The local corrosion behavior of additive manufactured AlSiMg specimens was studied using the SEM and SKPFM techniques. A morphological characterization of corroded areas revealed that crystallographic pitting developed in the aluminium grains inside the melt pool borders, from where corrosion spread to adjacent zones. The local Volta potential analysis showed that there is a close relation between the cellular grain size and the potential difference between the silicon and the aluminium phase. SKPFM measurements explained why the melt pool borders were more severely attacked by corrosion than other regions in the surface of the AM specimens. In regions with larger and coarser microstructures, greater potential difference between the phases was found, which represents a higher driving force for galvanic corrosion.