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Montmorillonite (MMT) clay mineral is widely used as filler for several organic coatings. Its activity is increased by exfoliation via chemical modification to produce nanomaterials. In the present work, the modification of MMT to form nanogel composites is proposed to increase the dispersion of MMT into epoxy matrices used to fill cracks and holes produced by the curing exotherms of epoxy resins. The dispersion of MMT in epoxy improved both the mechanical and anti-corrosion performance of epoxy coatings in aggressive marine environments. In this respect, the MMT surfaces were chemically modified with different types of 2-acrylamido-2-methyl propane sulfonic acid (AMPS) nanogels using a surfactant-free dispersion polymerization technique. The effect of the chemical structure, nanogel content and the interaction with MMT surfaces on the surface morphology, surface charges and dispersion in the epoxy matrix were investigated for use as nano-filler for epoxy coatings. The modified MMT nanogel epoxy composites showed excellent resistance to mechanical damage and salt spray resistance up to 1000 h. The interaction of MMT nanogel composites with the epoxy matrix and good response of AMPS nanogel to sea water improve their ability to act as self-healing materials for epoxy coatings for steel.

Superhydrophobic epoxy nanocomposites coatings with superior mechanical and adhesion strength are targeted to increase epoxy coating performance and to protect steel corrosion in aggressive environment. The present work prepared hydrophobic organic modified inorganic nanoparticles (NPs) based on magnetite, titanium dioxide and silver capped with epoxide oleic, linoleic and linolenic fatty acids. Their chemical structures, thermal stability, crystalline lattice structure, morphology and particles sizes distribution were determined using different tools. The curing exothermic reactions and thermal mechanical properties of the cured commercial epoxy with polyamine hardener were evaluated in the presence of the modified NPs to investigate their effect on the curing mechanism and crosslinking densities of the cured epoxy networks. The adhesion strength, abrasion resistance, seawater contact angles and seawater salt spray resistances of the cured epoxy coatings were evaluated on the steel surfaces. The obtained results confirm that the increasing weight contents of the modified NPs embedded into epoxy networks via chemical linking affect the adhesion, superhydrophobicity and anticorrosion performances of the cured epoxy coatings on the steel surfaces.

New epoxy resin hardeners were prepared from the reaction of p-nonylphenol and cardanol glycidylether with pentaethylenehexamine (PEHA) to produce hydrophobic polyamines. They were used as capping to produce superhydrophobic magnetite nanoparticles (Fe3O4 NPs). The chemical structures, thermal stability, morphologies, and particle sizes diameters were evaluated to confirm the hydrophobicity of dicardanoxy (DCHI) and dinonylphenoxy (HPHI) polyamines. The curing exothermic reaction of bisphenol A diglycidyl ether (DGEB) epoxy resin with DCHI, HPHI, or their Fe3O4 NPs was investigated by dynamic mechanical analyzer and differential scanning calorimetry. The cured epoxy networks crosslinking densities, storage modulus, and glass transition temperatures were determined and correlated to epoxy networks chemical compositions. DGEB/DCHI and DGEB/HPHI with their stoichiometric ratio embedded with their Fe3O4 NPs were applied on the rough steel surface to produce hydrophobic and superhydrophobic epoxy coatings. The wetting characteristics of the cured epoxy nanocomposites were evaluated from seawater contact angle (WCA) measurements to prove the formation of superhydrophobic coatings in the presence of DCHI-Fe3O4 NPs having WCA > 150°. The excellent adhesion, mechanical, and anti-corrosion performances using DGEB/DCHI and DGEB/HPHI epoxy nanocomposites were obtained on the steel surfaces in the presence of seawater corrosive environment.