The present study was conducted to evaluate the anticorrosive and antioxidant activities of essential oil from Withania frutescens L. In the present study, the extraction of Withania frutescens L. essential oil (Wf-EO) was conducted using hydrodistillation before being characterized by gas chromatographic analysis (GC/MS) and flame ionization detector (GC/FID). Four bioassays were used for antioxidant testing including 2,2-diphenyl-1-picrylhydrazyl (DPPH), total antioxidant capacity (TAC), ferric reducing antioxidant power (FRAP), and β-carotene bleaching. The inhibiting effect of Wf-EO on the corrosion behavior of mild steel in 1.0 M HCl was conducted by using polarization curves and electrochemical impedance spectroscopy techniques. The yield of Wf-EO was 0.46% including 175 compounds identified by GC-MS. The oil was mostly constituted of camphor (37.86%), followed by thujone (26.47%), carvacrol (6.84%), eucalyptol (3.18%), and linalool (2.20%). The anti–free radical activity of Wf-EO was 34.41 ± 0.91 μg/ml (DPPH), 9.67 ± 0.15 mg/ml (FRAP), 3.78 ± 0.41 mg AAE/g (TAC), and 89.94 ± 1.44% (β-carotene). The Wf-EO showed potent antioxidant activity in all bioassays used for testing. The anticorrosion activity, polarization curves as well as EIS diagrams indicated that the Wf-EO exhibited anticorrosive properties and reacted as a suitable corrosion inhibitor in an acidic medium.

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The synergetic effects between hydroethanolic extracts of A. visnaga HE (AV) and Z. mays hairs HE (ZM) on corrosion of mild steel in 1 M HCl solution was investigated at 298 K by two techniques: potentiodynamic polarization (PP) methods (Tafel and Stern & Geary) and electrochemical impedance spectroscopy (EIS). The mixture of HE (AV)/HE (ZM) acted as an efficient corrosion inhibitor and its inhibition efficiency increased with concentration up to 96.55% at 0.01 gL−1 HE (AV)/0.2 gL−1 HE (ZM). The polarization curves revealed that the mixture acted as a mixed-type inhibitor, with anodic predominant action. The EIS studies were fitted by the (Rs + CPEdl)/(Rct + CPEf/Rf) equivalent circuit model. The kinetic parameters were in favor of a physisorption character of adsorption of HE (AV)/HE (ZM) components onto the mild steel surface. The influence of exposure time on the efficiency of mixture extract was investigated. Scanning electron microscopy (SEM/EDX) analyses confirmed the formation of a protective adsorbed film upon the mild steel surface.

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