Achieving acid resistance of magnesium alloy by superhydrophobic surface modification

Developing acid-resistant magnesium alloys is challenging because of the high chemical reactivity of magnesium in acidic media. In this work, a bio-inspired strategy by taking advantage of the superhydrophobic effects on lotus leaves is described. Hydrothermal treatment and magnetron sputtering are combined to produce superhydrophobic surfaces on AZ80 magnesium alloys. The hydrothermal process produces a self-layered barrier composed of an inner compact layer and outer Mg-Al layered double hydroxide (LDH) microsheet-based layer. This process improves the corrosion resistance in saline solutions but is not as effective in H₂SO₄. After depositing a fluorocarbon polymer film on the microsheets using a polytetrafluoroethylene (PTFE) target by magnetron sputtering, a Cassie-state superhydrophobic surface with a water contact angle of 170° is obtained. The Cassie-state superhydrophobic surface exhibits dropwise water condensation and icing retardation behavior. Compared to the hydrothermal method alone, the combined process yields better corrosion protection in both H₂SO₄ and NaCl solution due to the reduced liquid-surface contact and air pockets trapped among the microstructures. The dual-process offers a promising means to mitigate corrosion of magnesium alloys in acidic media.