Superhydrophobic Coating Based on Porous Aluminum Oxide Modified by Polydimethylsiloxane (PDMS)

Abstract

The aim of this study was to obtain a superhydrophobic coating by modifying anodized aluminum using polydimethylsiloxane (PDMS). In order to obtain a superhydrophobic coating on an aluminum substrate, a multistage treatment was implemented. Specimens of aluminum were treated by abrasive blasting, anodization in sulfuric acid, impregnation by PDMS, rinsing in toluene to remove excess of PDMS, and curing. A rough surface with an additional low free energy layer on it resulted in a superhydrophobic effect. The coating obtained has an average contact angle of 159°. The specimens were tested in terms of durability in natural conditions. Additionally, anti-icing and anti-fouling properties were evaluated. The coating was compared with anodized aluminum obtained by a basic process.

The effect of time and heat exposure on the wettability and glossiness of CAA and FPL coatings for aluminum substrates

“…The presence of bird's nest structures with tiny beehive cavities and the formation of micro and nanoscaled structures have enhanced the wettability, resulting in a measured contact angle of 15 degrees. This finding is consistent with other sources that confirm anodized coatings naturally exhibit excellent wettability [25] The critical temperature range for anodized coatings is 70 to 80 °C. The oxide layer cracks due to differences in thermal expansion coefficient between the oxide layer and the aluminum sublayer at this temperature range [28] (figure 6).…”

“…Anodized and FPL coatings have demonstrated a notable enhancement in wettability due to nanometer and micrometer roughness. This finding was reported by Olkowicz et al [25].…”

Durability and Additional Properties of Anodized Aluminum-Based Coatings with Different Wettability under Natural Conditions

“…The small contact area between the solid and the water impedes heat transfer and thus delays ice formation; therefore, some superhydrophobic surfaces may also have good anti-icing properties [ 6 , 7 ]. In addition, superhydrophobic surfaces are used as antifouling and antibacterial surfaces [ 7 , 8 , 9 ], but not all superhydrophobic surfaces have these additional properties.…”

“…One of the popular methods for aluminum surface protection is the anodization process. The anodization process can be carried out in sulfuric, phosphoric, oxalic, chromic and tartaric acids, among others [ 9 , 16 , 17 , 18 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. However, in industrial practice, sulfuric acid is most often used.…”

“…Originally, in industrial practice, this procedure was aimed only at improving the tribological properties of anodized elements. Currently, this idea is increasingly used in the production of hydrophobic and superhydrophobic coatings [ 9 , 16 , 17 , 18 , 19 , 24 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 38 , 39 , 40 , 41 ]. Researchers often try to obtain a porous structure by modifying the anodization process and using the additional etching of the coating before impregnation [ 24 , 29 , 30 , 35 ].…”