The Relation between the Microstructure and Corrosion Behavior of Aluminum Alloy AA2024-T3

摘要

Two different acidic pretreatments were applied on aluminum alloy 2024-T3 before the trivalent chrome process (TCP). Micro-sized pits were observed on the alloy surface treated with Deoxidizer 6, which contained chromic acid and hydrofluoric acid, while the surface morphology hardly changed after nitric acid pretreatment. Moreover, a thin film containing Cr was formed on the surface after Deoxidizer 6 pretreatment. This passivation film deteriorated the reactivity during TCP. The TCP coating treated after nitric acid was thus thicker than that treated after Deoxidizer 6. The effect of immersion time of acidic pretreatment was examined using potentiodynamic polarization curve. It was found that increasing immersion time was not necessarily proportional to the anti-corrosion properties of TCP coatings.