The non-crystalline metal-organic framework for corrosion inhibitor behavior in sodium chloride solution

The metal-organic frameworks (MOFs), namely ZIF-62, have the ligand of imidazole and benzimidazole, which are effective corrosion inhibitors. In this context, ZIF-62 is an ideal candidate in marine corrosion protection. However, it is not reported till present. Here, the non-crystalline ZIF-62 (g-ZIF-62), a novel corrosion inhibitor carrier, is developed by melting the ZIF-62 crystal (c-ZIF-62) and its corrosion inhibition performance on AZ91 Mg alloy is investigated by electrochemical measurement. The results show that ZIF-62 could effectively inhibit the Mg alloy from corrosion. More significantly, g-ZIF-62 shows a better corrosion inhibition effect, and the corrosion inhibition efficiency (η) is up to 83.6%. The glassy grain boundaries of g-ZIF-62 disappear when melting the c-ZIF-62, which hinders the invasion of corrosive media, e.g·H2O molecules, Na+ and Cl−, to improve the stability in seawater. More importantly, the molar ratio of imidazole to benzimidazole is adjusted by the reaction time (Tm). Given the significant steric hindrance, the much content of benzimidazole in g-ZIF-62(48 h) have high viscosity under Tm, leading to the formation of a pyknotic glass for the corrosion inhibitors. Thus, this study not only highlights the potential of ZIF-62 as a corrosion inhibitor, but also provides fresh insights for the application of non-crystalline MOF in harsh seawater corrosion.