Abstract
It is well known that elements such as Fe and Si are always contained in an industrial pure aluminum. Some of them dissolve in matrix, others form Al–Fe type or Al–Fe–Si type of the intermetallic compounds. The ratio of Fe/Si in intermetallic compound particles is responsible for the pitting attacks of the aluminum. The degree of the pitting attacks attributes to the preferential dissolution of aluminum and iron in the particles. In this case, the aluminum of the intermetallic compounds is always preferentially dissolved. Then the atmosphere of a particle is changed into low pH by the hydoration of aluminum ions. The higher ratio of Fe/Si is the easier preferential dissolution of iron. The polarization measurements explained that the aluminum and ferrous ions produced by the dissolution make the oxide film around the particle weak and provide a suitable concave for developing the pitting attacks by dissoluting the matrix.
