Conversion coating growth on 2024-T3 Al alloy. The effect of pre-treatments

• Published in: Surface & coatings technology Vol. 202; no. 14; pp. 3396 - 3402
• Main Authors: Rangel, C.M., Paiva, T.I., da Luz, P.P
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.04.2008; Elsevier
• Subjects: 2024 aluminium alloy; Applied sciences; Benzotriazole; Cerium salts; Conversion coatings; Corrosion; Corrosion prevention; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals. Metallurgy; Physics; Pre-treatments; Production techniques; Surface treatment; Surface treatments; 2024 aluminium alloy; Pre-treatments; Cerium salts; Conversion coatings; Benzotriazole; Aluminium base alloys; Conversion coating; Cerium; Surface treatments; Corrosion protection; Coatings; Corrosion inhibitors; Rare earths; Pretreatment
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2007.12.017

The cleaning pre-treatments, generally based on alkaline etching and acid pickling, provide a surface standard condition before the application of conversion coatings. In this work, the effect of cleaning pre-treatments on the surface morphology and activity of 2024-T3 Al alloy and on chromium-free Ce-based conversion coatings formation has been studied. Variations in the open circuit potential of the alloy of ~ 1.5 V were registered during the cleaning pre-treatment, accounting for the complex electrochemical phenomena involved. Even though, the presence and concentration of additives such as H 2O 2 was found to be essential to a fast kinetics coating formation, effective cleaning pre-treatments are demonstrated to be associated to the production of grained well structured coatings, allowing necessary redox reactions for conversion coating formation. The effect of copper-rich areas and its effect on the conversion coating growth rate and morphology were also studied using benzotriazole additions at different stages in the cleaning pre-treatments.