In this paper, the effect of sodium phosphate salt concentration in the electrolyte on the electrochemical behavior and microstructure of plasma electrolytic oxidation coating formed on the 2024 aluminum alloy is studied. In order to evaluating the corrosion behavior, samples are immerged in 3.5 wt. % NaCl solution and then potentiodynamic polarization test and electrochemical impedance spectroscopy measurement are conducted. The microstructure of ceramic coating are investigated by X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) images. According to the results of corrosion tests can be found that increasing the concentration of sodium phosphate weaken the corrosion behavior of coating. Also, XRD pattern is shown the formation of ceramic compounds on the substrate. From SEM images can be concluded that increasing the sodium phosphate concentration in the electrolyte, leads to increasing the surface porosities and decreasing the thickness and quality of coating.