Studio della resistenza alla corrosione della lega AlSi10Mg ottenuta per Additive Manufacturing in soluzione di cloruri

The production of components by means of additive manufacturing (AM) technology modifies the materials properties, giving them particular microstructures. In the present work, the corrosion resistance in chloride solutions of a AlSi10Mg alloy obtained by “Direct Metal Laser Sintering” (DMLS) process was evaluated. The alloy was studied by means of anodic potentiodynamic tests considering two superficial conditions: with the rough surface as produced by the DMLS technology or after mechanical polishing and passivation in air. The results show the effect of the surface conditions deriving from the production process and the microstructure. A worsening of the resistance to the localized corrosion was observed for the alloy in the “as produced” conditions, with decrease of the pitting potential and increment of passive current density compared to the polished and air passivated surface. The difference in the behavior becomes negligible with the increase of chlorides concentration. The initiation of corrosion takes place by the selective dissolution of the α-Al phase at the edge of the melting pool, stimulated by nobler precipitates, especially silicon based. A main role of chloride concentration in the initiation of localized corrosion was confirmed, whereas the pH solution doesn’t seem to produce relevant effects in the interval considered for testing.