Qualitative study on the corrosion behavior of Mg-Sn-Al-Zn alloys with different Sn contents by hot extrusion

Purpose This paper aims to fill the gap in knowledge regarding how Sn content and extrusion affect the corrosion behavior of Mg-xSn-2Al-1Zn alloys in a 3.5 wt.% NaCl solution. Design/methodology/approach The corrosion resistance of Mg-xSn-2Al-1Zn alloys (x = 3, 4, 5) in 3.5 Wt.% NaCl was assessed via microstructural characterization, immersion corrosion testing and electrochemical analysis. Findings The results indicate that the 5 Wt.% Sn alloy demonstrates the smallest grain size of 5 µm, with Mg2Sn as the predominant secondary phase, which increases with Sn concentration and extrusion-induced fragmentation. In immersion tests, the homogeneous Mg-4Sn-2Al-1Zn alloy exhibited exceptional corrosion resistance (2.286 mm/y), whereas the extruded Mg-3Sn-2Al-1Zn alloy showed worse performance (13.944 mm/y). Electrochemical assessments indicated that the homogeneous Mg-4Sn-2Al-1Zn alloy exhibited the minimal corrosion current density of 1.645 × 10−5 A·cm−2, Corrosion products formed denser films on homogeneous alloys, whereas extruded alloys exhibited looser structures. Pitting and galvanic coupling dominated corrosion mechanisms. Extruded alloys exhibited diminished corrosion resistance owing to intensified galvanic effects. Originality/value This study provides valuable insights into the combined effects of Sn content and extrusion process on the corrosion behavior of Mg-Sn alloys, which is helpful for further study of Mg-Sn alloy system.