Aluminum doped zinc oxide (ZnO:Al) films were deposited by sputtering on borosilicate glass (sodium poor) and soda lime glass (sodium rich). These films were exposed up to 1032 hours of damp heat (85 ◦C/85 % relative humidity) to study the influence of among others the sodium content of the substrate on the ZnO:Al stability. A decrease in mobility, an increase in resistance and small changes in carrier concentration and absorption at wavelength ranges from 1500-2400 nm were observed for both types of samples. Furthermore, small spots were formed on the surface after damp heat exposure on both types of samples. Moreover, the sodium rich samples
displayed whitening of all edges, due to the formation of fractal-like structures. No further differences between the sample types were observed.