Perpustakaan Digital ITB

Corrosion inhibitor is widely used for corrosion control in industrial processes that involve solution such as in water treatment, oil & gas refineries, etc. In the last decades, the search of effective yet biodegradable corrosion inhibitor for lowcarbon steel has been a crucial topic ever since environmental issue – from using conventional inhibitior - emerges as a critical concern. To this idea, the use of natural source e.g agricultural wastes, drugs, and plant extracts have widely gained significant attention because of the presence of heterocyclic constituents from bioactive compounds that is essential as good corrosion inhibitor. Based on the fact that Indonesia is rich in tropical fruits of several species, one of which is rambutan, the corrosion inhibition performance of some phenolic compounds exist in rambutan (Nephelium Lappaceum) seed and peel extract (RSPE) was studied. Theoretical approaches using computational chemistry methods i.e density functional theory (DFT) and molecular dynamics (MD) simulation were carried out to invesitigate the inhibition mechanism at molecular level of some phenolic compounds of rambutan seed and peel on low-carbon steel in aqueous solution. DFT approach was done using B3LYP/6-311G** basis sets to reveal the reactive sites and eigenvalues of electronic parameters from the molecules studied. MD simulation was conducted at 298 K controlled by Berendsen thermostat in water solvents of 300 molecules using NVT ensemble to examine the adsorption mechanism and their interaction with the metal surfaces. To verify and validate that the simulation results reflect the real behaviour of the molecules, postprocessing and comparative study with available relevant literature were done. Based on the results, some phenolic compounds of rambutan seed and peel are soluble in water, indicating application in aqueous solution are possible. DFT-based calculation shows that all molecules are capable to interact through donor-acceptor electron with EHOMO and ELUMO eigenvalues vary from -4.9 to -6.1 eV and -1.1 to - 3.2 eV, respectively. Hereafter, MD simulation reveals that all molecules studied were able to be spontaneously adsorbed by chemisorption and physisorption onto iron surface and serve as protection layer from corrosive media at room temperature with interaction energy (Einteraction) varies from -87 to -459 kcal/mol. Finally, in accordance to the simulation results and comparative study, EHOMO and amount of oxygen atom appears to be the most appropriate descriptors to the estimation of inhibition performance and adsorption strength of C-H-O molecule, respectively.