Self-Assembled Monolayers of Ponceau 4R as a Green Copper Corrosion Inhibitor in NaCl Solution

The inhibitory behavior of Ponceau 4 R (an important industrial food dye) on the corrosion of copper surface in 3.5% NaCl solution was studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Fourier transform infrared (FT-IR) spectroscopy. Polarization curves indicated that the self-assembled monolayer of Ponceau 4 R acts as a mixed inhibitor. The adsorption of inhibitors was well fitted to the Langmuir isotherm and the thermodynamic parameters (Kads, ∆G^0 ) were also calculated and discussed. The inhibition efficiency of ponceau 4 R film reached 99.5% under optimized conditions and the standard Gibbs energy of 31.1 kJ/mol indicated that the adsorption mechanism of the self-assembled monolayer of Ponceau 4 R on copper was a mixed mode of physical and chemical adsorption. The obtained results revealed that other food dyes containing functional groups such as hydroxyl, sulfonyl, aromatic rings and especially azo groups can act as green inhibitor for corrosion of copper in neutral sodium chloride solutions.