Inhibition of lanthanum chloride on the crevice corrosion of 2024 aluminum alloy in seawater

To reduce the susceptibility of crevice corrosion of 2024 aluminum alloy in seawater,the effect of LaCl₃ on the crevice corrosion behaviour of the alloy was investigated by immersion,potentiodynamic polarization and electrochemical impedance spectroscopy.The micrographs of corrosion product films formed on the inside and outside of crevice samples were observed by atomic force microscopy.The results show that when the concentration of LaCl₃ in seawater is in excess of 2.0 g·L^-1,the crevice corrosion may be inhibited obviously.It is because that the cathodic reaction rate of crevices is decreased and the oxygen concentration difference between the inside and outside of crevices is reduced.Moreover,the uniform corrosion product film formed on the inside and outside of crevices blocks the aggressiveness of Cl^-.The initiation and propagation of crevice corrosion are restrained by these factors,and thus the crevice corrosion resistance of 2024 aluminium alloy in seawater is improved.