Abstract
The enhancement of both thermal and mechanical properties of epoxy materials using nanomaterials becomes a target in coating of the steel to protect it from aggressive environmental conditions for a long time, with reducing the cost. In this respect, the adhesion properties of the epoxy with the steel surfaces, and its proper superhyrophobicity to repel the seawater humidity, can be optimized via addition of green nanoparticles (NPs). In-situ modification of silver (Ag) and calcium carbonate (CaCO3) NPs with oleic acid (OA) was carried out during the formation of Ag−OA and CaCO3−OA, respectively. The epoxide oleic acid (EOA) was also used as capping for Ca−O3 NPs by in-situ method and epoxidation of Ag−OA NPs, too. The morphology, thermal stability, and the diameters of NPs, as well as their dispersion in organic solvent, were investigated. The effects of the prepared NPs on the exothermic curing of the epoxy resins in the presence of polyamines, flexibility or rigidity of epoxy coatings, wettability, and coatings durability in aggressive seawater environment were studied. The obtained results confirmed that the proper superhyrophobicity, coating adhesion, and thermal stability of the epoxy were improved after exposure to salt spray fog for 2000 h at 36 °C.
Highlights
Published: 21 January 2021Marine environments have harsh conditions that cause the corrosion of different metals and the failure of adhesion of the applied coatings due to higher humidity, temperature, biocides, and salts [1]
The presence of epoxide group on the surfaces of oleic acid (OA) rearranged the assembly from one layer to multiple capping layers, as occurred in both CaCO3 −OA and CaCO3 −epoxide oleic acid (EOA)
New nanocomposites of epoxy coating applied on the steel surfaces in the presence of hydrophobic CaCO3 −EOA and Ag−EOA NPs showed stable mechanical abrasion resistance and seawater salt spray resistance, which were improved by the high adhesion of epoxy resin and the layered structure of particles
Summary
Marine environments have harsh conditions that cause the corrosion of different metals and the failure of adhesion of the applied coatings due to higher humidity, temperature, biocides, and salts [1]. The amendment of NPs with reactive functional groups such as epoxide, amine, and aminoamide during the curing of epoxy leads to an increase in the dispersion, adhesion, mechanical, and thermal characteristics of epoxy coatings due to their chemical linking with epoxy networks [18,22,23,24]. In this respect, the present work aims to modify the surface hydrophobicity of both silver and calcium carbonate NPs by epoxide oleic acid (EOA) and oleic acid, using in-situ technique to control the shape, sizes, and self-assembly of hydrophobic coatings on their surfaces. The coating durability of the epoxy nanocomposite coatings on the steel surface in the presence of high humidity seawater fogs at 36 ◦ C was evaluated at different exposure time using a salt spray resistance test
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