Development of processes to deposit hybrid coatings using Silanes and zirconium and titanium nano composites

Abstract

Growing concern with sustainable development, along with greater awareness regarding the preservation of the environment, It has stimulated research in order to find environmentally friendly replacements for efficient systems to hexavalent chromium (Cr6 +), which are used as pre-treatment of aluminum and its alloys. These conventional treatments offer excellent protection against corrosion, provide good base for paints, are cheap and relatively easy to apply. However, since the last decades, environmental and health restrictions have become more severe, which requires the replacement of these treatments with other alternatives that are ecologically correct and non-aggressive to human health. In the above, the use of hybrid coatings derived from silanes, obtained by the sol-gel process, has been presented as one of the most investigated alternatives for the substitution of the pre-treatments based on Chromium. Such coatings form a compact polymeric matrix on the metal surface forming an effective barrier against aggressive species, they may also be used as primers for organic coatings. Nowadays on the market there are many alternatives to conventional treatments, including the use of silanes as well as baths containing nano-composites, however they do not show active corrosion protection when compared to baths containing chromate. The purpose of this project is to compare two coatings based on silanes, with addition of Zirconium or Titanium nanocomposites as a substitute for chromium as a protective action for Aluminum and its alloys used in the aeronautics and architecture industry respectively. To obtain the coating on the metal surface of the dip-coating method is used and its parameters are controlled. Against in this context, the screen project has as main objective develop, obtain and characterize the adhesion, morphology, microstructure and evaluate how much the resistance to corrosion, coatings based on silanes with addition of nano-composites to meet a requirement of the market and, in addition, meet the most stringent environmental standards. These are innovative processes totally geared to comply with the environmental guidelines, significantly reducing the volume of surface treatments effluents with consequent reduction of inputs. (AU)