Inter-component synergetic corrosion inhibition mechanism of Passiflora edulia Sims shell extract for mild steel in pickling solution: Experimental, DFT and reactive dynamics investigations

Green components (PESE) were extracted from Passiflora edulia Sims shell for alleviating the corrosion of mild steel (M-steel) during acidic pickling from eco-friendly and waste-cycling perspectives. Constituents prevailing in PESE were confirmed by physicochemical identifications. Weight loss, electrochemical, surface and solution analyses were employed to assess the anticorrosive efficacy of PESE for M-steel in 1 M HCl medium. PESE emerged the temperature- and concentration-dependent inhibitory effect on M-steel; the inhibition efficiency augmented with the increase in PESE dosage under a constant temperature; while, elevating temperature improved the anticorrosive capacity with an efficiency of 95.82% with 0.5 g/L PESE in HCl solution at 328 K. Electrochemical assays indicated the simultaneous inhibition of anodic and cathodic reactions over M-steel with PESE, which increased the charge transfer resistance due to adsorption. Owing to the isolation of PESE layer, the surface morphology of M-steel was maintained with the restrained increase in microroughness; besides, the chelation between iron oxides and PESE constituents reinforced the protection efficacy of adsorbed layer. Electronic-/atomic-scale modellings in-depth revealed the anticorrosive mechanism of PESE, in which interactions were captured among the proposed compounds. Overall, favorable adsorption, chelation with corroded species and inter-component synergy constituted the anticorrosive capacity of eco-friendly PESE.