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The purpose of this study is to evaluate the corrosion retardation properties of methylene blue on carbon steel in hydrochloric acid solutions.

The corrosion inhibition property of methylene blue on carbon steel was investigated by hydrogen evolution technique (gasometric technique) and weight loss measurements at 303 K and 333 K in hydrochloric acid solutions.

The results revealed that methylene blue inhibited the corrosion carbon steel, and the inhibition efficiency was temperature dependent. The maximum inhibition efficiencies were 88% at 303 K and 79.2% at 333 K. The corrosion data was consistent with the Langmuir adsorption isotherm which posits that the methylene blue molecules adhered to the metal substrate. The corrosion kinetics followed the first-order kinetic reaction equation. The activation energy (Ea) values ranged from 45.6 to 81.7 kJ/mol and indicated physical adsorption.

This paper provides new information on the possible application of methylene blue as corrosion inhibitor for carbon steel.

This study aims to develop eco-friendly corrosion inhibitors for aluminum in acidic media by evaluating the corrosion inhibition properties of corn leaf extract (CLE) using response surface methodology (RSM) and experiments.

The RSM was combined with experiments to evaluate the corrosion inhibition properties of CLE on aluminum in acid media.

The effectiveness of the inhibition increased with increasing inhibitor concentration and time but decreased with increasing temperature. The corrosion inhibition mechanism revealed the corrosion process is spontaneous exothermic physical adsorption. Thermodynamic parameters revealed an activation energy between 32.1 and 24.7 kJ/mol, energy of adsorption between −14.53 and −65.07 and Gibbs free energy of −10.12 kJ/mol which indicated the CLE exothermically spontaneously physisorbed. A model was generated to estimate the effect of the process parameters (inhibitor concentration, reaction time and temperature) using the RSM. Optimization of the process factors was also carried out using the RSM. The percentage inhibition efficiency obtained experimentally (85.61%) was closely comparable to 84.89% obtained by the theoretical technique (RSM). The SEM observations of the inhibited and uninhibited Al samples demonstrated that CLE is an effective corrosion inhibitor for aluminum in acid media.

Results herein provide novel information on the possible application of CLEs as effective eco-friendly corrosion inhibitors.