Synthesis of mint leaf extract and mint-leaf-based NiO nanoparticles, coating of extract layers without and with NiO nanoparticles on copper through drop-casting, and their analysis for the corrosion prevention in saline water

Abstract

Copper (Cu) loses its useful properties in some environments due to corrosion. This work proposes chloroform extract of mint leaves (CEML) as a coating material for lowering Cu loss in 0.5 M NaCl. The CEML has been synthesized using a simple extraction process and examined through UV-Vis and FTIR spectroscopy. NiO nanoparticles (NPs) are synthesized using water extract of mint leaves (AEML) and studied using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) patterns. The investigation suggests that mint-leaf-modified NiO NPs have been formed. The CEML is drop-cast on Cu in layers (1–3 layers) without and with different amounts of NPs (5–20 mg). The corrosion prevention potential of CEML coating on Cu without and with NiO NPs has been examined using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and Tafel polarization curves (TPC). The maximum prevention efficiencies of 88% and 97% have been achieved using two layers of CEML coating and one layer of CEML with 15 mg NiO NPs. The surface conditions of the bare and coated Cu have been recorded using FESEM and atomic force microscopy (AFM), which reveal that the coated Cu (CEML and CEML + NiO) appears to be protected. The corrosion products have been analyzed using EDX, which indicates the presence of oxides, chlorides, and hydroxides of Cu. The hydrophobicity of the bare and coated Cu has been determined from water contact angle (WCA) measurements. A corrosion prevention mechanism is also proposed based on the results achieved.