Changes of Corrosion Electrochemical Behavior of Cerium Nitrate Doped GPTMS/TEOS Silane Hybrid Films with Immersion Time

Silane-based organic-inorganic hybrid films doped with cerium nitrate were prepared on LY12 aluminum alloy by sol-gel method using γ-glycidoxypropyltrimethoxysilane (γ-GPTMS) and tetraethylorthosilicate (TEOS) as precursors.The evolution of corrosion resistance of the Ce-doped silane-based hybrid coating with immersion time in 3.5% NaCl solution was investigated by polarization curve and electrochemical impedance spectroscopy (EIS) measurements.The results indicated that the polarization resistance values of the Ce-doped silane-based hybrid films decreased slowly with the increase of immersion time,and was still distinctly greater than that of aluminum substrate after 183 h of immersion.The pitting potentials of the Al alloy presented a variation of decreasing,then increasing and finally decreasing during immersion in NaCl solution.In the first period of immersion,the obvious capacitive behavior in high frequency range of EIS could be observed.The low frequency impedance values remained approximately constant in immersion from 69 h to the end of the experiment.The above changes were related to the self-healing ability of cerium salt doped in the silane hybrid films.