Optimal current density for cathodic CeCC deposition on anodized AA2024-T3 aircraft alloy

• Published in: Journal of applied electrochemistry Vol. 54; no. 12; pp. 2887 - 2918
• Main Authors: Kozhukharov, Stephan, Girginov, Christian, Portolesi, Stefania, Tsanev, Aleksandar, Lilova, Vanya, Petkov, Plamen
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.12.2024; Springer Nature B.V
• Subjects: Aircraft; Aluminum; Aluminum base alloys; Aluminum oxide; Anodic protection; Cathodic protection; Cerium; Chemistry; Chemistry and Materials Science; Contact angle; Conversion coatings; Corrosion prevention; Corrosion tests; Current density; Deposition; Electrochemical corrosion; Electrochemical impedance spectroscopy; Electrochemistry; Energy distribution; Industrial Chemistry/Chemical Engineering; Photoelectrons; Physical Chemistry; Primers (coatings); Research Article; Spectrum analysis; Surface properties; X ray photoelectron spectroscopy; AA2024-T3 aircraft alloy; Cerium conversion coatings (CeCC) electrodeposition currents; Anodic aluminum oxide (AAO); Surface characteristics; EIS; PDS
• ISSN: 0021-891X; 1572-8838
• DOI: 10.1007/s10800-024-02143-7

The reliable and durable corrosion protection of structural materials, such as the AA2024-T3 aircraft alloy, is the subject of intensive research worldwide. This alloy, highly doped in its composition, inherently exhibits increased susceptibility to electrochemical corrosion compared to pure aluminum. Among the most promising and environmentally friendly primers are Anodic Aluminum Oxide (AAO) and Cerium Conversion Coatings (CeCC). Consequently, the combined AAO/CeCC coating primers are anticipated to offer superior protective properties. However, the optimal approach and conditions for CeCC formation on the AAO layer remain uncertain. This study presents a comparative characterization of cathodically deposited CeCC on pre-formed AAO on the AA2024-T3 alloy, revealing the opportunity for electrochemical CeCC formation and potential detrimental effects. The CeCC depositions were conducted at current densities ranging from 0 to 25 mA cm −2 . The analysis included the following: (1) color characterization and contact angle measurements, (2) surface observations using optical metallographic, atomic force, and scanning electron microscopy, (3) element distribution using energy dispersion X-ray and X-ray photoelectron spectroscopy, and (4) corrosion tests. These involved electrochemical impedance spectroscopy (EIS) and potentiodynamic scanning after 24, 168, 336, 504, and 672 h of exposure to a 3.5% NaCl model corrosive medium. The result analysis has revealed that the most favorable current densities for CeCC deposition on the surface of anodized AA2024-T3 alloy fall within the range of 0 to 5 mA cm −2 . Higher values adversely affect the surface properties of the specimens. These findings were corroborated by all the analytical techniques employed. Graphical abstract