Corrosion behavior and oxide layer of selective-laser-melted Al-Mg-Sc-Zr alloy in marine atmospheric environment with different Cl−concentration

Abstract

In this study, the corrosion response of the Al-Mg-Sc-Zr alloy produced by selective laser-melting in marine atmospheric environments with different Cl⁻ concentrations was studied by electrochemical and immersion. Microstructural observations showed the microstructural of Al-Mg- Sc -Zr alloy featured a double grain microstructure, making up a coarse and fine grain area. TEM showed that some white precipitates enriched with Zr and Sc were dispersed in the samples. The potentiodynamic polarization test indicated increasing the Cl⁻ concentration led to a negative shift of corrosion potential and narrowed the potential range of the passive zone, which also caused the increase of corrosion current density value. The electrochemical impedance spectroscopy showed that higher Cl⁻ concentration was greatly detrimental to generating a compact and dense oxide film on the Al-Mg-Sc-Zr alloys, as indicated by decreasing the resistance of the corrosion product layer and charge transfer resistance. The immersion test demonstrated that the samples suffered serious pit corrosion when the Cl⁻ content increased to 1.5 and 3.5 wt%, showing a larger size and more depth of corrosion pits. This study is expected to provide data to determine the reliability of the SLM-manufactured Al-Mg-Sc-Zr alloy in marine atmospheric conditions.