A method has been developed to characterize the passivation film formed on aluminum in marine atmosphere, whether polluted or not by sulphur oxides and fluorides.The information thus obtained was integrated by X-ray diffractometric analyses.The following corrosion products were found in the marine atmosphere: A1203 + 3Hz0 + A1 (oxychoride) + A1 (hydroxide) (The latter two compounds had not been revealed by X-ray analysis).The corrosion products found in the polluted atmosphere were: AIFG Az(so4)3 . H W , ; AIII(OH)~OC~G AlFl Y~(OH)I 4; 16Al(OH,F)3 6H10; AIF,,6,(OH)l35 . HzO.