Effect of the addition of thermally activated hydrotalcite on the protective features of sol–gel coatings applied on AA2024 aluminium alloys

The present work assesses the effect of the thermal activation of hydrotalcite particles when they are added to a hybrid sol–gel film to improve its corrosion properties. Although previous studies have demonstrated the anti-corrosion properties of as-synthesised hydrotalcite particles incorporated into sol–gel coatings, their inhibitive action has not been well-established. Some hypotheses suggest that it should be related to their anion exchange capacity, which increases when the hydrotalcite is thermally activated.Several techniques were used to characterise the uncalcined and calcined hydrotalcite: X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric and differential scanning calorimetry techniques. To analyse the inhibition action, hybrid sol–gel coatings were doped with 10 wt% of CHT. Accelerated tests and electrochemical impedance spectroscopy were used for performance evaluation between the sol–gel coatings doped with calcined and uncalcined HT.The results obtained indicate the superior behaviour of samples doped with calcined HT at longer immersion times, which suggests better inhibition action.