Electrochemical kinetics, molecular dynamics, adsorption and anticorrosion behavior of melatonin biomolecule on steel surface in acidic medium

Electrochemical, anticorrosion and adsorption behaviour of bio-based melatonin (MEL) in 5% HCl solution was investigated by experimental and theoretical approaches. MEL was found to possess high adsorptive capacity for steel surface and inhibits the acid corrosion. With a concentration of 10 mM, inhibition efficiency of 98.3% and 88.6% were obtained at 30 °C and 60 °C respectively. Langmuir associative and dissociative models describe simultaneous physisorption and chemisorption. FTIR, SEM/EDS and quantum molecular dynamics simulations using DFT provide evidences that MEL forms adsorbed surface complex film (in the protonated form) coordinated mainly by indole ring, N(9) and O(10). The biomolecule is a promising alternative anticorrosion additive for acid wash solutions.