Corrosion protection with synergistic LBL/Ormosil nanostructured thin films

Abstract

Stratified systems comprising an inhibitor-doped layer-by-layer (LBL) clay-polyelectrolyte overcoated with a dense organically-modified silicate (Ormosil) are investigated as corrosion protectors for aluminium. As separate coatings, neither the LBL nor Ormosil films were found to provide adequate corrosion protection of the underlying metal. A combination of the two coating methods was found to produce a synergistic enhancement of corrosion resistance characteristics, as determined by using electrochemical techniques. This effect occurs due to the formation of sol-gel cross-linked LBL multilayers. Moreover, the LBL-sol-gel hybrid stratum seals the inhibitor ions into the polyelectrolyte layer, thereby producing a reservoir of corrosion inhibitors in the direct vicinity of the metal. Importantly, the LBL multilayers not affected by sol-gel promote lateral diffusion of an active corrosion inhibitor along the surface. Such a layered system can be considered as an example of performance optimisation by multilayer stratification of nanostructured materials. The combination of strong barrier functions, efficient corrosion inhibitor delivery, low cost of the components, and ecological compliance would be difficult to attain in traditional corrosion protection approaches.