Eco-friendly corrosion inhibitor for mild steel in acidic media

Abstract

In recent decades, green chemistry has become a tool for sustainable growth in a variety of sectors, and the reorientation of the use of environmentally friendly alternatives is gaining attention in the field of corrosion protection. In this context, Prunus Dulcis (PD) leaf (Almond) extract, has been assessed as a potential green inhibitor for mild steel corrosion in 0.5 M H3PO4 and 0.5 M H2SO4 solutions at 30°C by electrochemical impedance spectroscopy (EIS) technique and potentiodynamic polarization curves measurements. Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectroscopy (GC-MS) results revealed that PD leaf extract contains carbonyl groups, aromatic rings, and double bonds as well as nitrogen containing compounds that make it a prospective corrosion inhibitor for mild steel. Polarization curves measurements indicated that PD is classified as a mixed type inhibitor in 0.5 M H3PO4 solutions while a cathodic type inhibitor in 0.5 M H2SO4 solutions. Nyquist plots revealed that the dissolution process occurs under activation control. The impedance responses indicated that the corrosion process occurs under activation control. To determine the mechanism of inhibition of PD leaf extract, different adsorption isotherms including Langmuir, Kinetic-thermodynamic, Flory-Huggins, and Temkin model were studied. The formation of the activated complex is an endothermic association rather than a dissociation process, according to thermodynamic characteristics. Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) proved that the inhibitive performance of PD leaf extract could be ascribed to the physical adsorption of the extract active ingredients forming a protective barrier on mild steel surface. PD leaf extract is more effective as a corrosion inhibitor for mild steel in 0.5 M H3PO4 than in 0.5 M H2SO4 solutions. In brief, our results show that PDF leaf extract is a new, ecologically safe, and effective corrosion inhibitor for the protection of mild steel in acidic media.