Corrosion of Environmentally Friendly Lanthanum Conversion Coating on AA2024-T3 Aluminum Alloy

摘要

In this work, lanthanum conversion coating applied on AA2024-T3 aluminum alloy. The coatings were analyzed by optical and scanning electron microscope. The composition and phase structure of the coating were evaluated by EDS and XRD, respectively. Corrosion properties of the coating were investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. To explain the corrosion behavior of the coating, equivalent circuit was developed from the measurements. Results showed that the coating has a nanocrystaline structure with crystal size less than 50 nm which is composed of La_2O_3. Additionally, EIS measurements showed that the lanthanum conversion coating was monolayer. Measurements taken by polarization tests showed that the coating increased corrosion potential and decreased corrosion current density approximately one order of magnitude.