Corrosion inhibition of aluminum by novel phthalocyanines in hydrochloric acid solution

The corrosion inhibition characteristics of quaternized 1,(4)-tetrakis[(2-mercapto)pyridine]phthalocyanine (I) and 2,3-octakis[(2-mercapto)pyridine] phthalocyanine (II) on aluminum in 0.1 M HCl solution has been studied by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The maximum inhibition efficiency was obtained for compound I with two-electrochemical techniques applied. Langmuir isotherm fits well the experimental data. The inhibition efficiency increases with increase in the phthalocyanine concentration, but decreases with an increase in temperature. The phthalocyanines act predominately as cathodic inhibitor.