Electrochemical corrosion behavior of Al-Si alloy composites reinforced with in situ TiB2 particulate

Understanding the corrosion behavior of TiB2p-reinforced aluminum matrix composites is crucial for their development as effective composites. In this work, corrosion characteristics of in situ TiB2 particulate reinforced Al-Si alloy (A356) composite after T6 treatment are investigated by electrochemical techniques. The electrochemical impedance spectroscopy (EIS) reveals that the protection of nature film for the composites is worse than that for A356 alloy. Polarization experiments testify that the composites are susceptible to corrosion compared with their matrix alloys. Moreover, the corrosion resistance of the composites markedly decreases with increase in the TiB2 content. The observations of the corrosion morphologies after polarization test show that the corrosion primarily occurs at the interdendritic sites with a large amount of TiB2 particulates. Corrosion progress continues into the composite inner along the regions of alpha-Al dendrite. The poor corrosion resistant properties of the composites are considered primarily due to the galvanic corrosion between noble TiB2 reinforcements and more active aluminum matrix, as well as the weak protection of the defective nature film on the composite.