One very promising method of imparting additional functional properties to aluminium products is to modify the surface of an aluminium alloy by anodic oxidation and impregnation of a porous oxide layer, thereby obtaining superhydrophobic properties.
The methods presented in this study involved a few steps. First, the substrate material was subjected to abrasive blasting to obtain a rough surface. Samples mechanically prepared with three different grades of roughness were then anodically oxidised to produce a thick (≈20 µm) oxide coating with adsorption properties. The adsorption properties of the oxide coating were then used to saturate the pores with a 10% PTFE aqueous suspension, diluted from a 60% commercial solution. This process resulted in an oxide coating with a developed surface area, which gained superhydrophobic properties after impregnation in a PTFE suspension. Anti-icing properties were also tested, and accelerated ageing tests were carried out in a climate chamber. The results obtained were analysed in light of the correlations between wetting angles, freezing delays of water droplets and the surface roughness profiles of the substrates, as well as corrosion resistance. Corrosion resistance was evaluated using Electrochemical Impedance Spectroscopy (EIS).
The combination of abrasive blasting, anodic oxidation and PTFE impregnation treatments resulted in hydrophobic and superhydrophobic surface properties. The best results for delaying water droplet freezing were obtained for the smooth surface sample, which also revealed the best corrosion resistance. After cycles of testing in a climate chamber, the hydrophobic and superhydrophobic properties of the surface did not decrease and were also characterised by very high corrosion resistance compared to pure aluminium after the anodic oxidation process.
The best results for delaying water droplet freezing were obtained for the smooth surface sample, which also revealed the best corrosion resistance.