Chemical and Electrochemical Investigations of L- Arginine as Corrosion Inhibitor for Steel in Hydrochloric Acid Solutions

The corrosion inhibition effect of L-arginine has been used as possible corrosion inhibitor for steel in 1.0 M HCl. Several chemical (weight loss) and electrochemical (potentiodynamic polarization, electrochemical impedance spectroscopy, EIS and electrochemical frequency modulation, EFM) measurements have been used. Data obtained from chemical and electrochemical measurements were in good agreement with the results obtained from EFM.Tafel polarization studies have shown that L-arginine affects both the cathodic and anodic corrosion processes and thus it acts as mixed-type inhibitor. The results of EIS indicate that the value of constant phase elements, CPEs tends to decrease and both charge transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. This result can be attributed to increase of the thickness of the electrical double layer. A comparative study between EFM and other conventional corrosion monitoring techniques has been performed. EFM was used as an effective method for corrosion rate determination in corrosion inhibition studies. By using EFM measurements, corrosion current density was determined without prior knowledge of Tafel slopes. Data obtained using EFM, were compared to that obtained from other chemical and electrochemical techniques and found to be comprable. The measurements demonstrated that under the chosen experimental conditions L-arginine offers sufficient protection against steel corrosion in 1.0 M HCl solutions