The inhibiting effect of cerium chloride and lanthanum chloride on the corrosion of 2219-T87 aluminium alloy (AA2219-T87) in seawater was investigated by potentiodynamic polarisation, electrochemical impedance spectroscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. It is found from potentiodynamic polarisation curves that cerium chloride and lanthanum chloride serve as cathodic inhibitors. The decrease in charge transfer resistance after the addition of rare earth chlorides further confirmed their inhibition on AA2219-T87 towards seawater environment. Scanning electron microscopy and energy dispersive spectroscopy analysis revealed the formation of cerium and lanthanum hydroxide/oxide deposits on second phase intermetallic particles (Al2Cu) confirmed their cathodic inhibition. Cerium chloride exhibited better inhibition efficiency than lanthanum chloride due to the lower solubility of cerium hydroxide.
Keywords: AA2219-T87; Rare earth inhibitors; Potentiodynamic polarisation; Electrochemical impedance spectroscopy; Scanning electron microscopy |