Zein-oleic acid as a green, transparent and effective biofilm for copper corrosion protection

Purpose This study aims to introduce the efficacy of zein-oleic acid (ZO) nanobiocomposite coatings as an environmentally friendly inhibitor of corrosion on copper substrates in a 3.5% NaCl environment. Design/methodology/approach The composition of proposed biopolymer-based coating as a copper corrosion inhibitor was optimized using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) techniques. Findings Polarization studies show that the inhibitor decreases the corrosion current density by mixed mode mechanism. An equivalent circuit model was used to analyze the EIS data of electrode /electrolyte interface. SEM images reveal the presence of an adsorbed protective film of green inhibitor. Supplementing these observations, FTIR spectroscopy exhibits chemical behavior and integrity of a protective film, corroborating ZO’s role in providing a barrier to corrosive species. The biopolymer’s stability and synergistic interaction with the hydrophobicity of fatty acids position ZO as an environmentally friendly alternative for corrosion inhibition in chloride environments. The thin-film coating prepared from casting solution 0.5% w/v-0.03% oleic acid and 1.5% w/v-0.03% oleic acid show high inhibition efficiencies (η) of 92.31% and 92.64%, respectively, after 2 h of immersion in saltwater. Practical implications Considering the wide applications of copper in various industrial technologies, introducing an effective corrosion protector can significantly reduce damage caused by metal corrosion. The ZO nanobiocomposite film on copper can be used as a green and inexpensive corrosion protective layer on copper in humid and dry media. Originality/value The outstanding advantages of the ZO nanobiocomposite include ease of preparation, good adhesion to the copper surface, acceptable stability, transparency and high efficiency in inhibiting copper corrosion.