Corrosion Inhibition of Copper Alloy of Archaeological Artefacts in Chloride Salt Solution Using Aloe Vera Green Inhibitor

Abstract

Copper alloys have long been regarded as important cultural heritage metals artefacts. They are still widely used in a variety of industries today. Nonetheless, copper alloys can corrode in harsh environments containing chloride salt. Organic inhibitors are used to suppress the corrosion of copper alloys, and the use of green inhibitors is preferred due to environmental considerations. This study focuses on the corrosion protection of copper alloy in 0.6M of sodium chloride solution in absence and presence of various concentrations of fresh inner leave gel (FILG) of aloe vera barbadensis as a green inhibitor at room temperature (RT). The research methodology applies some methods to do the study, such as open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), Scanning electron microscopy-Energy dispersive X-ray analysis (SEM-EDX), and quantum chemical calculations (QCC). Increased inhibitor concentrations resulted in high inhibition efficiency. Electrochemical polarisation exhibits around 99.9% inhibitory efficiency (IE) at a concentration of 200 ppm. It is found that as the concentration increases to 500 ppm, the IE decreases but the protective efficiency remains good. This behavior might be due to the reverse action of the protective film formed on the surface by the accumulation of the inhibitor molecules. Electrochemical measurements show shifting of the corrosion potential to more positive potential. This behavior indicates the formation of protective film on the copper alloy surface. The high IE of the FILG green inhibitor is due to the presence of various functional groups. These functional groups enhance the protective film formation and hinder the effective electron transfer rate at the interface. The QCC reveals that the FILG inhibitor's high IE is due to the increasing dipole moment and low energy gap of polarizable organic molecules. This facilitates the electron transfer between organic molecules and the copper alloy surface, enhancing the formation of protective film.