氯化镧对2024铝合金缝隙腐蚀的缓蚀作用

为了降低2024铝合金在海水中的缝隙腐蚀敏感性,采用浸泡和动电位极化、电化学阻抗等研究了氯化镧(LaCl3)对该铝合金缝隙腐蚀行为的影响,并通过原子力显微镜对缝隙试样内、外腐蚀产物膜的形貌进行了观察.结果表明:当海水中LaCl3的质量浓度超过2.0 g.L-1以后,它能有效地减缓2024铝合金在海水中的缝隙腐蚀.这主要是因为LaCl3减缓了缝隙的阴极反应速率,降低了缝隙内、外的氧浓度差,且缝隙内、外生成的均匀致密的腐蚀产物膜降低了Cl-侵蚀性,这些因素抑制了缝隙的萌生与扩展,提高了2024铝合金在海水中的抗缝隙腐蚀能力.

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 LaCl_3 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 LaCl_3 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.