Corrosion Inhibition of Copper in Nitric Acid Solution Using Some Secondary Amines

Copper corrosion inhibition in 0.1 M nitric acid (HNO₃) solution by some secondary amines, namely, dibutyl amine (C₈H₂₀N), diethyl amine (C₄H₁₁N), and diphenyl amine (C₁₂H₁₁N), was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. A significant decrease in the corrosion rate of copper was observed in the presence of the investigated compounds. The corrosion rate was found to depend on the concentration, temperature, and type of inhibitor. The adsorption of these compounds was found to follow the Temkin adsorption isotherm. Tafel polarization data indicated that the investigated amines were inhibiting both cathodic and anodic reactions. The thermodynamic activation parameters of copper dissolution in 0.1 M HNO₃ were determined and discussed. The results obtained from the three different techniques were in good agreement. Clear correlation was found between corrosion inhibition efficiency and theoretical parameters obtained from the PM3 semi-empirical method. The experimental results are supported by the theoretical data.