A study of the mechanical and chemical durability of Ultra-Ever Dry Superhydrophobic coating on low carbon steel surface

Both mechanical and chemical durability of superhydrophobic (SH) surfaces are very important properties for industrial applications. In this paper, the durability of the Ultra-Ever Dry, as a commercial SH product, sprayed onto low carbon steel has been systematically studied by sand paper abrasion, waterfall/jet test and immersion in solution of different pH values as well as salt spray test. The results show that the degeneration of superhydrophobicity of the coating during the abrasion was mainly due to the loss of both the top layer of micro-scale bumps and their nanoparticles (NPs). Waterfall/jet impact could also cause the loss of NPs on the micro-scale bumps of the coating, which corresponds with the change of wettability. Different chemical processes elicit complex effects on the SH Surface. The coating is able to maintain its superhydrophobicity in solutions of pH 1-12, whereas a solution of pH 14 causes both chemical change and loss of NPs, and as a result, the loss of the water-repellent property. The salt spray test shows that the pitting corrosion on the surface and the degeneration of superhydrophobicity are mainly induced by morphological and surface chemical changes such as the formation of new Fe-O nanostructures that presented as pit-etching on the coating surface. The results also confirm that surperhydrophobictity degeneration of the SH coating surface by salt spray can be easily recovered through treatment with fluoroalkylsilane (FAS-17). (C) 2016 Elsevier B.V. All rights reserved.