Epoxy (EP) coatings containing silica (SiO₂) and (3-Aminopropyl)triethoxysilane-modified silica (SiO₂-APTES) nanoparticles were prepared via the dip-coating technique on a zinc substrate. A detailed study was performed regarding their incorporation into the matrix, followed by the investigation of the newly obtained organic–inorganic hybrid coatings’ anti-corrosive properties. The two methods of embedding the nanoparticles were (I) modification of the silica nanoparticles with APTES followed by their introduction into the epoxy resin, and (II) functionalization of the silica nanoparticles in the epoxy gel before the addition of the hardener. It was observed that through the second method, the coating was homogeneous, with no sign of agglomerates. The nanoparticles were subjected to morpho-structural and physical–chemical analysis using Fourier-Transform Infrared Spectroscopy and Transmission Electron Microscopy, while the coatings were examined through Scanning Electron Microscopy and Energy-Dispersive X-Ray Spectroscopy, contact angle measurements and adhesion tests. The anti-corrosive performance of epoxy-coated zinc was analyzed using electrochemical impedance spectroscopy and polarization curves to investigate the impact of silanized SiO₂ nanoparticle incorporation. Based on long-term corrosion testing, the epoxy-SiO₂-APTES composite coatings showed a higher corrosion resistance than the undoped epoxy layer.

In practice, metal structures are frequently transported or stored before being used. Even in such circumstances, the corrosion process caused by environmental factors (moisture, salty air, etc.) can occur quite easily. To avoid this, metal surfaces can be protected with temporary coatings. The objective of this research was to develop coatings that exhibit effective protective characteristics while also allowing for easy removal, if required. Novel, chitosan/epoxy double layers were prepared on zinc by dip-coating to obtain temporary tailor-made and peelable-on-demand, anti-corrosive coatings. Chitosan hydrogel fulfills the role of a primer that acts as an intermediary between the zinc substrate and the epoxy film to obtain better adhesion and specialization. The resulting coatings were characterized using electrochemical impedance spectroscopy, contact angle measurements, Raman spectroscopy, and scanning electron microscopy. The impedance of the bare zinc was increased by three orders of magnitude when the protective coatings were applied, proving efficient anti-corrosive protection. The chitosan sublayer improved the adhesion of the protective epoxy coating. The structural integrity and absolute impedance of the protective layers were conserved in both basic and neutral environments. However, after fulfilling its lifespan, the chitosan/epoxy double-layered coating could be removed after treatment with a mild acid without damaging the substrate. This was because of the hydrophilic properties of the epoxy layer, as well as the tendency of chitosan to swell in acidic conditions.

The expired drug Detralex (90% diosmin and 10% hesperidin), known as an effective corrosion inhibitor, was adsorbed onto mesoporous silica and incorporated into an epoxy matrix to enhance the coating’s corrosion protection in a highly corrosive 3 wt% NaCl solution. It was found that this treatment, by improving adhesion, modifying the hydrophilic properties, and enabling inhibitor release, increased the coating’s resistance over time. Based on an SEM-EDX analysis, even after 24 h of immersion, the epoxy coating with mesoporous nanosilica adsorbed with diosmin and hesperidin retained the incorporated inhibitors. This resulted in a slight increase in the samples’ polarization resistance during longer exposure.