Corrosion Inhibition Efficiency, Experimental and Quantum Chemical Studies of Neutral Red Dye for Carbon Steel in Perchloric Acidic Media

The Neutral Red (NR) has been investigated as a corrosion inhibitor for carbon steel (C-steel) in 1M perchloric acid using a weight loss method and theoretical calculations based on density functional theory (DFT). The obtained results revealed that NR is an effective inhibitor and its inhibition efficiency increases with the increasing concentration to attain 89.50 % at 5•10-3 M at 293 K. The thermodynamic parameters as enthalpy, entropy and Gibbs free energy for both dissolution and adsorption processes are calculated and discussed. Moreover, the free energy of adsorption showed that the corrosion inhibition takes place by a spontaneous physicochemical adsorption of inhibitor molecules on the C-steel surface. The results show that the calculated values of the quantum chemical parameters indicate a possible existing link between the effectiveness of the inhibitor and its electronic properties.