Corrosion Inhibition of Alloy Al-Cu-Mg by Lanthanum Chloride in 0.5 M NaCl

This work studies the corrosion behavior of Al-Cu-Mg alloy in 0.5M NaCl with rare earth salt inhibitor, lanthanum chloride (LaCl3). LaCl3 concentrations used are: 100, 200, 400, 800 and 1000 ppm. The study was carried out by potentiodynamic measurements, impedance electrochemical spectroscopy, cyclic voltametry and gravimetric method. The results obtained show that lanthanum acts as cathodic inhibitor by the reduction of the Tafel cathodic slopes. The inhibition mechanism can be explain by the hydroxide formation between the cations La(III) and ions OH- .This hydroxide precipitates forms a passive film on the alloy surface in the chlorinated medium. The inhibiting effectiveness reaches 89.09 % for 1000 ppm of LaCl3.