Superior corrosion protection and adhesion strength of epoxy coating applied on AZ31 magnesium alloy pre-treated by PEO/Silane with inorganic and organic corrosion inhibitors

[Display omitted] •PEO/Silane containing inhibitors as pretreatment of epoxy layer.•Studying active corrosion protection of inhibitors by EIS and EN tests.•Best protective properties for three-layer coating with Ce and 8-HQ inhibitors.•Improvement of wet adhesion strength of three-layer coating with Ce and 8-HQ. PEO/Silane/Epoxy coating system with inorganic inhibitor (Ce(NO3)3) in the plasma electrolytic oxidation (PEO) layer as well as organic inhibitors in the silane layer was investigated in terms of active corrosion protection properties and adhesion strength. The results of electrochemical impedance spectroscopy (EIS), electrochemical noise (EN) and pull-off tests indicated that the presence of the 8-Hydroxyquinoline (8-HQ) organic inhibitor provides the optimal performance for coating systems. The formation of Ce(OH)3 in the PEO coating structure and the complex chelate of Mg(HQ)2 in the silane layer lead to the creation of active corrosion protection properties for the coating systems.