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 al loys, 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 mang anese-containing particles (such as Al23CuFe4), as well as the Al2Cu p articles. While Al2CuMg particles tended to dissolve relative to the m atrix, limited local dissolution of the matrix was also observed aroun d 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 t he matrix.