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Natural and waste materials could be a successful and economical strategy for saving metals from corrosion because they could easily exchange electrons with the metals through their biomolecules. This work reported the use of waste sponge gourd peels (SGP) for the suppression of mild steel (MS) loss after dipping in 0.5 M NaCl. The water and ethanolic extracts of sponge gourd peels (SGPAE and SGPEE) had been prepared and characterized by Fourier transform infrared spectroscopy (FTIR). Both extracts were found to be loaded with biomolecules. SGPAE was used as an inhibitor, and SGPEE was utilized as a coating. Different concentrations (50–300 mg L−1) of SGPAE were added to 0.5 M NaCl, and SGPEE layers (1–5) were deposited on MS via drop casting and then exposed to salty water. The corrosion testing had been performed by open circuit potential (OCP) monitoring, Tafel polarization curves (TC), electrochemical impedance spectroscopy (EIS), field ion emission scanning electron microscopy (FESEM), energy dispersive X-ray spectra (EDX), and atomic force microscopy (AFM). The testing had shown that both extracts were effective against MS corrosion. SGPAE had shown maximum inhibition at 200 mg L−1 (75%), and SGPEE had shown maximum protection of 83% for 4 layers. The cause of MS protection by SGP was claimed to be the coverage of MS by the adsorbed molecules (SGPAE) or thin barrier layers of molecules (SGPEE). The reason for protection was also explained through an illustration. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]