Application of Commercial Surface Pretreatments on the Formation of Cerium Conversion Coating (CeCC) over High-Strength Aluminum Alloys 2024-T3 and 7075-T6

The selection of appropriate surface pretreatments is one the pending issues for industrial application cerium-based chemical conversion coatings (CeCC) as an alternative toxic chromate coating (CrCC). A two-step pretreatment based on commercial products has been successfully used here to obtain CeCC AA2024-T3 and AA7075-T6. Specimens processed 1 15 min in solutions containing CeCl3 H2O2 have studied by scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), glow discharge optical emission spectroscopy (GDOES), potentiodynamic linear polarization (LP), electrochemical impedance (EIS), neutral salt spray (NSS) tests. SEM-EDX showed that was firstly observed deposits, followed a general coverage formation cracks where getting thicker. GDOES confirmed increase thickness deposition proceed, over 7075 being faster than 2024. There Ce-rich layer both alloys aluminum oxide/hydroxide between upper matrix. According LP EIS, all samples offered cathodic protection comparable degradation chloride-containing media. Finally, NSS test corroborated anti-corrosion properties obtained after employed.