Evaluation of Ph-Sensitive Nanocontainers Composed of Hierarchical ZnO Mesoporous Structures Loaded with the Mimosa Tenuiflora Extract for Applications in a Saline Solution

In this work, a new low-toxicity nanocontainer is proposed to functionalize an epoxy coating. The nanocontainer is made up of 1) a hierarchical mesoporous structure of ZnO, 2) the Mimosa tenuiflora [Mt] extract, and 3) a tannic acid-iron complex (Fe-TA). The performance of the modified coating with ZnO/[Mt]@Fe-TA nanocontainers sprayed on low-carbon steel in a saline solution of NaCl (3.5%) is evaluated. The characterization of the hierarchical mesoporous structure of ZnO includes the specific surface area and adsorption/desorption isotherms obtained by BET method. Likewise, the chemical composition of the extract of the [Mt] bark is determined by Fourier Transform Infrared Spectroscopy and 13 C Nuclear Magnetic Resonance. The nanocontainers are characterized by X-Ray Diffraction, Scanning Electronic Microscopy, Thermogravimetric Analysis, and Differential Scanning Calorimetry. The performance of the coating added with ZnO/[Mt]@Fe-TA nanocontainers is carried out by Electrochemical Impedance Spectroscopy (EIS). The results exhibit that although ionic permeability occurs in the coating, the ZnO/[Mt]@Fe-TA nanocontainers are responsible for the formation of an oxide layer that mitigates the degradation of the coating. In addition, the electrochemical parameters show oscillations throughout the entire exposure time, suggesting that ZnO/[Mt]@Fe-TA nanocontainers could be potential pigments for a self-healing coating.