Self-forming barrier layer for carbon dioxide corrosion protection of mild steel in NaCl solution containing hydroxychavicol isolated from Piper betle L. leaf

[Display omitted] •Hydroxychavicol was isolated from the Piper betle − leaf water extract and firstly employed as a corrosion inhibitor.•Hydroxychavicol acted as a mixed-type inhibitor with a greater inclination towards anodic characteristics.•The capability to shield mild steel from carbon dioxide corrosion is due to the protective film formation.•Hydroxychavicol possibly inhibited localized corrosion due to random distribution of corrosion depth. Hydroxychavicol compound was isolated from Piper betle L. leaf and identified via preparative high performance liquid chromatography (Prep-HPLC) and nuclear magnetic resonance (NMR) spectroscopy. Hydroxychavicol compound was demonstrated to be a potential inhibitor for mild steel corrosion in carbon dioxide-containing environments due to the formation of a barrier layer on the steel surface. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results indicated that the inclusion of hydroxychavicol in the aggressive environment made steel surfaces more homogeneous and smoother with a rough mean square roughness of 7.78 nm, whereas the steel surface was severely corroded in the blank solution. Moreover, X-ray photoelectron spectroscopy (XPS) results showed an enrichment of hydroxychavicol species combined with iron oxides and hydroxides on the mild steel surface. This can lead to the creation of a protective layer on the mild steel surface, thereby enhancing corrosion protection and localized inhibition. The work suggested a novel approach to isolate corrosion inhibitors from natural products, particularly agricultural by-products for mild steel in carbon dioxide and chloride ion environment with high inhibition performance.