Corrosion Resistance of Superhydrophobic Structure on Magnesium Alloy Surface Prepared by Hydrochloric Acid-Laser Composite Etching and SA Modification

A superhydrophobic structure was prepared on the surface of as-polished AZ91 magnesium alloy by hydrochloric acid-laser composite etching and stearic acid (SA) modification. The surface morphology, wetting properties and corrosion resistance of the superhydrophobic structure were studied. The results show that a rough structure composed of micron-sized pits and tightly and orderly arranged convex was formed on the magnesium alloy surface after the composite etching; after subsequent SA modification, a micro-nano-scaled composite rough structure was formed. After the composite etching and SA modification, the surface exhibited superhydrophobicity with good water-repellent adhesion resistance. Compared with those of the as-polished magnesium alloy, the free corrosion potential of the superhydrophobic magnesium alloy obtained by the composite etching and SA modification increased, and the free corrosion current density decreased, showing good corrosion resistance. After soaking in 3.5wt% NaCl solution for 24 h, the superhydrophobic surface showed no obvious corrosion traces.