Fretting tests on pre-stressed specimen have been performed on the treated and non-treated Al-Cu 2024 and Al-Zn 7075 aluminium alloys. Chromic acid anodizing (CAA) pre-treatment was applied to the contact surface. The oxide layer depth was about 2 mu m. The imposed amplitude D ranged from +/-10 to +/-75 mu m and normal load F-n from 500 to 1000 N. The static external load sigma(s) was set at sigma(D) (sigma(D), fatigue limit). The tests were carried out with a frequency of 1 or 5 Hz up to 10(6) cycles. Variations of the tangential force vs. displacement amplitude have been recorded for each cycle. Friction coefficient and oxide layer degradation were studied at the different experimental conditions. Cracking induced by fretting and particularly crack nucleation were emphasized.