offers a promising route for advancing magnesium alloy surface protection technologies, laying a solid foundation for their application in more complex and challenging operational environments.