Preparation of gahnite (ZnAl2O4) superhydrophobic coating on aluminum alloy with self-healing and high stability properties

Gahnite (ZnAl2O4) is widely used in different fields including optics and catalysis, but is rarely used as the superhydrophobic material. Thermal decomposition of layered double hydroxide (LDH) materials is a way to prepare gahnite materials. In this paper, a Zn-Al LDH coating in-situ grown on aluminum alloy 6061 was used as the precursor, and a gahnite superhydrophobic coating was fabricated by calcination and stearic acid modification. The effects of calcination temperature and calcination time on the wettability and microstructure of the gahnite coating were investigated. It showed that a micro-sheet structure attached by nanoneedle was constructed after calcining the Zn-Al LDH coating at 500 degrees C for 2 h. After modification, the stearic acid molecules were stored on the coating due to the chemical bonding and adsorption, obtaining a superhydrophobic surface with the average contact angle of 158.8 degrees and the sliding angle less than 2 degrees. Compared with the Zn-Al LDH superhydrophobic coating without calcination, the stability in mechanical damage, high-temperature environment, and different chemical solutions of gahnite superhydrophobic coating was obviously improved. Furthermore, after chemical damage or contamination, the superhydrophobic property of the gahnite coating could be self-healing by external high-temperature stimulati.