Superhydrophobic F-SiO2@PDMS composite coatings prepared by a two-step spraying method for the interface erosion mechanism and anti-corrosive applications

Herein, we designed and fabricated a superhydrophobic fluorinated silica (F-SiO2) @ Polydimethylsiloxane (PDMS) coatings with the great corrosion resistance via a two-step spraying strategy. The superhydrophobic F-SiO2@PDMS coatings displayed higher non-wettability with contact angle of 153.2° and sliding angle only being 3°, when the content of F-SiO2 nanoparticles was 0.88 wt%. The microstructures could entrap more air pockets to form an air-layer at the apparent solid-liquid interface. As a consequence, the F-SiO2@PDMS coatings exhibited the great ability to resist the corrosion effect, where the anti-corrosive mechanisms (or behaviors) were discussed through the two aspects of experimental investigations and molecular modeling. Electrochemical experimental results confirmed that the superhydrophobic F-SiO2@PDMS coatings possessed the excellent corrosion resistance with the corrosion potential Ecorr positively moving to −0.13 V and the corrosion current Icorr as low as 2.0 × 10−7 A cm−2. Also, the electrochemical impedance modulus reached the value of 1.8 × 105 Ω cm−2 and increased approximately 3 orders of magnitude comparing with the aluminum substrate. This was mainly due to the non-wetting regime caused by the trapped air pockets, which was also verified by the electrochemical equivalent circuit. Furthermore, the molecular dynamics simulation accurately revealed the diffusion mechanism of the corrosive medium to further support the discussion of anti-corrosive behavior of superhydrophobic coatings.