Characterization and electrochemical corrosion properties of Sn and Al+Sn containing coatings on magnesium alloys prepared by laser surface treatment

摘要

Sn and Al+Sn containing coatings were prepared on the surface of AZ91D magnesium alloy by laser surface treatment. The microstructure and composition of specimens were analyzed by metallurgical microscope, scanning electron microscope (SEM), field emission scanning electron microscope (FESEM) equipped with energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The corrosion resistance of the as-received and laser treated magnesium alloys were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests. The effect of Sn and Al+Sn addition on the microstructure, composition and corrosion behavior of magnesium alloys was investigated. Results showed that the surface presents different phase composition. The corrosion resistance of magnesium alloys sharply decreased after laser surface cladding (LSC) of Al+Sn, for the galvanic corrosion between Al and Sn. Conversely, the corrosion resistance was improved by laser surface alloying (LSA) of Sn due to the refinement effect and the protection of Mg_2Sn and SnO_2 in the grain boundary to the a-Mg matrix.