Corrosion resistance of zinc–curcumin metal complex coating on copper in 3.5% NaCl medium

Purpose For the purpose of preventing corrosion in metals and alloys, coating techniques are given priority. The prevention of copper corrosion in NaCl solutions by various inhibitor compounds using the spin coating process has recently undergone substantial research. The development of eco-friendly corrosion inhibitors is crucial to replacing toxic conventional coatings. This study introduces a novel zinc–curcumin (Zn-CU) complex coating for enhancing copper corrosion resistance. The synergistic effect of zinc ions and curcumin’s antioxidant properties provides a sustainable, nontoxic protective layer. This research bridges the gap in green corrosion inhibitors by proposing a biodegradable, metal–organic hybrid coating with industrial potential for marine and electronic applications. The purpose of this study is to synthesize Zinc -Curcumin metal complex and to evaluate its corrosion resistance characteristics. Design/methodology/approach In a solution of 3.5% NaCl for three days, a Zn-CU metal complex was produced, and its resistance to copper corrosion was examined. A Zn-CU metal complex was prepared and its corrosion resistance towards copper corrosion in 3.5% NaCl solution for three days was studied. The corrosion resistance property of the synthesized compound was examined by potentiodynamic polarization, SEM and EDX. Metal complex coating on copper substrate was performed by spin coating technique using a nontoxic binder polyvinylpyrrolidone (PVP). Findings Experimental investigations showed that Zn–CU/PVP reduces copper corrosion and attains 85% inhibition efficiency. Utilizing organic inhibitor coatings is one contemporary method for defending metals against corrosion caused by acids, bases or neutrals. They serve as a barrier or protective layer depending on the construction either as an insoluble chelate barrier created by chemisorption or produced by physisorption in the metal/electrolyte interphase. The morphology (shape, branching or conformation), aromaticity and conjugation, bonding strength to the metal substrate, the presence of heteroatomic nitrogen, oxygen and/or sulphur and the type and number of bonding atoms or groups are some of the factors that affect an organic molecule’s ability to inhibit metal corrosion. Research limitations/implications Synthesis of less toxic green anticorrosive coatings by incorporating plant and natural extracts are not only eco-friendly but also provide excellent corrosion prevention. This work mainly focussed on the synthesize of an eco-friendly metal complex of zinc by incorporating curcumin (Zn-CU). The synthesized compound was coated on copper surface using a binder PVP by spin coating method. Corrosion inhibition efficiency of Zn-CU increased with the concentration of metal complex. The corrosion resistance was up to 85% with 300 mg/L−1 Zn-CU/PVP at 30°C. The corrosion resistance property of Zn-CU metal complex in corrosive environment of 3.5% NaCl for copper has been tested by polarization analysis, SEM and EDX. Electrochemical tests confirmed that Zn-CU complex showed better corrosion inhibition property. SEM supported by EDX confirmed the stability and elemental composition of coating on the copper surface. Practical implications The practical implications include: development of a green chemistry approach in corrosion resistance; showcase of ways that metal protection can be augmented by bioactive compounds such as curcumin; and provision of alternatives to toxic corrosion inhibitors. Social implications Zinc and its compounds are widely used for corrosion protection due to their ability to act as sacrificial anodes. Zinc-based coatings provide effective corrosion resistance by forming passive layers that inhibit metal oxidation. Recent studies have explored the potential of zinc–organic complexes in corrosion inhibition, but their full potential remains under investigation. Recent research has focused on the synergistic effect of combining curcumin with zinc to enhance corrosion resistance (Rajendran et al., 2025; Xue et al., 2023). Zn-CU complexes offer multiple advantages, including improved stability, better adhesion to the metal surface and enhanced antioxidant properties (Mourya et al., 2019; Ashwini et al., 2023). However, there is limited literature on their application as protective coatings for copper surfaces, presenting a research gap that this study aims to address. The goal of this work is to investigate the ability of a Zn-CU complex coating to inhibit corrosion on copper in 3.5% NaCl solution using potentiodynamic polarisation and SEM/EDX. Originality/value This coating provides excellent corrosion inhibition owing to the synergistic effects of Zn²+ ions, released from sacrificial anode and curcumin, which facilitates the protection of metals from corrosion. Zinc gives sacrificial protection that minimizes metal oxidation, while curcumin is the organic inhibitor that results in a stable protective layer that hinders the initiation of corrosion. Curcumin can reduce the oxidative stress on metal surfaces due to its antioxidant properties and also inhibit the growth of bacteria that can cause corrosion. In contrast to conventional chemical inhibitors (e.g. chromates), curcumin is biodegradable and nontoxic; thus, it is considered as a sustainable approach.