Effect of Beta vulgaris L. extracts as an additive on the electrodeposition of zinc on mild steel in chloride solution: coating characterization and corrosion behavior in seawater

Abstract

Mild steel (MS), characterized by its low carbon content (0.05–0.25 %), is widely used in various industries but is vulnerable to corrosion, which limits its durability. Zinc electroplating, a well-established technique to protect MS, involves the deposition of a thin layer of zinc onto a metal substrate. This forms a corrosion-resistant zinc coating. In this study, natural phenolic extracts from Beta vulgaris L., specifically methanolic (ME), dichloromethane (MDE), ethyl acetate (EAE), and n-butanol (BE) extracts, were analyzed via HPLC-DAD and utilized as eco-friendly additives in zinc electroplating baths composed of ZnCl₂, KCl, and H₃BO₄, to improve the quality and corrosion resistance of zinc coatings on MS. Incorporation of these extracts into the plating bath significantly improved the quality of zinc deposits. The enhanced brightness and refined surface morphology observed through scanning electron microscopy (SEM) and profilometry not only indicate the enhanced quality of the coatings but also suggest potential applications in industries where aesthetics and surface finish are important. Gravimetric corrosion tests and electrochemical evaluations, including potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS), demonstrated that zinc coatings formed in the presence of Beta vulgaris L. extracts exhibited remarkable corrosion resistance compared to conventional coatings. In addition, density functional theory (DFT)-based calculations were performed to investigate the adsorption behavior and chemical reactivity of the main phenolic compounds identified. Theoretical results revealed that ellagic acid exhibits the highest chemical activity, highlighting its key role in improving deposition efficiency and corrosion protection. This research underscores the potential of Beta vulgaris L. phenolic extracts as sustainable, natural additives for enhancing zinc electroplating processes. This offers a novel, environmentally friendly approach, addressing both performance enhancement and sustainability, and instilling hope for a more sustainable future in industrial plating processes.