Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)It is well known that Al-Si alloys, which are widely applied in the aerospace and automotive industries, can have significant improvements in mechanical properties by microstructural modifications induced by foundry operational conditions and by subsequent heat treatments. Such microstructural modifications can equally affect the resultant corrosion resistance. The aim of this study was to contribute to the understanding of the role of three different microstructural modification techniques on the general electrochemical corrosion behavior of an Al 9wt%Si alloy, i.e., (i) eutectic modification by sodium fluoride additions to the melt (ii) T4 heat-treatment consisting of a sequence of solution treatment and water-quenching and (iii) laser surface remelting (LSR) using a continuous CO, laser. After metallographic procedures and microscopy analysis, the general electrochemical corrosion resistance was evaluated by both the electrochemical impedance spectroscopy (EIS) technique and Tafel's plots carried out in a 0.5M NaCl test solution at 25 degrees C. An equivalent circuit has also been proposed and impedance parameters have been simulated by the Zview(R) software. It has been observed that both the LSR and the eutectic modification techniques have induced microstructural morphologies typified by highly branched fine silicon fibers and thus contributing to an increase of alpha-phase/Si surface boundaries, with a deleterious effect on the electrochemical corrosion resistance.113205212FAEPEX-UNICAMPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)