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Abstract :
[en] Sol-gel coatings are very promising materials to act as protective layers in the framework of chromates replacement. However, even if these layers provide passive protection and good adhesion to the substrate, they are inherently not able to protect the metal in case of coating damage. Incorporating nanocontainers (such as nanoclays or polyelectrolytes), which hold corrosion inhibitors, is often investigated in order to confer healing properties to sol-gel layer.
The objective of this work is to assess the ability of mesoporous sol-gel thin films to constitute a new type of nanocontainers for corrosion inhibitors. Indeed the porosity developed through the film has already been used in several fields to incorporate important quantity of active compounds for applications such as drug delivery1, photoelectrode in dye sensitized solar cell2... Moreover, the use of the direct inner porosity of the film as nanocontainer allows avoiding dispersion and compatibility problems observed with usual nanocontainers.
Mesoporous SiO2 coatings were synthesized using evaporation-induced self assembly method (EISA process). Different synthesis parameters (type and quantity of templating agent and ageing of the film) were considered in order to modify the pore volume and accessibility which are very important parameters for the future incorporation of inhibitor. Samples were observed with a transmission electron microscopy (TEM) to characterize the porous network (pore density and size). The pore accessibility was determined by using atomic force microscopy (AFM) and by using a quartz crystal microbalance.
Organic inhibitive solution was used to impregnate the mesoporous film and to impart active property to the sol-gel coating. Indeed corrosion inhibitor soaks into the pores due to capillarity forces and can be released in case of corrosion process. UV-visible spectrophotometry, glow discharge optical emission spectroscopy (GDOES) and Fourier transformed infrared spectrometry (FTIR) were used in order to determine the amount of corrosion inhibitor encapsulated in the mesoporous film. The morphology of the porous structure can be correlated with the incorporation efficiency of films.
