In this work a scanning electrochemical microscopy (SECM) study of electrochemical activity for intermetallics in the Al-1.78%Si- 13.4%Mg alloy was carried out. For the experiments, a 0.1M NaCl solution with hidroxymethlyferrocene as a mediator and a Pt scanning probe 25 µm in diameter were used. SECM images obtained while the sample was held at open circuit conditions were compared to optical photomicrographs in the same area. The electrochemical activity of the intermetallics Mg2Si and Al3Fe is discussed.