A novel high-efficient MOFs-based corrosion inhibitor for the reinforcing steel in cement extract

Metal-organic frameworks (MOFs) can be potentially applied as corrosion inhibitors for reinforced concrete due to their supramolecular structure. In this study, zeolitic imidazolate framework (ZIF-8) was prepared by facile and eco-friendly solvent method. The inhibition effect of the prepared ZIF-8 corrosion inhibitor on the reinforcement in cement extract was investigated by electrochemical measurements (electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization (PD)) combined with surface analysis (field emission scanning electron microscope (FESEM) and Raman spectroscopy); the adsorption behavior of ZIF-8 corrosion inhibitor on the steel surface was analyzed by UV-vis spectrophotometer and atomic force microscope (AFM). The results indicated that ZIF-8 corrosion inhibitor with the diameter of about 75 nm was successfully synthesized. In chloride-containing cement extract, ZIF-8 corrosion inhibitor was efficiently adsorbed on the reinforcement surface and mainly reduced the anodic reaction rate by halting the dissolution of the reinforcement, thus significantly increasing the charge transfer resistance and polarization resistance of the reinforcement and exhibiting high inhibition efficiency (>95 %) during the initial 24 h. The pH drop caused by pitting propagation at the local corrosion sites resulted in the decomposition of ZIF-8 and Fe-N coordination bond formed between the released 2-MeIm ligands and reinforcement. As a result, the accumulation of corrosion products was pronounced prohibited, thus corrosion initiation of the reinforcement was significantly delayed and the inhibition efficiency was still maintained at 87.8 % after 168 h with ZIF-8 concentration of 0.04 wt%.