Fabrication of a pH-Sensitive Epoxy Nanocomposite Coating Based on a Zn-BTC Metal–Organic Framework Containing Benzotriazole as a Smart Corrosion Inhibitor

In this study, a pH-sensitive Epoxy/BTA@Zn-BTC smart anticorrosion nanocomposite coating was fabricated by the encapsulation of a benzotriazole (BTA) corrosion inhibitor in a Zn-BTC metal–organic framework (MOF). The corrosion process of the coating was investigated for different durations of storing the coating in a corrosive solution of 3.5 wt % NaCl using potentiodynamic polarization (Tafel) plots and electrochemical impedance spectroscopy. The synthesized BTA@Zn-BTC nanocapsules have a loading capacity of 16.5% for BTA. The BTA encapsulated in Zn-BTC MOF is released as the corrosion zone becomes acidic, and it serves as a corrosion inhibitor. The released BTA inhibitor proved to have an inhibition efficiency of 98.8% to protect aluminum against corrosion in the corrosive solution after 3 days. A possible mechanism has been presented for the formation of a protective film in this process. It is argued that in the active areas of corrosion on the metal surface the local pH decreases and the H+ ions produced in the corrosion reaction rapidly penetrate into the BTA@Zn-BTC nanocapsules, releasing the BTA inhibitor. Then, the released inhibitor forms a dense barrier in the corrosion area to decrease the corrosion rate. As found in this study, the durability of this smart coating is significantly prolonged in a 3.5 wt % NaCl solution.