Release rate kinetics of corrosion inhibitor loaded halloysite nanotube-based anticorrosion coatings on magnesium alloy AZ91D

Halloysite nanotubes were used as nanocontainers to hold corrosion inhibitors such as Ce3+-Zr4+, 2-mercaptobenzothiazole and 8-hydroxyquinoline in their lumen. An acid assisted etching of the nanotubes was carried out with a view to increase the lumen diameter and thereby, increase the amount of loading of the corrosion inhibitor. The morphology of as-received and etched halloysite nanotubes was observed using TEM analysis. The loading of corrosion inhibitors was confirmed using SEM-EDS and BET analysis. Polymeric microcapsules were used as capping agents for the ends of the loaded HNTs following which, they were dispersed into a hybrid sol-gel silica matrix. Dip coating method was used to generate coatings on AZ91D substrates followed by heat treatment at 130 degrees C for 1 h. The release rate kinetics of corrosion inhibitors from as-received and etched nanotubes was investigated in buffer solutions of 3.5 wt% NaCl at different pH. The release mechanism of corrosion inhibitors from the HNT lumen was validated using various semi-empirical models. Coatings were also evaluated for their corrosion protection ability using electrochemical techniques after exposure to 3.5 wt% NaCl solution for 120 h. Coatings generated using Ce3+-Zr4+ loaded into as-received halloysite nanotubes have shown more effective corrosion protection when compared to other corrosion inhibitors after 120 h exposure to the corrosive medium. (C) 2020 Published by Elsevier B.V. on behalf of Chongqing University.

Automated summary

Halloysite nanotubes were used as nanocontainers to hold corrosion inhibitors, and acid assisted etching was carried out to increase the loading of the inhibitors. The release kinetics and mechanisms of the corrosion inhibitors were investigated, with Ce3+-Zr4+ loaded coatings showing more effective corrosion protection compared to other inhibitors. The study demonstrates the potential of utilizing halloysite nanotubes for improving corrosion resistance in metal coatings.