preparation of novel mof-based thin film coating for corrosion protection of mild steel; surface/electrochemical studies

Conventional conversion coatings (ccs) such as chromate (cr) and phosphate (ph) have been applied for steel substrate modification in various industries for achieving excellent corrosion resistance and high adhesion properties of the subsequent organic coating. however, apart from their good properties, they provide toxic waste materials that cause serious risks to the environment and human health. to avoid these, the eco-friendly conversion coatings, i.e. cerium-based cc, has been used for this purpose. due to the porous nature of the ce-based ccs, they could not provide good corrosion resistance. so, improving their corrosion protection properties by adding additives or applying post-treatment is one of the recent studies topics. in this study for the first time, the thin metal-organic framework (mof) film was applied to the ce-treated sample. for this purpose, at first, a cerium conversion layer was deposited on the metal plates (st-12). then the coated plates were placed in the bath containing metal node and organic ligand to form a thin film based on zif-8 crystals. in this regard, at first, steel plates were thoroughly polished and pretreated by sanding. then, the cerium conversion coating solution was sprayed on the heated plates. next, the plates were immersed in a solution of zinc chloride, 2-methyl imidazole, and sodium formate in methanol and heated in an autoclave at 85°c for 24 h. finally, the plates were thoroughly washed with methanol and stored in a suitable place after drying. according to the results of ftir and xrd analyses, the successful formation of zif-8 based thin film on the plates coated with cerium cc was proved. also, the electrochemical impedance spectroscopy (eis) test showed that the formation of a thin film coating based on a metal-organic framework led to a significant increase in corrosion resistance.

Preparation of Novel MOF-based Thin Film Coating for Corrosion Protection of Mild Steel; Surface/Electrochemical studies

Conventional conversion coatings (CCs) such as chromate (Cr) and phosphate (Ph) have been applied for steel substrate modification in various industries for achieving excellent corrosion resistance and high adhesion properties of the subsequent organic coating. However, apart from their good properties, they provide toxic waste materials that cause serious risks to the environment and human health. To avoid these, the eco-friendly conversion coatings, i.e. cerium-based CC, has been used for this purpose. Due to the porous nature of the Ce-based CCs, they could not provide good corrosion resistance. So, improving their corrosion protection properties by adding additives or applying post-treatment is one of the recent studies topics. In this study for the first time, the thin metal-organic framework (MOF) film was applied to the Ce-treated sample. For this purpose, at first, a cerium conversion layer was deposited on the metal plates (st-12). Then the coated plates were placed in the bath containing metal node and organic ligand to form a thin film based on ZIF-8 crystals. In this regard, at first, steel plates were thoroughly polished and pretreated by sanding. Then, the cerium conversion coating solution was sprayed on the heated plates. Next, the plates were immersed in a solution of zinc chloride, 2-methyl imidazole, and sodium formate in methanol and heated in an autoclave at 85°C for 24 h. Finally, the plates were thoroughly washed with methanol and stored in a suitable place after drying. According to the results of FTIR and XRD analyses, the successful formation of ZIF-8 based thin film on the plates coated with cerium CC was proved. Also, the electrochemical impedance spectroscopy (EIS) test showed that the formation of a thin film coating based on a metal-organic framework led to a significant increase in corrosion resistance.