presents the results of topography measurements taken for specimen that has undergone the pickling treatment. Here we can observe that most of the pits have depth below 8 μm with very few exceeding this value. The possible reason for this phenomenon, as observed by SEM, that some particles were partially dissolved leaving behind the remnants. In their work for aluminium alloys, Ezuber et al. [17] have shown that pit morphology depends on the type of constituent particles present and their reactivity with the exposed solution.