Self healing ability of inhibitor-containing nanocapsules loaded in epoxy coatings applied on aluminium 5083 and galvanneal substrates

• pH sensitive nanocapsules loaded with corrosion inhibitor were prepared.
• Epoxy coatings loaded with the smart nanocapsules were applied on AA5083 and steel.
• The self healing ability was proved by LEIS and SVET.
• Long term corrosion protection was observed in standard corrosion tests.

The self-healing ability of water based epoxy coatings modified with nanocapsules loaded with 2-Mercaptobenzothiazole (MBT) and applied on AA5083 and galvanneal substrates was investigated by electrochemical techniques and salt spray corrosion tests.The electrochemical impedance results show that the presence of nanocapsules does not affect the barrier properties of the coatings and evidence a decrease of the corrosion activity in the presence of inhibitor-loaded nanocapsules. Localised electrochemical impedance spectroscopy (LEIS) and the scanning vibrating electrode technique (SVET) revealed that the corrosion process over artificial defects exposed to NaCl electrolytes was healed in the presence of the nanocapsules loaded with corrosion inhibitor. The coated galvanneal samples show corrosion attack when exposed to the salt spray test, but the AA5083 samples did not show signs of corrosion activity over 1000 h of exposure. All the as prepared samples revealed good adhesion behaviour. However, after immersion delamination across defects was more intense for the galvanneal samples. The results highlight that addition of nanocapsules in water based epoxy coatings is a promising strategy towards the development of self-healing water based epoxy coatings.