Encapsulation of the corrosion inhibitor 8-hydroxyquinoline into ceria nanocontainers

Ceria nanocontainers were synthesized through a two-step process and then loaded with 8-hydroxyquinoline (8-HQ). The size of the containers was 110 nm as determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction analysis (XRD) showed that the ceria nanocontainers were of the cerianite crystalline phase. The presence of 8-HQ in the nanocontainers was confirmed with Fourier-transform infrared spectroscopy (FT-IR). The loading of the inhibitor in the nanocontainers was estimated with differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The loading amount of 8-HQ was 4.28% w/w. Based on the size of the nanocontainers and the assumption that they are not broken, we deduced that there were approximately 6.0 × 10⁵ molecules of 8-HQ per container. Furthermore, release of 8-HQ in a corrosive environment was studied by potentiodynamic measurements, showing that the inhibitor is released from the nanocontainers, suppressing the corrosion activities by a strong barrier effect. SEM and dynamic light scattering (DLS) measurements confirmed that the nanocontainers are not significantly agglomerated and maintain their shape after suspension in 0.5 M NaCl solution for more than 72 h.