In-depth insight into the corrosion inhibition mechanism of an environmentally benign lignin-based corrosion inhibitor: From molecular adsorption to film reconstruction

In this work, a chemically modified sodium lignosulfonate-quaternary ammonium salt material (CM-SLS) was successfully synthesized with the corresponding yield of product reaching 66.76%, and CM-SLS was used as an environmentally benign lignin -based corrosion inhibitor for mild steel in 1.0 mol L −1 hydrochloric acid solution. The experimental results demonstrate that CM-SLS has exceptional performance relative to unmodified sodium lignosulfonate (SLS). Specifically, at the dosage of 100 mg L −1 , CM-SLS achieves maximum corrosion inhibition efficiencies of 93.49% and 83.62% at 298 K and 323 K, respectively. The CM-SLS inhibitor also exhibits better anti-corrosion capability compared with other bio-based corrosion inhibitors reported in recent years as well. Besides, the adsorption of CM-SLS molecules on mild steel surface conforms to Langmuir isothermal adsorption model. Moreover, the corrosion protection performance of the CM-SLS inhibitor enhances over time, achieving a corrosion inhibition efficiency of 95.86% after 12 h immersion. Notably, comparative analysis with the conventional organic corrosion inhibitor revealed the reconstruction behavior of the CM-SLS adsorption film. The reconstruction behavior could drive the CM-SLS adsorption film toward ordering, stabilization and higher hydrophobicity, thereby contributing to enhancing the long-term corrosion inhibition performance of the CM-SLS inhibitor. Furthermore, this study also presents the first systematic investigation into how the reconstruction behavior influences the long-term anti-corrosion performance of the CM-SLS inhibitor. Simultaneously, the impact of this reconstruction behavior is quantified by introducing the parameter conformational entropy ( ∆ S conf ). And the corrosion inhibition mechanism of the CM-SLS inhibitor is comprehensively elucidated.