Mechanically durable PAL-based superhydrophobic composite coatings with a sandwich structure for corrosion protection of aluminum alloys

Conventional superhydrophobic composite coatings fail to meet the service needs of aluminum alloys in harsh environments due to their inadequate bonding of hydrophobic particles in the topcoat and vulnerability to organic contamination. To address these challenges, a palygorskite-based superhydrophobic composite coating has been developed, inspired by nacre. The coating is composed of an epoxy resin primer and a polydimethylsiloxane (PDMS) strengthened layer with superhydrophobic palygorskite in between, forming a sandwich structure. The effect of PDMS concentration on the coating's wettability, surface morphology, and mechanical durability was thoroughly investigated. Results show that at 0.3 g/mL PDMS concentration, the final coating (ESPP) exhibits optimal abrasion resistance, withstanding an abrasion distance of 8000 cm on 600-grit sandpaper under a 100 g load. When immersed in 3.5 wt% NaCl solution for 44 days, the low-frequency impedance modulus (|Z| lf ) of the ESPP coating maintains as high as 8.34 × 10 6  Ω∙cm 2 . Even when contaminated with organic contaminants, the coating's corrosion current density is 4 orders of magnitude lower, while its |Z| lf is four orders of magnitude higher compared to that of the coating lacking the PDMS layer. This study is expected to offer new insights into the design of mechanically robust and oil-resistant superhydrophobic anti-corrosion coatings.