Dry laser cleaning of anodized aluminium

Standard anodized aluminium samples with about a 20-mu m-thick oxide layer were investigated for cleaning study by means of laser pulses. The removal caused by overheated melting and mechanical stress was studied at wavelengt hs of 1064 nm and 532 nm. The samples were examined with scanning electron; and optical microscopy. We investigated the dependence of the laser cleanin g efficiency on energy densities and the number of pulses. The layer remova l mechanisms were compared on natural and black anodized aluminium samples. Due to the different absorptiveness of both layers, the ablation threshold varies. Further more, the ablation mechanism investigated using microscopy and photoacoustic measurements, respectively, varies with the absorptivity .