Towards sustainable corrosion inhibition: A combined experimental and computational study of ethyl triphenyl phosphonium iodide on aluminium in acidic medium

Abstract

The quest for innovative and effective corrosion inhibitors, alongside advanced methodologies for corrosion monitoring and quantification, remains pivotal across diverse industrial domains. This study explores the potential of ethyl triphenyl phosphonium iodide (ETPI) as a high-performance corrosion inhibitor for aluminium in a 0.5 M hydrochloric acid medium. Employing three complementary experimental techniques—weight loss analysis, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS)—the research demonstrates consistent and reliable results across varying temperatures and ETPI concentrations. A notable decline in inhibition efficiency was observed at reduced ETPI concentrations and elevated temperatures, underscoring the dynamic interplay between environmental factors and inhibitor performance. Crucially, the adsorption behavior of ETPI aligns with the Flory-Huggins adsorption isotherm, with thermodynamic parameters (∆G⁰_ads, ∆H⁰_ads, ∆S⁰_ads, and K_ads) and kinetic activation energy (E_a) providing deeper insights into the adsorption mechanisms. Additionally, quantum chemical simulations reveal the molecular attributes of ETPI responsible for robust chemisorption interactions with the aluminium surface. These findings are further validated by scanning electron microscopy (SEM) images and energy-dispersive X-ray (EDX) spectroscopy, which confirm the inhibitor's efficacy and surface-protective properties.

The study not only reinforces ETPI’s viability as an effective corrosion inhibitor but also provides a comprehensive framework combining experimental, thermodynamic, and theoretical approaches, paving the way for the development of next-generation corrosion mitigation strategies.