An Experimental and Theoretical Study of Biodegradable Gemini Surfactants and Surfactant/Carbon Nanotubes (CNTs) Mixtures as New Corrosion Inhibitor

Abstract

Inhibition performance of noncovalent functionalization of carbon nanotubes (CNTs) with biodegradable gemini surfactants on mild steel surface in 2 M hydrochloric acid solution was examined by potentiodynamic polarization, electrochemical impedance spectroscopy and quantum chemical calculations. Ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis, Raman analysis, and zeta-potential (Z-potential) measurements are also applied to discuss the stability of studied solutions. Ester-containing cationic surfactants; monomeric betainate, dodecyl esterquat gemini (ET), and dodecyl betainate gemini (BT) were used as potentially superior noncovalent functionalization agents for CNT-based formulations. For the first time, the anticorrosive efficiency of these surfactants on mild steel was investigated. The noncovalent functionalization of CNTs with ester-containing surfactants showed more appropriate inhibition properties at higher surfactant concentrations as a result of further dispersing ability. The best inhibition efficiency (IEE = 93%) is reported for BT (2.5 mM)-suspended nanotubes, while the effectiveness is decreased (IEE = 12%) dramatically at low concentration (0.1 mM). Surface observations are also employed to verify the corrosion protection of mild steel covered with noncovalent functionalization of CNTs. Density functional theory was employed for quantum chemical calculations, and a good correlation between experimental data and theoretical data has been obtained.