Electrochemical analysis of self-healing coatings loaded with ammonium molybdate inhibitor carried by cellulose nanofibers to modify corrosion resistance on damaged steel surfaces.

Corrosion resistance and self-healing capabilities of epoxy coatings that have been enhanced with cellulose nanofiber (CNF)-loaded ammonium molybdate (NH4)2MoO4 and applied to mild steel substrates were investigated in this work. Additive concentrations 1, 2.5, and 5 wt% were added to the coating system to investigate the electrochemical behavior and healing efficiency in a 3.5% NaCl environment at room temperature. Electrochemical measurements, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization, revealed that increasing additive concentration resulted in a significant improvement in corrosion resistance. The results showed a considerable decrease in corrosion current density and corrosion rate, as well as an increase in polarization resistance, with the 5% addition sample having the greatest value. Anodic and cathodic processes were both reduced by the inhibitor-modified coatings' mixed inhibitory behavior. The electrochemical results were validated by optical microscope analysis, which showed decreased corrosion damage and the development of a compact protective layer at scratched locations, especially in samples containing 2.5% and 5% additive. With the 5% addition system, the self-healing efficiency rose to 97.80% from 91.92% for the clean epoxy coating. The findings show that the CNF-molybdate system controls inhibitor release and creates a protective barrier in situ, greatly increasing corrosion resistance and durability in harsh settings, making it a good self-healing coating.