3.2. SEM observations of anodic coating
It is of scientific interest to study the effect of these pre-existing defects formed on the specimen surface during pretreatment solution exposure prior to the anodizing step. In Fig. 5, surface observations made by SEM are shown for specimens undergone the anodization process. It can be clearly seen that anodization tend to form a smooth anodic coating with few pits still present at the surface (Fig. 5). These pits can act as stress raiser during fatigue loading and can significantly affect the fatigue life by reducing or even eliminating the initiation period. On the contrary to pickled specimens, no traces of partially dissolved particles were found for specimens that undergone complete anodization process. This phenomenon can be explained by the complete dissolution of remnant particles, left after pickling solution exposure, during anodizing process.