A summary of CSIC- FUNGLASS collaboration on sol-gel coatings
A. Durán, Y. Castro
Instituto de Cerámica y Vidrio, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain

Collaboration CSIC-FUNGLASS has been mainly focused in the synthesis and preparation of sol-gel coatings for different purposes, particularly for functionalization and protection of metallic substrates as well as for photocatalytic applications, all developed in the Coatings department.
The effect of surface pretreatments on the adhesion, mechanical and barrier properties of epoxy coatings was studied on steel and aluminum substrates, obtaining efficient adhesion by simple methodologies and widely available chemicals as alternative to the current industrial pre-treatments and chromate conversion layers used to protect metallic alloys.
A bio-based sol-gel epoxy anti-corrosion coating was developed using vanillin alcohol diglycidyl ether (DGEVA), an eco-friendly epoxy resin, showing excellent adhesion to the substrate, and providing long-term protection (> 60 days under immersion) of AA2024 under highly corrosive conditions.
Plasma electrolytic oxidation (PEO) films combined with sol-gel coatings were used for preparing smart self-healing protective systems to provide active and long-term protection to Mg alloys. The deposition of a first oxide layer using PEO technique was followed by a post-sealing process using a Ce-based solution and a final SiO2 hybrid sol to achieve good barrier properties. The electrochemical properties, studied in 3.5%wt NaCl solution, revealed that appropriate anodization electrolytes together with the post-treatment process result in a promising solution to control the corrosion performance.  
58S bioactive glasses were synthesized using the sol-gel method including several polyols such as glycerol, ethylene glycol, and polyethylene glycol, and deposited onto Mg alloys to prepare corrosion protecting bio-functional coatings. The 58S PEG sol-gel films are considered a promising choice for biodegradable magnesium alloy-based medical implants.
One interesting and new sol-gel synthesis was developed with polyorganosilazane/GPTMS silica coatings for corrosion-resistance system for AA2024-T3 Al alloys. Transparent films with thickness around 13 µm were obtained, the electrochemical results confirming that these coatings significantly improve the corrosion resistance of the substrate in 3.5 wt.% NaCl.
Further than developed protecting coatings on light alloys, sol-gel dip-coating was used to deposit ZnO thin films on glass substrates and silicon wafers to be used as photocatalysts, optimizing the different synthesis parameters. The best photocatalytic activity under solar radiation was shown by ZnO thin film annealed at 400ºC, accelerating the degradation of MO, one of the main water pollutants found in the effluent from the textile and paper sectors. The incorporation of silver nanoparticles to ZnO sols are currentely considered. 

Keywords: sol-gel coatings, corrosion protection, light alloys substrates, bio-functional films, photocatalytic ZnO coatings