Natural triterpenoids of Ganoderma lucidum as new, green, and effective corrosion inhibitor for steel in acidic medium: characterization, experimental and theoretical investigations

Ganoderma lucidum, a wood-decaying fungus, has been at the center of pharmaceutical research for its disease curative and preventive abilities due to its abundant antioxidant-rich phytoconstituents. Herein, we have explored its outstanding inhibition properties in the protection of steel from environmental degradation. Its triterpenoid constituents were extracted, characterized by liquid chromatography/multi-stage mass spectrometry, and applied in both experiments (electrochemical, gravimetric, 3 D optical profiling, SEM, and FTIR tests) and computation (quantum chemical calculations and molecular dynamics simulation) to reveal its metallic corrosion suppression efficacy. 36 constituent triterpenoids were effectively characterized from the extract. In comparison with corresponding electrochemical tests conducted with the crude extract of Ganoderma lucidum, an inhibition efficiency of 83.1% at 1.0 g/L was recorded for the triterpenoid extract against 93.9% for 1.0 g/L crude extract, and both extracts displayed mixed-typed corrosion inhibition properties, exhibiting improved performances with increasing concentrations and exposure time while their effects were gradually decreased with temperature increments. The potential presence of the triterpenoids was confirmed on the carbon steel surface by the surface analytical techniques, and the experimental data were in full compliance with the Langmuir adsorption isotherm model. Computational methods estimated the adsorption performances of some selected triterpenoids on Fe (110) surface. An exclusive study of the corrosion inhibition influence of triterpenoids for metal protection in an acid environment is hereby presented for the first time, and the reported results will benefit future explorations of triterpenoids in inhibitors design and synthesis.