Inhibition effect of monofluorophosphate-loaded ZIF-8 metal-organic framework nano corrosion inhibitors in reinforced mortar

Abstract

Inhibition effect of traditional corrosion inhibitors is significantly reduced under harsh marine environment. Hence developing corrosion inhibitors with strong adsorption to satisfy efficient corrosion protection for reinforced concrete in harsh marine environment is urgent. By using multiple adsorption sites and abundant internal pores in metal organic frameworks (MOFs), a novel highly efficient monofluorophosphate-loaded zeolitic imidazolate framework (MFP@ZIF-8) nano corrosion inhibitors are prepared by in-situ synthesis method in this study. The influence of MFP@ZIF-8 nano corrosion inhibitors on corrosion performance of reinforced mortar was extensively investigated. The corrosion initiation time of the reinforcement embedded in mortar is dramatically prolonged in the presence of MFP@ZIF-8 nano corrosion inhibitors. After corrosion initiation, FePO₄ product layer forms and the contents of corrosion products with higher protective properties (FeOOH and Fe₂O₃) are also increased on the surface of the reinforcement embedded in mortar with MFP@ZIF-8 nano corrosion inhibitors. Meanwhile, the porosity and chloride concentration at the reinforcement/mortar interface is reduced by 10.7 % and 30.5 % in the presence of 0.8 wt% MFP@ZIF-8 nano corrosion inhibitors after 210 days immersion in 3.5 wt% NaCl solutions. As a result, the corrosion resistance of the embedded reinforcement is significantly enhanced by MFP@ZIF-8 nano corrosion inhibitors. Higher corrosion inhibition efficiency is related to larger dosage of MFP@ZIF-8 nano corrosion inhibitors. The inhibition efficiency is 87.8 % and 65.8 % in reinforced mortar in the presence of 0.8 wt% MFP@ZIF-8 nano corrosion inhibitors after 180 days and 210 days immersion.