Synergistic adsorption mechanism of pulsatilla chinensis root extract as an eco-friendly corrosion inhibitor for carbon steel in acidic solution.

With heightened emphasis on environmental sustainability, plant extracts have emerged as biodegradable alternatives to traditional organic corrosion inhibitors. In this study, the anti-corrosion performance of pulsatilla chinensis root extract (PCRE) for Q235 carbon steel in sulfuric acid solution was systematically investigated. The water-soluble extract was obtained from pulsatilla chinensis using an environmentally friendly ethanol extraction. Fourier transform infrared spectroscopy (FTIR) and liquid chromatography-mass spectrometry (LC-MS) analyses indicated that PCRE is abundant in saponin compounds, which possess unique polyoxygenated conjugated structures that consequently facilitate the formation of a protective layer on Q235 carbon steel surface. Correspondingly, electrochemical experiments demonstrated that PCRE achieved a high corrosion inhibition efficiency of 95.3 % at 298 K. Additionally, surface characterization techniques confirmed that PCRE significantly mitigated corrosion on Q235 carbon steel. Further mechanistic insights from quantum chemical calculations identified oxygen atoms in carboxyl/hydroxyl groups as crucial coordination sites for iron. Collectively, these results indicate that the protective layer is formed through physicochemical synergistic adsorption, involving both electrostatic interactions and the formation of coordination bonds. Consequently, PCRE has been identified for the first time as an efficient and environmentally benign corrosion inhibitor. Notably, its excellent water solubility of PCRE enables direct application in industrial pickling systems, while its unique multi-oxygen conjugated structure provides valuable insights into the molecular design of corrosion inhibitors based on such structural features.