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The use of smart nanocontainers to store corrosion inhibitors in coatings significantly increases the efficiency and durability of the coating, providing active corrosion protection.Here we report the synthesis of a zinc-layered hydroxide salt (LHS) and its use as a novel nanocontainer for this purpose, storing the corrosion inhibitor molybdate in the interlayer region of the LHS. Layered zinc hydroxide molybdate (ZHM) was obtained by anion-exchange reactions using layered zinc hydroxide acetate (ZHA) as a precursor, obtained by alkaline coprecipitation. The release behavior of molybdate from the ZHM nanocontainers in aqueous NaCl solution (0.05 mol/L) was evaluated using UV− vis absorption spectroscopy. The molybdate release from the ZHM nanocontainers was realized by the anion-exchange mechanism, where chloride anions replaced intercalated molybdate anions. The release was fast in the first minutes of exposure, followed by a controlled release afterward, reaching about 35% of cumulative amount of released molybdate after 30 days of exposure. The anticorrosion effect provided by the ZHM nanocontainers for carbon steel was investigated by electrochemical impedance spectroscopy. The steel substrate was coated with an epoxy resin loaded with ZHM nanocontainers (5 wt %) and immersed in an NaCl solution (0.05 mol/L) to evaluate the active mechanisms of inhibition and the anticorrosion properties of the loaded coating in comparison with a neat coating (blank). The coating loaded with ZHM nanocontainers presented the best corrosion protection performance, exhibiting an increase of R C (coating resistance) with the immersion time and superior R P (polarization resistance) for all the measured periods, compared to the blank. This effect is a consequence of the double mechanism of protection provided by the ZHM nanocontainers: (i) stimulus-response release of molybdate and its active inhibition in the scratched region by the formation of an insoluble protective film, simultaneously with (ii) removal of the corrosive chloride species from the medium.

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Benzotriazole (BTA) release from a layered double hydroxide based on Zn and Al (LDH-ZnAl/BTA) in a saline solution was investigated using UV-Vis spectroscopy, and corrosion protection was studied by OCP and EIS measurements on carbon steel samples immersed in 3.5 wt-% NaCl solution. The corrosion protection of this ion-exchanger material performance for longer periods was evaluated using a carbon steel substrate coated with a commercial epoxy primer loaded with LDH-BTA (5.0 wt-%). EIS and salt spray tests demonstrated that the LDH-BTA additive enhanced the performance of the commercial primer due to the double inhibitive effect, which is a combination of the entrapment of chloride anions simultaneously with the on-demand release of the corrosion inhibitor BTA.