Role of second phase particles in pitting corrosion of 3003 Al alloy in NaCl solution

The second phase particles in 3003 aluminum (Al) alloy were characterized by scanning electron microscope, energy‐dispersive X‐ray analysis and X‐ray diffraction techniques. The role of second phase particles in Al alloy pitting corrosion was investigated by cyclic polarization measurement, and scanning vibrating electrode technique. Results demonstrated that the second phase particles in 3003 Al alloy are mainly Al_x(Fe,Mn) intermetallics, with an average diameter of about 5 µm. The enrichment of Mn in second phase particles forms a galvanic cell effect relative to the adjacent Al alloy substrate. The initiation of pitting corrosion of 3003 Al alloy is the local dissolution of Al substrate around the second phase particles. When a sufficient amount of Al is dissolved away, the second phase particles drop off from the Al substrate, forming large pitting cavities that are usually linked each other.