Insight into chelating agent stimulated in-situ growth of MgAl-LDH films on magnesium alloy AZ31: The effect of initial cationic concentrations

A 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 Al 3+ 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 Al 3+ concentrations showed better corrosion resistance and an interesting stable network structure on a flat surface both covered/consisting of very fine LDH flakes. • LDH films were grown in situ on AZ31 alloy in the presence of chelating agent. • The thermodynamic calculations of the LDH possibility formation were performed. • The effect of initial cationic concentrations on LDH formation is demonstrated.