RESUMO
The anticorrosion performance of silane-modified chitosan/epoxy primer coatings was evaluated using quantum chemical computations (QCC) and molecular dynamics simulation (MDS) techniques. The objective was to appraise the molecular/atomistic level performance of silane-modified chitosan/epoxy primer coating system on mild steel in saline water to be able to design robust anticorrosion epoxy nanocomposite primer coating for marine application. The QCC showed that quantum parameters for (3-aminopropyl) trimethoxy silane-modified chitosan nanocluster (AMCN) are optimum and therefore correspond to high corrosion protective capability. The adsorption energies (Eads) for AMCN/epoxy, tetraethoxysilane-modified chitosan/epoxy, chitosan-modified epoxy, and unmodified epoxy coatings were found to be - 3094.65, - 2,630.00, - 2,305.77, and - 1,189.33 kcal/mol, respectively. The high negative value of Eads indicates the coating molecules interacted and adsorbed strongly on the mild steel surface. Hence, AMCN/epoxy coating is potentially most corrosion-resistant than the others. Further, it is established that shorter bond length corresponds to higher bond strength and therefore indicates chemical interaction. Thus, the radial distribution function showed the bond lengths between atoms of the AMCN and mild steel surfaces were shorter than those of other molecules. Overall, AMCN/epoxy coating molecules possess good anticorrosion properties and therefore would perform well if deployed for service in saline environments.
RESUMO
The use of epoxy and polyurethane coatings as marine topcoats, have been influenced by their inherent high surface energy property which increases their affinity to water and microorganisms. Thus, their susceptibility to degradation is enhanced. Because of this defect, recently, nanostructured hydrophobic and superhydrophobic polysiloxane coatings are being preferred as topcoats. But the appropriate nanoparticle size and matrix:filler ratio which provide guide for the design of desired topcoats are scarcely available. In view of this, a series of hydrophobic and superhydrophobic coatings were prepared by sol-gel process based on perfluorodecyltrichlorosilane (FDTS), different nanoZnO particles and poly(dimethylsiloxane) (PDMS):nanoZnO ratios. The liquid repellency, surface morphology and roughness of the coatings were conducted by use of contact angle goniometer, field emission scanning electron microscopy and atomic force microscopy, respectively. Additionally, the electrochemical and salt spray corrosion tests were conducted. According to the results, modifications of the coatings showed that anticorrosion performance was considerably influenced by the surface properties which were dependent on nanoZnO size and PDMS:nanoZnO ratio. Remarkably, the optimum effect was observed on the superhydrophobic coating based on 30â¯nm ZnO and 1:1 ratio. This displayed highest anticorrosion performance, and is therefore recommended as a guide for the design of marine topcoats.
RESUMO
Perfluorodecyltrichlorosilane-based poly(dimethylsiloxane)-ZnO (FDTS-based PDMS-ZnO) nanocomposite coating with anti-corrosion and anti-fouling capabilities has been prepared using a one-step fabrication technique. XPS analysis and contact angle measurements showed the fluorine content to increase, while the hydrophobicity of the coatings decreased with addition of FDTS. XRD analysis revealed existence of ZnO nanoparticles of dimensions ranging from 11.45 to 93.01nm on the surface of coatings, with the mean particle size decreasing with FDTS addition, and was confirmed by SEM and TEM observations. Interestingly, the anti-corrosion performance and mechanical properties of the coatings increased remarkably on addition of FDTS. Indeed, the observed low adhesion strength, surface energies and the outstanding anti-corrosive properties imply that the obtained coating would be useful in anti-fouling applications.
