Fe/Zn/Ce-doped O-carboxymethyl chitosan-graft-polyaniline copolymer nanocomposite for corrosion protection of construction steel in acidic environments

This study reports the fabrication and evaluation of an innovative anti-corrosive agent composed of ternary nanoparticles of metals like iron (Fe), zinc (Zn), and cerium (Ce) into a copolymer matrix of oxy-carboxymethylated chitosan-graft-polyaniline (O-CMCs-g-PANi) for corrosion inhibition of carbon steel in acidic conditions. Four nanostructures, FeNPs@O-CMCs-g-PANi, ZnNPs@O-CMCs-g-PANi, CeNPs@O-CMCs-g-PANi, and Fe/Zn/CeNPs@O-CMCs were prepared through the carboxymethylation of chitosan, followed by graft polymerization of polyaniline and subsequent incorporation of Fe, Zn, and Ce nanoparticles. Characterization of the prepared nanocomposites was conducted through Fourier transform infrared spectroscopy, scanning electron microscopy paired with energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, selected area electron diffraction, and Brunauer–Emmett–Teller methods, showing that there was effective functionalization of the polymer network and uniform distribution of the metallic nanoparticles. As the concentration of the inhibitors increased, the corrosion inhibition efficiency increased to achieve values of 88.1%, 93.1%, and 98.6% at 200 ppm for ZnNPs@O-CMCs-g-PANi, CeNPs@O-CMCs-g-PANi, and Fe/Zn/CeNPs@O-CMCs-g-PANi, respectively. The electrochemical studies revealed that the ternary nanocomposite had better anti-corrosion properties than the mono-metal and bimetal systems. This is because the synergistic effect of Fe, Zn, and Ce oxides leads to a higher specific surface area and adsorption capability. In addition, the interfacial stability is increased, which gives rise to the formation of a protective film layer on the steel surface. Furthermore, the calculated standard free energy of adsorption values were more negative than −40 kJ mol ⁻¹ , indicating that corrosion inhibition predominantly occurs through chemisorption. These findings demonstrate that Fe/Zn/CeNPs@O-CMCs-g-PANi is a highly efficient and sustainable nanocomposite inhibitor with excellent potential for protecting carbon steel in aggressive acidic environments.