Corrosion and scaling inhibition effects of Passiflora edulis Sims peel extract in simulated circulating cooling water: Experimental and theoretical insights

Abstract

Passiflora edulis Sims peel extract (PESPE) is a biodegradable substance derived from agricultural waste. In this study, we tested PESPE as a corrosion and scale inhibitor in simulated circulating cooling water (SCCW) and its effect on CaCO3 scale formation via static scale inhibition. The chemical composition and microstructure of CaCO3 scale were analyzed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM). The ability of PESPE to inhibit the corrosion of mild steel (MS) in SCCW was investigated via electrochemical tests and microscopic analyses. PESPE exhibited excellent performance in inhibiting both CaCO3 scale formation and MS corrosion, with inhibition efficiencies of 93.5% and 85.0%, respectively. PESPE converted the stable CaCO3 deposits into unstable, flocculent, and fine particles, decreasing their size from 57 to 2 μm. Furthermore, it acted as an anode-type corrosion inhibitor for MS, with its corrosion inhibition efficiency being positively correlated with its concentration. The active components of PESPE adsorb onto the MS surface to form a protective film; the synergistic adsorption behavior of the active components was confirmed via density functional theory (DFT) and molecular dynamics (MD) simulations. Our findings prove that PESPE is a sustainable alternative to conventional chemical inhibitors.