Influence of an anodized layer on the adhesion and surface protective performance of organic coatings on AA2024 aerospace Al alloy

In the present work, the effect of the anodized surface on the adhesion and corrosion protection behavior of epoxy coatings was evaluated on AA2024 alloy. Surface characterization involving the use of scanning electron microscopy (SEM), optical profilometry, and X-ray diffraction (XRD) analysis was conducted to evaluate the anodized layer of Al alloy samples and how it influences the coating. The surface wettability was also assessed using water contact measurements. Electrochemical corrosion analysis of the coated samples in a 3.5% NaCl solution was performed using continuous monitoring of the open circuit potential, followed by electrochemical impedance spectroscopy tests for up to 30 days. Scratch resistance analysis was performed to quantitatively appraise the adhesion strength of the epoxy coatings on the anodized AA2024 samples. The scratch resistance analysis results indicated the adhesion strength was improved when the AA2024 samples underwent anodization treatment. It was concluded that the anodized layer improves the adhesion between the organic coatings and base substrate, which consequently enhanced the surface protection performance against corrosion in 3.5% NaCl solution.