Corrosion Inhibition and Adsorption Mechanism of PVP for Mild Steel in 1.0 M H2SO4: Experimental and Theoretical Approach

Abstract

Aim: Corrosion of mild steel pipe line when exposed to dilute sulphuric acid is a very serious problem for people in the industry and they are in constant search of highly efficient corrosion inhibitors for acidic medium. For designing new corrosion inhibitors, a through knowledge of corrosion and adsorption mechanism is required. Background: Pitting, cracking and uniform types of corrosion are very common forms of corrosion in dilute sulphuric acid medium. A highly efficient acid corrosion inhibitor is required to minimize all these three forms of corrosion. Objective: The objective was to provide a solution for pitting, cracking, and uniform types of corrosion and to study corrosion and inhibition mechanisms so that highly efficient corrosion inhibitors can be designed. Methods: Polyvinyl pyrrolidone (PVP) was explored as a corrosion inhibitor for mild steel in 1.0 M H2SO4 by experimental and theoretical techniques. Experimental techniques used were impedance, weight loss, metallurgical microscopy, and polarization. Theoretical techniques used were DFT, MD simulation, Frontier molecular orbital, Langmuir, and Frumkin adsorption. Theoretical parameters like interaction energy, adsorption energy, Fukui function, chemical potential, electron density distribution, HOMO/LUMO eigenvalue, etc., help in understanding the mechanism of adsorption of PVP on the Fe (110) surface. Results: Experimental results were supported by theoretical studies. A linear relation was observed between PVP concentration and inhibition efficiency. A maximum of 85.92% inhibition efficiency was observed with a regression coefficient of 0.998. The pore length, the number of pits, and cracks intensity decrease with the concentration of PVP. The waste dilute H2SO4 after the weight loss study was investigated for its biocompatibility and was found to be within the acceptable limit. Conclusion: PVP was proved to be a highly efficient acid corrosion inhibitor for mild steel in 1.0 M H2SO4 medium.