The effects of 8-hydroxyquinoline on corrosion performance of a Mg-rich coating on AZ91D magnesium alloy

• Mg-HQ-rich primer is prepared by adding hydroxyquinoline in Mg-rich epoxy coating.
• The 8-HQ combines with Mg2+ in the coating and forms insoluble complex MgQ2.
• The MgQ2 layers on Mg particles retard dissolution and extend cathodic protection.
• MgQ2 also blocks defects in the primer and the active sites on substrate surface.
• The Mg-HQ-rich primer shows obviously better protection for AZ91D alloy.

A Mg-HQ-rich primer was prepared by adding 45% pure magnesium particles and 5% 8-hydroxyquinoline in epoxy coating. The Mg-HQ-rich primer showed obviously better protection for AZ91D alloy than 50% Mg-rich primer. The additive 8-HQ combines with Mg2+ in the coating, forming a insoluble complex, MgQ2, instead of Mg(OH)2 on Mg particles. The MgQ2 layer may retard dissolution of magnesium particles and prolong the cathodic protection effect of Mg-HQ-rich primer. Additionally, the corrosion products may also block the defects in the primer and the active sites on the substrate surface, thereby further increase the corrosion resistance of the Mg-HQ-rich primer.