A novel approach towards controlled growth of metal-organic framework ZIF-8 thin film on steel with excellent corrosion protection

The control over the in-situ growth of metal-organic framework (MOF) thin films on a metal surface is still challenging. As an interesting subdivision of MOFs, the zeolite imidazole framework (ZIF) has been the research hotspot in various research areas, from separation to sensing in the form of nanocrystals, thin films, and membranes. Continuous thin films of ZIF crystals need binding sites for desirable heterogeneous nucleation. This study proposed a novel and facile surface treatment at room temperature based on zinc-phosphate conversion coating to provide nucleation sites for the intergrown ZIF-8 crystals on mild steel as a corrosion protective layer. The successful growth of ZIF-8 crystals on the modified carbon steel was characterized using FT-IR, Raman, GIXRD, XPS, and FE-SEM tests. This thin layer led to a super protective barrier film for up to 10 days in a harsh corrosive environment of salt spray. On the other hand, EIS reported almost 100 kΩ.cm2 total resistance after 72 h immersion in 3.5% wt. NaCl solution which is a great achievement compared to conventional primer coatings. The total resistance of an epoxy coating with the proposed primer was improved by 135% when there was a deep mechanical scratch in the coating. The ZIF-8 thin film could significantly improve the epoxy coating's anti-corrosion ability. The good news is that this concept is transferable to other ZIF-based MOFs.