Smart Coating Embedded with pH-Responsive Nanocapsules Containing a Corrosion Inhibiting Agent

Triethanolamine (TEA), an amine-based corrosion inhibitor, was encapsulated and then embedded into an epoxy coating to provide long-term corrosion protection of aluminum alloy 3003. TEA was encapsulated by means of free-radical polymerization, yielding an average particle size of 450 nm. An applied epoxy coating containing 10 wt % of the nanocapsules successfully protected an artificially defective area for a long period due to TEA adsorption, which resulted in the formation of an inhibiting layer. Electrochemical impedance spectroscopy showed an inhibition efficiency surpassing 85% when the metal experienced mild corrosion in its early stages, and the inhibiting layer started to form by local pH level change, which triggered the release of TEA. On the basis of the results of a scanning vibrating electrode technique, the current density of the metal surface in the presence of an encapsulated TEA coating was significantly lower than that of the control coating with no nanocapsules. Optical microscope and s...