Effects of strontium addition on the microstructure and corrosion behavior of A356 aluminum alloy

Highlights: • Unmodified A356 has the lowest corrosion resistance compare to Sr modified. • Corrosion resistance do not change significantly by dendrite grain size. • In die cast, 120 ppm Sr modified A356 have the highest corrosion resistance. • In sand cast, 170 ppm Sr modified A356 have the highest corrosion resistance. 3XX series Al–Si alloys are generally used in corrosive environments open for oxidation such as rainwater and seawater. The dendrite size and characteristics of the eutectic Si are important factors determining the properties of A356 alloy. In this study, the microstructure of Sr modified A356 aluminum alloy and the changes in corrosion properties were investigated. The alloy was cast into die and sand molds to examine the effect of cooling parameters on the microstructure. Sr modification was carried out by adding four different weight percentages (0, 120, 170 and 250 ppm). Corrosion behavior of the produced alloys was investigated by two ways. One of them was electrochemical impedance spectroscopy technique and the other is potentiodynamic polarization plots that was carried out in 3.5 wt.% NaCl solution at 25 °C. The corrosion resistance of the alloy was found to be increasing as Sr content was increased which modified the morphology of the silicon in the alloy.