Influence of Silicon on Intergranular Corrosion for Aluminum Alloys

In an effort to improve the tensile strength of aluminum-silicon (Al-Si) alloys used in heat exchangers, we investigated the influence of Si concentration and heat-treatment at 453K on the susceptibility of Al-Si alloys to intergranular corrosion. It was found that the susceptibility to intergranular corrosion increased with an increase in Si concentration. It also initially increased with heat-treatment at 453 K, but then decreased with long-term heat-treatment at 453 K. The addition of Mg and Mn, which affect the precipitation of Si, promoted precipitation and reduced the susceptibility of the Al-Si alloys to intergranular corrosion. With longer heat-treatment at 453 K, large Si precipitates were observed in the grains and at the grain boundaries, which reduced the susceptibility to intergranular corrosion. Short-term heat-treatment at 453K formed a continuous Si-depleted layer along the grain boundaries, which increased the susceptibility to intergranular corrosion. It is suggested that the susceptibility to intergranular corrosion was dependent on the addition of Mg and Mn. © 2013 The Japan Institute of Metals and Materials.