Zn-5wt.%AI and Zn-3wt.%AI-2wt.%Mg model alloys were cast and heat treated in order to obtain specimens with distinct microstructure and identical chemical composition. The microstructure was characterized in detail using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX) and x-ray diffraction spectroscopy (XRD) to identify chemical composition, size and distribution of present phases. Mass loss of samples with different microstructure and identical chemical composition subjected to a cyclic corrosion test and a test under non-rinsing conditions differed by a factor of up to two. Some model alloys showed better corrosion performance compared to commercial coatings with similar composition tested in parallel. This indicates that microstructure modification can improve the corrosion performance of industrial zinc alloy coatings. The mechanism is discussed based on measurements of corrosion stability of individual phases, preferential corrosion, composition and stability of corrosion products, dc electrochemical characteristics and infrared absorption spectroscopy (IRRAS) experiments.