Characterization of bis-[triethoxysilylpropyl] tetrasulfide layers on aluminum based on water-based silanization solution

In this work, a water-based silanization solution was prepared using a biphasic hydrolysis system composed of 85% (V/V) water and 15% (V/V) bis-[triethoxysilylpropyl] tetrasulfide (BTESPT)/n-heptane/ethanol mixture for efficiently coating aluminum with silane layer against corrosion. The BTESPT-based coatings on several pretreated aluminum samples were characterized by scanning electron microscopy and X-ray energy dispersive spectroscopy, and their electrochemical behaviors were assessed in 0.1 M NaCl neutral solution by means of electrochemical impedance spectroscopy and Tafel polarization. The BTESPT-based coating of about 180 nm thick was found to be uniform and compact, and the maximum corrosion resistance of 106 Ω of the BTESPT-treated aluminum samples was observed, which is larger than that of bare aluminum by two orders of magnitude. Durability tests in NaCl solution demonstrated that the BTESPT coating can provide superior protection of alumina substrate from corrosion for 10-day immersion in the corrosive media.

► Water-based silanization solution prepared using a biphasic hydrolysis system.
► Silane layers with thickness of about 180 nm were uniform and compact.
► Water-based silane layers as alternative to anticorrosion chromate coatings for Al.
► Excellent anticorrosion protection observed after 10-day immersion in corrosive medium.