Inhibition effect of different concentrations of potassium folate (green inhibitor) on copper corrosion in aerated Na2SO4 solutions in the temperature range (15-55 degrees C) was investigated by using potentio-dynamic polarization and electrochemical impedance spectroscopy technique. The polarization curves showed that the addition of potassium folate inhibits copper corrosion as a result of physical adsorption of folate anions on the copper surface. The folate anion acts as an anodic-type inhibitor. The inhibition efficiency increases with increasing the folate anion concentration but decreases with increasing Na2SO4 concentration and temperature. The adsorption of folate anions on copper surface follows Flory-Huggins isotherm and kinetic-thermodynamic model. The thermodynamic parameters for corrosion and adsorption processes in the absence and presence of the inhibitor were calculated and discussed. Effect of immersion time on the performance of the inhibitor was also tested in this investigation. (C) 2010 Elsevier B.V. All rights reserved.