The improved performance of Mg-rich epoxy primer on AZ91D magnesium alloy by addition of ZnO

• ZnO was added in Mg-rich epoxy primer to improve the protection for AZ91D Mg alloy.
• Mg–ZnO-rich primer showed good conductivity with reduced dissolution of Mg particles.
• ZnO improved physical crosslink density and barrier property of the epoxy matrix.
• The primer with 40% Mg and 10% ZnO showed better protection and prolonged lifetime.

ZnO particles were added in Mg-rich epoxy primer to improve the protection for AZ91D magnesium alloy. The well dispersed ZnO particles could play a role in electrical conduction instead of Mg particles, consequently the Mg–ZnO-rich primer exhibited good conductivity while the dissolution rate of Mg particles decreased. ZnO particles also improved physical crosslink density of the epoxy matrix, which could reduce defects and enhance the barrier property and adhesion of the coating. As the results, the epoxy primer with 40 wt.% Mg and 10 wt.% ZnO showed better protection and prolonged lifetime than the primer with 50 wt.% Mg.