Synergistic effects of inorganic oxides on poly(3-amino-5-mercapto-1,2,4-triazole) electropolymerized films for the corrosion inhibition of Cu–Ni (90/10) alloys in an aqueous sodium chloride medium

Abstract

In this work, composite coatings were developed on Cu–Ni alloy substrates through the electrochemical polymerization of 3-amino-5-mercapto-1,2,4-triazole (3-AMTa), followed by the incorporation of inorganic oxides such as TiO₂, ZnO, CeO₂, and SiO₂ using a cyclic voltammetric deposition method. The corrosion protection behaviour of the resulting coatings was evaluated in a neutral medium using electrochemical impedance spectroscopy and Tafel polarization analysis. Structural features were characterized by Fourier-transform infrared spectroscopy and X-ray diffraction, while scanning electron microscopy, energy-dispersive X-ray spectroscopy and atomic force microscopy provided detailed insights into the surface morphology, elemental composition and topography of the prepared polymeric matrix, respectively. Electrochemical studies revealed that the incorporation of metal oxides into the poly-3-AMTa matrix significantly lowered the corrosion current density and improved the inhibition efficiency compared with the uncoated Cu–Ni alloy. The inhibition efficiency followed the sequence of TiO₂ (96.8%) > ZnO (93.2%) > CeO₂ (89.3%) > SiO₂ (80.6%) > poly-3-AMTa (73.2%), demonstrating the superior corrosion resistance imparted by TiO₂. AFM observations showed that the TiO₂-based composite coatings possessed the smoothest and most compact surface, while the addition of metal oxides generally enhanced the film uniformity, reduced the surface defects, and modified the surface roughness. Scanning electron microscopy images further confirmed the formation of dense, adherent, and defect-free coatings, particularly in the TiO₂-modified coatings. The X-ray photoelectron spectroscopy techniques demonstrated the elemental core-level spectra of C 1s, N 1s, S 2p, Ti 2p, Ni 2p and Cu 2p. This could be due to the back-donation of TiO₂, which binds to the poly-3-AMTa molecule. These results indicate that embedding metal oxides within the poly-3-AMTa framework markedly improved the barrier protection, surface integrity, and electrochemical stability of the Cu–Ni alloy coatings, with TiO₂ emerging as the most effective oxide additive for enhanced corrosion resistance in neutral and aggressive environments.