A review of the electrochemical and galvanic corrosion behavior of important intermetallic compounds in the context of aluminum alloys

Aluminum alloys are widely sought for different applications due to their high strength-to-weight ratio. Most often this increased strength of the alloy is achieved by specific alloying elements and heat treatment processes which give rise to second phases intermetallic particles (IMPs) also known as intermetallic compounds (IMCs). These second phases play a dominant role in the corrosion susceptibility of aluminum alloys. This review provides a systematic survey of the electrochemical, and galvanic corrosion behavior of IMPs in the context of aluminum alloys. A discussion of the electrochemical/galvanic corrosion behavior of selected/important intermetallic compounds that are commonly found in aluminum alloys such as the Q-phase (Al4Cu2Mg7Si8), pi-phase (Al8Mg3FeSi6), theta-phase (Al2Cu), S-phase (Al2CuMg), the beta-phase (Mg2Si), beta-phase (Al3Mg2), delta (Al3Li), eta-phase (MgZn2), and beta-phase (Al3Fe) is provided. In addition, the limitations in the electrochemical characterization of intermetallic compounds, the research gap, and prospects are also provided in addition to the phenomenon of galvanic polarity reversal and self-dissolution of IMPs. Schematic of the galvanic corrosion evolution on eta-phase (MgZn2), beta-phase (Al3Mg2), Q-phase (Al4Cu2Mg8Si7), and pi-phase (Al8Mg3FeSi6) coupled to aluminum at different pH values using the SVET current density map.