Self-Healing Effect of Hybrid Sol-Gel Coatings Based on GPTMS, TEOS, SiO2 Nanoparticles and Ce(NO3)(3) Applied on Aluminum Alloy 7075-T6

Aluminum alloy AA7075-T6 is most commonly used in the aircraft and automotive industries. Due to the presence of intermetallic particles, AA7075-T6 is susceptible to localized corrosion in chloride solutions. In the present work multilayer hybrid sol-gel coatings, based on silane precursors 3-glycidyloxypropyl(trimethoxysilane) (GPTMS) and tetraethoxysilane (TEOS), were used to protect AA7075-T6 from corrosion. To enrich the barrier properties of the coating, SiO2 nanoparticles were added to the GPTMS/TEOS sol-gel solution. Inhibition and a self-healing effect were achieved by doping Ce(NO3)(3) in the coating. A multi-layer system was applied on the substrate composed of a first layer doped with Ce(NO3)(3) and the second, undoped sol-gel layer. The addition of cerium increases the lifespan of hybrid sol-gel coating and has a role in self-healing if it is locked within the first layer of the multilayer coating. The self-healing effect was confirmed by immersion of unscribed and scribed coated substrates in 0.1 mol/L NaCl by using the immersion test, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy with chemical analysis. (c) The Author(s) 2018. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License.