Synergistic inhibition between tween 60 and NaCl on the corrosion of cold rolled steel in 0.5M sulfuric acid

The corrosion inhibition of cold rolled steel in 0.5 M sulfuric acid in the presence of tween 60 and sodium chloride (NaCl) has been investigated by using weight loss and electrochemical techniques. The inhibition efficiency increases with increasing tween 60 concentration at the same temperature, but decreases with increasing temperature studied. A synergistic effect exists when tween 60 and chloride ions are used together to prevent cold rolled steel corrosion in 0.5 M sulfuric acid at every experimental temperature. The polarization curves show that tween 60 is a cathodic inhibitor, while the complex of tween 60 and NaCl is a mixed-type inhibitor. The experimental results suggest that the presence of chloride ions in the solution stabilizes the adsorption of tween 60 molecules on the metal surface and improves the inhibition efficiency of tween 60. The adsorption of single tween 60 follows the Temkin adsorption isotherm, but the complex accords with the Langmuir adsorption isotherm. Some thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy has been calculated by employing thermodynamic equations. Kinetic parameters such as apparent activation energy and pre-exponential factor have been calculated and discussed. (C) 2004 Elsevier Ltd. All rights reserved.