AbstractA strategy based on chelating agent addition was used to assist the in-situ growth of MgAl-layered double hydroxides (LDHs) films on magnesium alloy AZ31 in a relatively mild condition. The growth behavior of MgAl-LDH films was studied on the magnesium alloy AZ31 substrate as the sole source of Al3+ and/or adding aluminum compounds as a supplementary source of respective ions. The composition, structure, corrosion resistance, and formation mechanism of LDH films were investigated and discussed. Results showed that the LDH-coated samples could effectively retard the corrosion of magnesium alloy. A thicker Mg (OH)2/MgAl-LDH composite film with larger flake size was formed without additional aluminum source. MgAl-LDH film fabricated with moderate additional Al3+ concentrations showed better corrosion resistance and an interesting stable network structure on a flat surface both covered/consisting of very fine LDH flakes.