Proc. CORROSION 2015, NACE, Dallas/US 2015
In recent years coatings based on nanotechnological methods have gained increasing importance. Nanoparticles from sol-gel systems or from commercial dispersions as well as different kinds of nanocapsules may be used to produce new coating systems or to increase the protective properties of conventional coating systems. In this paper an overview of different ways of using nanoparticles for the production or modification of coating systems on metals as followed in the author's research group will shortly be shown.
On the one hand nanoparticles may be used as a coating material to obtain inorganic coatings at moderate treatment temperatures due to the high sintering activity of nanoparticles. Such coatings have been obtained on magnesium alloys using different strategies, however, a sufficient densification of the coating turned out difficult at low temperatures. On the other hand a combination of nanoparticulate layers with a chemical conversion treatment lead to quite promising results. Moreover glass-like coatings have also been used successfully on steels for oxidation protection during hot-stamping or for the formation of repair layers for technical enamels.
The modification of coating systems has been investigated especially for anodising layers on Al and Mg alloys. For Al a modified phosphoric acid anodising process has been developed including the impregnation in a nanoparticle dispersion. On Mg alloys anodising layers have been produced at comparably low voltages in an alkaline bath in combination with the electrophoretic deposition of mesoporous nanoparticles. After a suitable surface modification these particles may be loaded by corrosion inhibitors in order to provide self-healing properties.