Experimental and theoretical study of 2-mercaptopyridine as an effective eco-friendly inhibitor for copper in aqueous NaCl

The high-efficiency and non-toxic inhibitors for copper and its alloys are of great importance for reducing the corrosion rate of copper in aggressive solutions. In this work, the inhibition effect of 2-mercaptopyridine (2-MP) for copper in NaCl aqueous solution was investigated by experiment and theoretical calculation. The comprehensive experimental results showed that the surface of the copper sample was still smooth after 72 h immersion in NaCl solution containing 0.75 g/L 2-MP inhibitor, and the inhibition efficiency could reach 93.27 %. Meanwhile, the Cu N/S Cu bonds were detected by X-ray photoelectron spectroscopy and Raman spectroscopy, indicating that the 2-MP inhibitor could adsorb on the copper surface directly. The adsorption of copper by 2-MP is compatible with the Langmuir isotherm adsorption. The difference in reactivity between 2-MP and 4-MP was analyzed by quantum chemistry calculation, while molecular dynamics (MD) simulation results showed that 2-MP has better inhibition performance than 4-MP. Furthermore, the compactness and hydrophobicity of the 2-MP molecular layer were increased with a rise in 2-MP concentration, which effectively obstructed the diffusion of the water molecular and prevented the corrosive medium contact with the copper surface.