On the Zr Electrochemical Conversion of Additively Manufactured AlSi10Mg: The Role of the Microstructure

Abstract

Additively manufactured (AM) AlSi10Mg is one of the most studied AM aluminium alloys to date. While several studies have focused on investigating its mechanical properties and corrosion performance, very little work has been dedicated to study corrosion protection mechanisms and surface treatments applicable for this material. This work presents for the first time an analysis of the mechanism of Zr electrochemical conversion on AM AlSi10Mg parts. A comparison with the conventional cast alloy was also conducted. An analysis of the specimens using SEM/EDS provided interesting insights concerning the effect of the microstructure on the deposition of the Zr conversion layer. This work demonstrates that due to the very fine microstructure and distribution of alloying elements in AM AlSi10Mg, a homogeneous deposition of the Zr conversion layer is promoted. Conversely, the cast alloy is characterized by a very heterogeneous deposition of the Zr conversion layer due to the presence of relatively large Fe-containing intermetallic particles. The influence of the conversion coating on the corrosion performance of these materials was also studied. The results show that while the conversion treatment has no impact on the corrosion resistance of the cast alloy, it greatly improves the passivity of the AM AlSi10Mg samples.