Zea mays bracts extract as an eco-friendly corrosion inhibitor for steel in HCl pickling solution: Experimental and simulation studies

Abstract

Active phytochemicals with unique electron structures can adsorb on metal surfaces and effectively mitigate metal corrosion. Recently, plant extracts have garnered significant attention as green and renewable corrosion inhibitors. In this study, the abundant agricultural byproducts, namely Zea mays bracts, were used as the extract raw materials, and Zea mays bracts extract (ZMBE) was served as an eco-friendly corrosion inhibitor for mild steel (MS) in 1 M HCl pickling solution. The organic substances in ZMBE were analyzed via ultra-high performance liquid chromatography- quadrupole time-of-flight mass spectrometry (UPLC-QTFMS). The interaction between the active functional groups and MS was investigated using Fourier transform infrared (FT-IR) and ultraviolet–visible (UV–visible) spectroscopy and X-ray photoelectron spectroscopy (XPS). The corrosion inhibition behavior was scrutinized through potentiodynamic polarization (PDP) curves and electrochemical impedance spectroscopy (EIS). The results show that functional groups such as aromatic rings, double bonds, and hydroxyls successfully adsorb on the MS surface to form the protective films. ZMBE exhibits a mixed-type corrosion inhibition with a “geometric coverage” effect. The corrosion inhibition efficiency (η) increases with ZMBE concentration and solution temperature, the optimum η with 5.0 g·L−1 ZMBE at 318 K is 96.2 %. The adsorption of active ingredients follows the Langmuir and El-Awady isotherms. Density functional theory (DFT) and molecular dynamics (MD) simulations prove the synergistic effect of complex components in ZMBE and the corrosion inhibition mechanism. ZMBE is a promising acid pickling corrosion inhibitor with broad application prospects.

Keywords

• Plant corrosion inhibitor
• Zea mays bracts
• Ultrasonic extraction
• UPLC-QTFMS
• Mild steel