Temporary Anti-Corrosive Double Layer on Zinc Substrate Based on Chitosan Hydrogel and Epoxy Resin

Abstract

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.