In this study, chitin was deposited on AZ91 magnesium alloy at room temperature for 180 min, and then HA coating was applied as second layer for 180, 240, 300, 360, and 420 min by dipping method. The layers were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission-scanning electron microscopy (FE-SEM), as well as adhesion, nanohardness, and potentiodynamic polarization tests. XRD results analyzed by Williamson–Hall method revealed residual tensile and compressive strains in the chitin and HA coatings, respectively and with prolonged deposition time to 420 min, coating adhesion decreased. FTIR results indicated the presence of the chemical factors affecting the chitin and HA coatings. FE-SEM results indicated that prolonged deposition time resulted in increased coating density and formation of a porous structure of HA coating. Overall, the optimum corrosion resistance was observed for the sample with 300 min deposition time.