A transmission electron microscopy study of constituent-particle-induced corrosion in 7075-T6 and 2024-T3 aluminum alloys

To better understand particle-induced pitting corrosion in aluminum alloys, thin foil specimens of 7075-T6 and 2024-T3 aluminum alloys, with identified constituent particles, were immersed in aerated 0.5M NaCl solution and then examined by transmission electron microscopy (TEM). The results clearly showed matrix dissolution around the iron- and manganese-containing particles (such as Al23CuFe4), as well as the Al2Cu particles. While Al2CuMg particles tended to dissolve relative to the matrix, limited local dissolution of the matrix was also observed around these particles. These results are consistent with scanning electron microscopy (SEM) observations of pitting corrosion and are discussed in terms of the electrochemical characteristics of the particles and the matrix.