Preparation and Corrosion Resistance of Superhydrophobic Composite Coatings on Shot-Peened AA 7075-T6 Aluminum Alloy

Abstract

In order to further improve the corrosion resistance of 7075-T6 aluminum alloy after shot peening, corrosion-resistant superhydrophobic coatings (EP-HDTMS@SiO2) containing epoxy resin (EP), cetyltrimethoxysilane (HDTMS), and nano-silica (SiO2) were prepared by a simple spraying method on the surface of shot-peened AA 7075-T6 aluminum alloy. The effects of different EP/SiO2 mass ratios on the micro-morphology, surface wettability, and corrosion resistance of the superhydrophobic composite coatings were analyzed. Due to the combination of microstructure and the modification of low surface energy organics, the contact angle of EP-HDTMS@SiO2 coatings reached the superhydrophobic level (152.6°). The electrochemical tests showed that the corrosion current densities (Icorr) of the EP-HDTMS@SiO2 composite coatings were both significantly lower than those of the EP-HDTMS coatings and matrix aluminum alloys. The addition of SiO2 nanoparticles could improve the hydrophobicity and corrosion resistance of epoxy-based composite coatings. Due to the increase in surface roughness and epoxy resin, the shot-peened AA 7075-T6 alloy coating had high adhesion after the peel test. The prepared coatings also showed excellent corrosion resistance in the neutral salt spray test. This study provides a simple method for preparing stable superhydrophobic coatings on metal surfaces, which is expected to expand the application of 7075 aluminum alloy in harsh environments.