Characterization of self-assembled bis-[triethoxysilylpropyl] tetrasulfide silane films on surface of 2A12-T6 aluminum alloy

Bis-[triethoxysilylpropyl] tetrasulfide silane films were self-assembled on surface of 2A12-T6 aluminum alloy for corrosion protection. The structure of the formed silane films was investigated by using Fourier transform infrared (FTIR) spectroscopy, and the corrosion performance of the film was evaluated by electrochemical potentiodynamic polarization tests in 3.5% NaCl solution. Compared to the untreated case, both the cathodic and anodic reactions of Al 2A12-T6 treated with the silane films are inhibited obviously. For the film on the surface of Al 2A12-T6 aged at room temperature the corrosion current density is reduced by more than 1 order of magnitude, which is due to the hydrogen bonding between silane molecules and surface of 2A12-T6. For the film on the surface of Al 2A12-T6 cured at temperature of 120 degrees C for 40 min the silane molecules are cross linked through SiOSi, which is closely linked to Al 2A12-T6 surface through formation of SiOAl. The corrosion current density is reduced by more than 2 orders of magnitude. There exist more hydrogen bonded hydroxy groups in the cured film dipped for 10 min in the prepared silane solution than that dipped for 2 s to 1 min.