Biomimetic construction of green, fire-proof and super-hydrophobic multifunctionality-integrated coatings via one-step spraying method for steel structures

Recently, the exposed shortcomings of steel structures containing collapse at high temperature, severe corrosion phenomenon and susceptibility to pollution have gradually restricted their widespread applications in the significant fields of national economy. Aimed at overcoming these crucial problems, this paper was inspired by the superhydrophobic phenomenon on the surface of lotus leaves that the environmental and multifunction-integrated coatings with concave-convex scale-like micro-nanostructures were fabricated via one-step spraying method. Among the chemical composition of coatings, epoxy resin (EP) and silicone resin (SR) can act as the composite binders with good adhesion and hydrophobicity for attaching the fillers to the substrates. And the fillers composed of cyclodextrin-based flame retardant (MCDPM) and expandable graphite (EG) will exert the bidirectional action in fabricating the rough surface microstructure and enhancing the fire resistance of coatings. The results have revealed that as-prepared coatings exhibit low-adhesion super-hydrophobicity with the water contact angle (WCA) of 153.9° and the water sliding angle (WSA) of 8° that will induce a series of excellent performance in self-cleaning and corrosion resistance. In addition, good chemical stability and environmental durability have been simultaneously achieved for superhydrophobic coatings. Most of all, the exceptional fire protection ability of the designed coatings has been verified. Accompanied by the advanced formation of dense, continuous and high-yield char layers, the backside temperature of coated steel plate has been reduced to 269 °C during 1 h fire burning tests, which is far less than the critical collapse temperature of bare steel structure. Accordingly, compared to EP/SR coatings, the peak heat release rate (PHRR) and total heat release rate (THR) of the EP/SR-3 coatings are decreased by 68.8% and 96.6%, interpreting the intensified fire safety of coated steel structure. And the potential condensed flame-retardant mechanism has been further inferred and illustrated by systematically analyzing the combustion residue. Consequently, this paper has explored a straightforward route to address the issues of multiple defects for steel structures that extend the in-depth application in real-world fields.