Investigation of time-dependent corrosion behavior of Sr-modified AlSi12 alloy

Abstract

The effect of Sr addition on the microstructure and time-dependent corrosion properties of the AlSi12 eutectic alloy was investigated. The modified alloy contained 90 +/- 3 ppm Sr. The microstructural differences in the eutectic structure of AlSi12 alloys were assessed in terms of the Si particle size and alpha-Al volume fraction. The unmodified and Sr-modified alloys were immersed for 1, 24, 72 and 120 h in 3.5 wt.% NaCl. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were performed to analyze the corrosion characteristics of the alloys. Sr addition led to a decrease in the Si particle size, and the formation of long dendritic alpha-Al. It was found that the presence of Sr resulted in more stable corrosion behavior up to 24 h. The deterioration of the corrosion behavior of Sr-modified alloy was observed with the further increase of immersion time.