In-situ repair of marine coatings by a Fe3O4 nanoparticle-modified epoxy resin under seawater

[Display omitted] •An in-situ repair strategy for organic coatings under seawater was proposed.•The OMNPs exhibit super target-driving and competitive-wetting ability.•The impermeability and adhesion strength enhanced after being repaired. The in-situ repair of organic anticorrosive coatings under seawater is an ideal method to extend their service life once the coatings suffer from unexpected damage. However, the attachment and solidification of the repairing organic binder on the defects under seawater are two big challenging issues, which may lead to serious delamination and bad impermeability in the repaired coatings. Inspired by the attachment of barnacle larvae, lipophilic magnetic Fe3O4 nanoparticles were prepared via a co-precipitation method and then modified with oleic acid in this study. They were mixed with epoxy binder to squeeze away the seawater between the epoxy binder and substrate metals with the aid of magnetic force. The experimental results proved that the Fe3O4 nanoparticles had target-driving and competitive-wetting functions, which could effectively prevent the formation of penetrating micro-channels and enhance the adhesion strength of the organic binder to substrate metals. The new method may provide a repeatable and straightforward route for the in-situ repair of organic anti-corrosion coating under seawater.