Superhydrophobic and self-healing dual-function coatings based on mercaptabenzimidazole inhibitor-loaded magnesium silicate nanotubes for corrosion protection of AZ31B magnesium alloys

In this work, clinochrysotile-like magnesium silicate nanotubes (MS-TNs) were fabricated by a hydrothermal method and then modified with dodecyltrimethoxysilane (DTMS) for the first time to act as a superhydrophobic material (MS-TNs/DTMS), whilst the MS-TNs was used as a nanocontainer to load a corrosion inhibitor 2-mercaptabenzimidazole (2-MBI). Taking the advantage of epoxy resin as a coating matrix, the AZ31B Mg alloy substrate was coated successfully by MS-TNs(2-MBI) as the first layer (for self-healing anti-corrosion) and superhydrophobic MS-TNs/DTMS as the second layer (for superhydrophobicity and anti-corrosion). The wettability, functionality and physicochemical stability of the superhydrophobic surface as well as the anti-corrosion performances of the dual-function coatings were systematically investigated by characterization, testing and electrochemical measurements. The as-prepared dual function coating with water contact angle at about 155° and sliding angle at circa 5° not only showed robust mechanical stability and chemical durability, but also exhibited substantial improvement of anti-corrosion property for protection of AZ31B Mg in a long run. The corrosion current density decreased from 8.33 × 10⁻⁴ A·cm⁻² of bare Mg to 8.12 × 10⁻⁸ A·cm⁻² of the coated sample. Furthermore, MS-TNs/DTMS was applicable to various kinds of substrates (e.g., copper mesh, sponge, glass slide, cloth, A4 typing paper) and showed an excellent water repellency, demonstrating its potential usage in fabrication of superhydrophobic surface as a low-cost and environmentally-benign material.