Ceramic particle reinforced aluminum metal matrix composites (MMCs) have resulted in potential use in aerospace and automobile industries. The composites have been processed by mechanical milling followed by traditional powder metallurgy route. The Al crystallite size is reduced to 27 nm after 60 h of milling. Results of the corrosion tests, evaluated using the potentiodynamic method in the NaCl solution, indicate that corrosion of the investigated composite materials depends on the weight fraction of the reinforcing particles. It has been found out, based on the determined anode polarization curves, that the investigated materials are susceptible to pitting corrosion. Moreover, experimental results suggest that the milled composite material Al-Zn/Al2O3p has higher corrosion resistance in the selected environment compared to unmilled composite Al-Zn/Al2O3p. Polarization curves show that the milling procedure improves the composite corrosion resistance in passive conditions. This is illustrated by the corrosion potential, which becomes nobler with milling.