Effects of Tannic Acid on the Corrosion Inhibition Behavior of Copper in Acidic Red Soil Simulation Solution

The effect of tannic acid on the corrosion behavior of pure copper grounding materials in an acidic red soil simulation solution was studied using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results show that when the mass concentration of tannic acid was 0.1-4.0 g/L, its corrosion inhibition efficiency on copper increased with the increase of tannic acid mass concentration. Adding tannic acid could effectively inhibit the corrosion reaction of copper. In the soil simulated solution system, tannic acid belonged to a cathodic corrosion inhibitor. The results of the Mott Schottky curve analysis indicat that in the acidic red soil simulation solution, the film formed on the copper surface had p-type semiconductor properties. As the concentration of tannic acid increased, the acceptor concentration decreased, and the corrosion resistance of the film layer on the copper surface was strong. The adsorption of tannic acid molecules on the copper surface tended to follow the Langmuir adsorption model. When the mass concentration of tannic acid was 0.1-4.0 g/L, its adsorption free energy on the copper surface was less than 0 and greater than -40 kJ/mol. Tannic acid undergoed a spontaneous physical adsorption process on the copper surface.