Al-Si hypereutectic alloys produced by spray forming represent an important
technological development for application in the aeronautical and automotive industries. Due to
some special properties these alloys find application as cylinder liners, mainly due to their high
strength and wear resistance. Much research has been carried out to evaluate the mechanical
properties of these alloys but the literature on their corrosion performance is still very scarce. In this
study, the corrosion behaviour of a spray formed Al-Si-Cu hypereutectic alloy was investigated by
electrochemical impedance spectroscopy (EIS) in acid (pH 3.3), neutral (pH 7) and alkaline (pH 11)
solutions. Intense localized attack occurred in the acid electrolyte and the impedance decreased with
time of immersion. In the neutral medium, the alloy was passivated but localized attack also
occurred on weak areas of the passive film. In the alkaline medium, precipitation of corrosion
products occurred during the first hours of immersion causing the increase of impedance but
thickening of this layer led to cracks growth with time and, consequently, to the exposure of
metallic substrate, resulting in the decrease in impedance for longer periods.