Evaluation of corrosion resistance of Al-10Si-Mg alloy obtained by means of Direct Metal Laser Sintering

Direct Metal Laser Sintering (DMLS) is a powder-bed based Additive Manufacturing (AM) technique, which allows fully dense near net-shape parts to be obtained thanks to a powerful laser source able to melt and consolidate the powders layer by layer. Many types of metals are available for DMLS, and aluminium alloys play a major part in applications in different fields, from aerospace to automotive and robotics, due to their high strength-to-weight ratio. In previous years the DMLS technique has been refined with the final aim of producing complex shape components with these alloys. In this study the corrosion behaviour of an aluminium alloy processed through DMLS was studied using Potentiodynamic (PD) tests and Electrochemical Impedance Spectroscopy (EIS) tests. All the tests were executed on Al-10Si-Mg alloy in aerated diluted Harrison solution on surfaces obtained sectioning samples along different orientations with respect to the building direction. The effect of different surface finishing - shot peening and mechanical polishing - was also evaluated. The results highlighted preferential dissolution of α-Al at the border of the laser scan tracks and a slight variation with plane orientation. Moreover, the modification of the surface by shot peening or polishing increases pitting potential and reduces corrosion rate.