2',3-Dicarboxylato-4-Hydroxyazobenzene as Corrosion Inhibitor for Aluminium in Sodium Hydroxide

A study involving both weight loss and electrochemical techniques has been undertaken to understand the effect of 2‘,3- dicarboxylato-4-hydroxyazobenzene on the corrosion of Al in NaOH solution. The inhibitive effect increases with the increase in the concentration of the inhibitor. The maximum inhibition efficiency for the dye was found to be 55.72. The addition of calcium oxide of concentration, 1.0 x 103 M, increase the above maximum inhibition efficiency to 76.52. The inhibitor appears to operate through its adsorption over the metal surface and through its ability to slow down the discharge of H+ as H2 gas at the cathodic sites on the metal surface. There is no definite shift in the open circuit potential, OCP, due to increasing addition of dye without and with a particular concentration of calcium oxide. The polarisation studies revealed that the corrosion of aluminium in the presence and the absence of inhibitor was under the anodic control. The corrosion inhibition was found to be of mixed type