Fabrication of durable and regenerable superhydrophobic coatings with excellent self-cleaning and anti-fogging properties for aluminium surfaces

Abstract

In this paper, superhydrophobic coatings on aluminium surfaces were prepared by chemical etching process using sodium hydroxide and lauric acid. The surface morphology analysis shows the presence of a rough microstuctures on the treated surfaces and the contact angle measurements confirm the superhydrophobic nature with high static contact angle of 170° and low sliding angle of 5°. Additionally, the effect of etchant concentration and etching time on wettability and morphology is also studied and observed that the contact angle increases with etchant concentration as well as with etching time as roughness enhances. Coating maintains its superhydrophobicity after undergoing 15 cycles of adhesive tape peeling test and under a stream of water jet. Coating remains unaffected on 90° and 180° bending, and repeated folding and de-folding. In addition to the above, coating can withstand after annealing temperature range from 40 to 170 °C and also stable under prolonged UV irradiation. Coating also maintains its superhydrophobicity upto one and four days when immersed in 5% acetic acid and 3% sodium chloride solution, respectively. Although, coating surface is fully damaged after annealing at 300 °C and superhydrophobicility turns into superhydrophilicity, but it regains by simply immersing again in lauric acid solution. Further, coating exhibits the excellent self-cleaning and anti-fogging properties. The aforesaid stable superhydrophobic aluminium surfaces have potential industrial applications.