Metal additive manufacturing (MAM), also known as metal 3D printing, is a rapidly growing industry based on the fabrication of complex metal parts with improved functionalities. During MAM, metal parts are produced in a layer by layer fashion using 3D computer-aided design models. The advantages of using this technology include the reduction of materials waste, high efficiency for small production runs, near net shape manufacturing, ease of change or revision of versions of a product, support of lattice structures, and rapid prototyping. Numerous metals and alloys can nowadays be processed by additive manufacturing techniques. Among them, Al-based alloys are of great interest in the automotive and aeronautic industry due to their relatively high strength and stiffness to weight ratio, good wear and corrosion resistance, and recycling potential. The special conditions associated with the MAM processes are known to produce in these materials a fine microstructure with unique directional growth features far from equilibrium. This distinctive microstructure, together with other special features and microstructural defects originating from the additive manufacturing process, is known to greatly influence the corrosion behaviour of these materials. Several works have already been conducted in this direction. However, several issues concerning the corrosion and corrosion protection of these materials are still not well understood. This work reviews the main studies to date investigating the corrosion aspects of additively manufactured aluminium alloys. It also provides a summary and outlook of relevant directions to be explored in future research.

This work evaluates the corrosion resistance of three Al-Si alloys processed by additive manufacturing (Al-Si7-Mg, Al-Si10-Mg, and Al-Si12) through a comparative analysis. It explores the influence of the silicon content on the microstructure and corrosion behavior of these alloys. An initial scanning electron microscopy analysis revealed that the silicon content in the samples affected the level of connectivity of the Si network, and this, consequently, influenced the formation of micro-cracks during corrosion. A model describing the evolution of the corrosion attacks and micro-cracks formation in the AM Al-Si alloys is proposed here.

In this work, the role of the Si phase microstructure in the anodizing behavior of Al-Si alloys is studied. Experiments were conducted using an additive manufactured (AM) Al-Si10-Mg specimen and a cast alloy of approximately the same chemical composition. A systematic characterization of the anodic oxide film was conducted using a variety of surface analysis techniques. Clear evidence is provided through X-ray photoelectron spectroscopy analysis for the almost entire oxidation of Si during the anodizing of the additive manufactured specimens, which can explain the lower anodizing efficiency observed in the AM material compared to the cast alloy. Additionally, a more detailed characterization of the oxide layer revealed that a slightly thinner anodic oxide film is formed at the borders of the characteristic melting tracks resulting from the metal additive manufacturing process. Furthermore, the features observed in the voltage–time response during the anodizing of the AM specimens seem to be closely associated with the dimensions of the Al/Si cells present in the plane parallel to the direction of the oxide front growth.

This work focuses on the effect of dissolved oxygen concentration in liquid lead-bismuth eutectic (LBE) on the onset of dissolution corrosion in a solution-annealed 316 L austenitic stainless steel. Specimens made of the same 316 L stainless steel heat were exposed for 1000 h at 450 °C to static liquid LBE with controlled concentrations of dissolved oxygen, i.e., 10−5, 10−6, and 10−7 mass%. The corroded 316 L steel specimens were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). A complete absence of dissolution corrosion was observed in the steel specimens exposed to liquid LBE with 10−5 and 10−6 mass% oxygen. In the same specimens, isolated “islands” of FeCr-containing oxides were also detected, indicating the localized onset of oxidation corrosion under these exposure conditions. On the other hand, dissolution corrosion with a maximum depth of 59 μm was detected in the steel specimen exposed to liquid LBE with 10−7 mass% oxygen. This suggests that the threshold oxygen concentration associated with the onset of dissolution corrosion in this 316 L steel heat lies between 10−6 and 10−7 mass% oxygen for the specific exposure conditions (i.e., 1000 h, 450 °C, static liquid LBE).

This work analyzes the galvanostatic anodizing behavior of additive manufactured (AM) Al-Si alloys. Two main factors were studied here: 1) the influence of Si content on the anodizing behavior and on the porous structure of the anodic oxide film, and 2) the effect of pre-existing internal pores on the anodizing behavior of these materials. Three different alloys were anodized in H₂SO₄ electrolyte, with 7%, 10%, and 12% Si. The voltage responses of the different samples during anodizing were compared and the formed oxide was analyzed. The amount of Si in the AM Al-Si alloys was found to have a great influence on the anodizing voltage and consequently on the porous structure of the anodic oxide layer. However, the anodic oxide growth rate was nearly independent of the Si content in the samples. Moreover, the effect of internal porosity resulting from the metal additive manufacturing process on the anodizing behavior of these specimens was also analyzed. An outer anodic oxide layer decorated the pre-existing internal pores that were reached by the anodic oxide front. These internal pores were also characterized by the systematic appearance of cracks resulting from the volume expansion of anodic oxide layers advancing in opposite directions.