Electrochemical synthesis and surface protection of polypyrrole-CeO₂ nanocomposite coatings on AA2024 alloy

A facile approach based on electrochemical polymerization was used to synthesize polypyrrole/CeO₂ (PPy/CeO₂) nanocomposite on an AA2024 alloy surface. CeO₂ nanoparticles (NPs) embedded in the PPy matrix were observed using FESEM micrographs with EDX analysis. IR and UV–vis spectroscopy were used to characterize the synthesized PPy/CeO₂ nanocomposite. The Raman spectra reflected the interactions between the π-conjugated structure of PPy and CeO₂ NPs. TGA thermograms revealed improved thermal stability of the synthesized nanocomposite and were used to determine the amount of nano ceria incorporated in the PPy matrix. The electrochemical corrosion behavior of the coated alloys in 0.6 M NaCl solution was examined through potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) measurements. From these electrochemical studies, a larger shift of E_corr in the positive direction with a high amount of CeO₂ in the nanocomposite was obtained, as well as a maximum corrosion protection efficiency of 99.64% by incorporating 3% of CeO₂ NPs in the PPy coatings. EIS studies also confirmed the enhanced corrosion protection behavior of PPy/CeO₂ coatings with higher R_ct, R_f and lower CPE_dl values compared to those of pure PPy coatings. The results showed that the PPy coatings with CeO₂ nanoparticles can be potential coating materials for the corrosion protection of AA2024 alloys substrates.