Influence of Iron-Silicon Ratio in Intermetallic Compound on Pitting Behavior of Aluminum

다국어 초록 (Multilingual Abstract)

Iron and silicon elements are always observed in commercially pure aluminum. Some of them dissolve in aluminum matrix as solid solution, and others form the Al-Fe or Al-Fe-Si intermetallic compounds. The ratio of Fe/Si in the intermetallic compound phases is responsible for pitting attack behavior of the aluminum. In 1.0M NaCl solution not only aluminum but also iron in the intermetallic compound preferentially will dissolve. The higher Fe/Si ratio is, the easier dissolution of iron is. The preferential dissolution leads that solution surrounding the intermetallic compound particles will be changed to low pH due to the hydrolysis of aluminum and ferrous ions produced by the dissolution. The polarization measurements and metallurgical observations explain that the low pH will make the oxide film surround the particles weak or thin, and some of them provide a suitable concave for hrther propagation for the pitting attacks.