Zn-Al layered double hydroxides as chloride nanotraps in active protective coatings

Zn-Al layered double hydroxides (LDHs) intercalated with nitrate anions are suggested as chloride nanotraps for organic polymeric coatings. The addition of such nanotraps to a polymer layer drastically reduces the permeability of corrosive chloride anions through the protective coatings. In solution, Zn(2)-Al-NO3 LDHs are responsive to the concentration of chlorides and the release of nitrates is accompanied by entrapment of chlorides, with the process governed by ion-exchange equilibrium. In particular, a coating modified with LDH-NO3 was found to exhibit significantly lower permeability to chlorides when compared to both unmodified and LDH-Cl-containing coatings, which proves the applicability of LDHs in delaying coating degradation and corrosion initiation. (C) 2011 Elsevier Ltd. All rights reserved.