Hydrophobic surface treatments for improving the corrosion resistance of anodized AA2024-T3 alloys

Abstract

The present study investigates the use of hydrophobic sealing treatments to improve the corrosion resistance of anodized aluminium alloys. Alternative hydrophobic processes to the hydrothermal sealing were tested. One is based on a monocarboxylic acid, myristic acid, and others involve the deposition of hybrid sol-gel film. The samples characterization was performed by Field Emission Scanning Microscopy. The hydrophobic properties were assessed by contact angle measurements, and Electrochemical Impedance Spectroscopy was used to study the anticorrosive properties. All the hydrophobic treatments improved the corrosion resistance of the anodized samples with respect to the hydrothermal treatment. The best results were obtained using the hybrid sol-gel film, where high impedance values are measured after long immersion periods in a 0.1 M NaCl solution. Especially good behaviour was observed in samples sealed with the sol-gel film when the sol was previously heated at 70 °C. This temperature was necessary to dissolve the aggregates that formed at room temperature, which contribute to a more efficient sealing.