Mechanism of corrosion protection in chloride solution by an apple-based green inhibitor: experimental and theoretical studies

Preservation of metals in infrastructures and other assets requires cost-effective and sustainable solutions such as green corrosion inhibitors. This study assesses an apple pomace-derived green inhibitor synthesized by an innovative zero-waste method. Electrochemical measurements revealed the high performance of this liquid extract in reducing the corrosion of carbon steel in NaCl brine. The chemical composition of this inhibitor was characterized by liquid chromatography mass spectroscopy (LC-MS) to shed light on the corrosion inhibition mechanism. Based on LC-MS analysis, the results of surface analysis were interpreted. Specifically, the major corrosion inhibitor agent in the apple pomace extract was determined as C 26 H 50 NO 7 P (1-Linoleoyl-sn-glycero-3-phosphocholine), which can adsorb onto the steel surface to form a barrier layer and serve as a blocker of active anodic sites. Further study showed that the apple extract adsorption follows the Langmuir isotherm, and physical adsorption is dominant (vs. chemical adsorption). Theoretical calculations using quantum chemistry proposed a physisorption mechanism for the protection of steel by C 26 H 50 NO 7 P molecules. Graphical abstract