Capparis spinosa L. leaves extract as a novel eco-friendly antioxidant and corrosion inhibitor for St37 steel in H2SO4 medium

Abstract

Eco-friendly inhibitors have gained great research interest during the past decades. Natural-based corrosion inhibitors are produced from renewable sources and concurrently offer high performance and low environmental impact. In this work, ethanol extract of Capparis spinosa L. leaf was employed to impede St37 steel corrosion in 1 M H 2 SO 4 for the first time. The corrosion inhibition capacity of Capparis spinosa L. has been tested through multiscale assay techniques, i.e. gravimetric measurements, electrochemical analysis, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX), potentiodynamic polarization tests and Fourier transform infrared (FTIR). The liquid-solid ratio, extraction temperature and extraction time were optimized to extract antioxidant phenolic compounds from Capparis spinosa L. leaf using a Doehlert experimental design to attain the optimum concentration of each extract. High Performance Liquid Chromatography–Diode Array Detection (HPLC–DAD) was employed to identify the major components of Capparis spinosa L. extract (CSE) at optimal extraction conditions. Secondly, CSE was evaluated on the corrosion rate at different concentrations, temperatures, and times. Experimental results revealed that the CSE can be considered as good green inhibitor. Depending on electrochemical experiments, when CSE is present, corrosion current densities are highly reduced. CSE acts as a mixed-type inhibitor, effectively reducing the corrosion of St37 steel surfaces in 1 M H 2 SO 4 . At a concentration of 500 ppm CSE and 60 °C, a high inhibition efficiency of 95.63 % was achieved. Surface analysis was carried out by FT-IR and SEM-EDX confirming that the St37 steel protects from corrosion. • Natural-based corrosion inhibitors offer high performance and low environmental impact. • Ethanol extract of Capparis spinosa L. leaf effectively inhibits steel corrosion. • Using experimental design optimal extraction of antioxidant phenolic was achieved. • CSE acts as a mixed-type inhibitor.