Preparation of Durable Superhydrophobic Coating and Its Anti-icing, Anti-corrosion, and Self-cleaning Properties

Aluminum alloys are widely used in ships and offshore platforms owing to their high fatigue strength, excellent corrosion resistance, welding performance and cold workability. Although the surface of the aluminum alloy usually forms an oxide film innatural environments, the film is thin and can easily be damaged during application, resulting in damaging the substrate. Therefore, preparing anti-icing, anti-corrosion and self-cleaning superhydrophobic coatings on aluminum alloy substrates is important for improving their performance and expanding their application fields. Superhydrophobic surfaces are with a water contact angle exceeding 150 degrees and a roll-off angle below 10 degrees. Inspired by superhydrophobic surfaces of nature, researchers have successfully prepared and developed various artificial superhydrophobic coatings that can be applied in various fields, such as self-cleaning, anti-corrosion, and anti-icing. To date, many methods for preparing superhydrophobic coatings with micro-nano structures and low-surface-energy, such as spraying and electrodeposition, have been proposed. However, currently prepared superhydrophobic coatings are highly susceptible to damage because their rough surface morphology is easily damaged by mechanical wear, weak adhesion to the substrate, and poor resistance to harsh conditions, which seriously affects their large-scale application. Therefore, improving the wear resistance of superhydrophobic coatings is an urgent issue. For the micro-nanocomposite structures on superhydrophobic surfaces, the single micron-scale structure protects fragile and functional nanoscale structures because of its ability to withstand more frictional loads than nanoscale structures. Epoxy is a thermosetting resin, and its highly cross-linked three-dimensional network structure endows it with excellent bonding and adhesion performance. The use of sturdy adhesives, such as epoxy resin, to improve the adhesion between the coating and substrate. Moreover, spraying modified micro-nanocomposite particles to create micro-nanostructures is an effective strategy for the large-scale preparation of wear-resistant superhydrophobic coatings. Therefore, in this study, a simple and cost-effective method to prepare a dual-scale durable superhydrophobic coating on an aluminum alloy substrate by one-step spraying of micro / nano mixed particles is proposed. First, an epoxy resin adhesive layer was applied to the surface of the aluminum alloy substrate, after it reached a semi-cured state, a mixed suspension of stearic acid-modified micro SiO2 and nano TiO2 particles was sprayed. After curing, the contact angle between the coating and water was similar to 155.4 degrees and the roll-off angle was similar to 3 degrees, indicating excellent superhydrophobicity. The prepared coating surface shows an obvious micro-nanostructures, also modified by low-energy substances, which indicates microstructure and composition conditions for constructing superhydrophobic surfaces. The prepared superhydrophobic coating exhibited strong adhesion on substrate, excellent wear resistance and durability, also with good superhydrophobicity under various tests, including 19 times of tape peeling, 20 cm of sandpaper wear, long-term exposure to ultraviolet light, and droplet testing at different pH. The prepared superhydrophobic coating significantly delayed the freezing time of water in extremely cold weather by approximately eight times that of the substrate. Simultaneously, the synergistic anti-corrosion effect of the epoxy resin and superhydrophobic property caused the prepared coating to exhibit excellent anti-corrosion performance in seawater. In addition, the prepared superhydrophobic coating shows excellent self-cleaning performance, and can be used for the photodegradation of pollutants and purification of water because of the photodegradation performance of TiO2 particles. This simple and environmentally friendly superhydrophobic coating is promised to apply in anti-icing, anti-corrosion and other aspects, andprovides a solution for improving the durability of traditional superhydrophobic surfaces.