Oil Extracted from Spent Coffee Grounds as a Green Corrosion Inhibitor for Copper in a 3 wt% NaCl Solution

The aim of this research is to study the use of the spent coffee grounds (SCGs) as a novel and environmentally friendly corrosion inhibitor. The oily fraction obtained from decoction extraction was subjected to analysis using Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The inhibitive action of SCG extract on the corrosion of copper in a 3 wt% NaCl solution was studied via potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The research findings elucidate that the extract derived from SCGs functions as a cathodic inhibitor, primarily impeding the diffusion of oxygen molecules towards the copper substrate. Notably, the inhibitory effectiveness exhibits an improvement with ascending concentrations of the SCG extract. This augmentation culminates in a remarkable 96% inhibition efficiency when the SCG extract concentration reaches 0.6 g/L. Furthermore, it is observed that the SCG extract undergoes adsorption onto the copper surface, a phenomenon that conforms to the Langmuir adsorption isotherm.