Development and characterization of sealed anodizing as a corrosion protection for AA2024-T3 in saline media

In the present investigation, a new processing route of anodized aluminum AA2024 was developed by incorporating a hydrophobic top sealant to increase the anti-corrosion properties of the substrate in saline media. Different sealant solutions (boiling water, potassium dichromate, and cerium nitrate) were used after the sealing treatment. The surface structure was characterized by water contact angle, atomic force microscopy (AFM), and scanning electron microscopy (SEM) measurements, while the composition was assessed by X-ray photoelectron spectroscopy (XPS). Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) evaluated the anticorrosive properties. The microhardness properties were assessed with Vickers testing. Each hydrophobic treatment notably improved the corrosion resistance of the AA2024; however, the cerium nitrate system obtained the best results, given that the morphology of the hydrophobic structure generated lower surface defects with high impedance values and, consequently, very low current. The microhardness properties were positively increased after the surface modification, thus, the hydrophobic sealant improved simultaneously both electrochemical and mechanical properties. The XPS identified the presence of fluorotriethoxysilane as the chemical compound responsible for the hydrophobic properties.

Automated summary

In this study, a new processing route of anodized aluminum AA2024 was developed by incorporating a hydrophobic top sealant, which improved both the electrochemical and mechanical properties of the alloy and enhanced its corrosion resistance in saline media. The cerium nitrate system obtained the best results among the different sealant solutions used.