Corrosion inhibition of aluminum alloy AA 2014 by rare earth chlorides

The effect of LaCl3 and CeCl3 inhibitor additions in 3.5% NaCl solution on the corrosion behaviour of aluminum alloy AA2014 has been investigated. Four different concentrations (250, 500, 750 and 1000 ppm) of LaCl3 and CeCl3 were studied. The polarization resistance increased significantly and the corrosion rate decreased by an order of magnitude with the addition of 1000 ppm of LaCl3 and CeCl3, with maximum decrease noticed for CeCl3. EIS studies showed that there was a significant increase in overall resistance after addition of 1000 ppm LaCl3 and CeCl3, when compared to the case without inhibitor. The double layer resistance and film resistance increased after inhibitor addition. Scanning electron microscopy confirmed formation of precipitates of oxide/hydroxide of lanthanum and cerium on cathodic intermetallic sites, which reduced the overall corrosion rate.