Electrochemical behavior of approximant phases in the Al–(Cu)–Fe–Cr system

The corrosion behavior of quasicrystalline approximant phases in the Al–Cu–Fe–Cr and Al–Cr–Fe systems is studied and compared with stainless steel. The electrochemical solution contains citric acid and chloride anions. Electrochemical behavior is investigated by measuring the open-circuit potential, by calculating the polarization resistance and by recording anodic polarization curves. The electrolytic solutions are analyzed after electrochemical experiments and the samples are characterized by scanning electron microscopy and transmission electron microscopy. Two corrosion processes occur under electrochemical stress: general corrosion and pitting corrosion. The resistance to both general and pitting corrosion under these aggressive conditions seems to be mainly influenced by the chemical composition of the samples. Clearly, Cr enhances corrosion resistance whereas Cu has a negative influence. General corrosion affects the surface chemical composition due to preferential dissolution of aluminum and to the increase of oxygen content. Some of the samples in the Al–Cr–Fe system have electrochemical properties that can be compared favorably with properties of stainless steel.