Experimental and Theoretical Studies of Mild Steel Corrosion Inhibition in Phosphoric Acid Using Tetrazoles Derivatives

The electrochemical behavior of mild steel in phosphoric acidic solutions was investigated in the absence and presence of three heterocyclic tetrazoles derivatives using polarization and electrochemical impedance techniques. The corrosion rate is affected by both acid and inhibitors concentration. Inhibitors reduce the corrosion rate values by suppression of anodic dissolution of steel rather than the cathodic process of hydrogen evolution. Corrosion potential values were shifted to positive direction. Addition of inhibitors did not change the mechanism of corrosion process, which indicates that these compounds act by forming a film on metal surface. Impedance measurements showed that the charge transfer resistance increases and the double layer capacity decreases with addition of inhibitors. Charge transfer resistance increased with time. Maximum inhibitor efficiency was 71.5%, which leads to conclude that the studied inhibitors represent moderate anticorrosion materials. Quantum chemical investigations were also used to optimize the chemical structure of inhibitors.