Response to comments

AZ alloy is tested in simulated body fluid electrolyte. AZ series magnesium alloys contain 3 to 9 % aluminum. The latter has been suspected of causing multiple health problems, including dementia and autism. Aluminum containing magnesium alloys have been excluded from the list of potential candidates for bioresorbable implants. It is pointless to test aluminum containing magnesium alloys in SBF.  Yes, Al is harmful to health when the content is high. Whereas, AZ31 Mg alloy was also used in other researches. For example, the reference: Laura C. Córdoba, Christophe Hélary, Fátima Montemor, Thibaud Coradin, Bi-layered silane-TiO2/collagen coating to control biodegradation and biointegration of Mg alloys, Materials Science and Engineering: C, 94, 2019, 126-138. Another reference: Changgang Wang, Liping Wu, Fang Xue, Rongyao Ma, Ini-Ibehe Nabuk Etim, Xuehui Hao, Junhua Dong, Wei Ke, Electrochemical noise analysis on the pit corrosion susceptibility of biodegradable AZ31 magnesium alloy in four types of simulated body solutions, Journal of Materials Science & Technology, 2018, 1876-1884. In addition, the present work is our preliminary work. We want to test the corrosion performance of the HT film as biologic coating in SBF and compare it to the corrosion behavior in NaCl solution. Hence, we also use AZ31 alloy in this work to ensure the same condition with previous work (Chen, J.; Song, Y.W.; Shan, D.Y.; Han, E.H. Modifications of the hydrotalcite film on AZ31 Mg alloy by phytic acid: The effects on morphology, composition and corrosion resistance. Corros. Sci. 2013, 74: 130-138). Now, we are doing some research on the Mg-Fe HT-like film on the MgZn and MgCa series alloys.