Active corrosion protection of Mg-Al-PO43- LDH nanoparticle in silane primer coated with epoxy on mild steel

Mg-Al-PO43- layered double hydroxide (LDH) nanoparticle was synthesized through an anion exchange method and characterized by XRD, IR spectroscopy and SEM. The phosphate and Mg2+ release ability of Mg-Al-PO43- LDH in the 3.5 wt. % NaCI solution was measured by inductively coupled plasma-optical emission spectrometer (ICP-OES). Results showed the release of Mg2+ from the LDH scaffold along with phosphate anion from LDH gallery, illustrating importance of solubility rather than ion-exchange mechanism. Then, the corrosion inhibitive behavior of Mg-Al-PO43- LDH in 3.5 wt. % NaCI solution was assessed by electrochemical measurements and FE-SEM in comparison with the Mg-Al-NO3- LDH. The results showed that Mg-Al-PO43- LDH forms inhibitive film on the mild steel and significantly mitigate corrosion compared to Mg-Al-NO3- LDH. The LDHs were also employed in a silane primer top-coated by epoxy-polyamide on mild steel. The results of electrochemical measurements showed significant active corrosion protection ability of Mg-Al-PO43- LDH in the coating with an artificial defect. Furthermore, the adhesion strength of the coating including Mg-Al-PO43- LDH to mild steel after exposure to salt spray (5% NaCI solution) was improved. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.