3.1. Characterizing the effects of pre-treatments
Microscopic examination was made after degreasing and pickling process to verify if these pre-treatments affect the surface topography of the specimen. By comparing micrographs Fig. 3a and b before and after degreasing process, we concluded that degreasing process did not change the surface topography of the specimens. Moreover, EDS analysis showed that the constituent particles; i.e. Al7Cu2Fe, Al2CuMg and Mg2Si were always present after the degreasing treatment. On the contrary, after the pickling solution exposure, numbers of pits were observed at the surface of the specimen. The pickling process was found to attack the constituent particles resulting in pits formations (Fig. 3c and d). During SEM examination of the pickled specimens, it was observed that some particles were completely dissolved while others were partially dissolved leaving behind a trace (Fig. 3d). This phenomenon has also been reported earlier [16]; Birbilis et al. have shown that nature of the constituent particle had an influence on the pitting process. EDS analysis of some partially dissolved particles showed that these were particles rich in Cu and Fe; i.e. Al7Cu2Fe and Al2CuMg.