Active protection of Mg alloy by composite PEO coating loaded with corrosion inhibitors

Abstract

A PEO (Plasma Electrolytic Oxidation) /Sol-gel composite coating was prepared on AZ91 magnesium alloy. The porous layer produced by PEO was loaded with corrosion inhibitors (sodium salts of glycolic, 4-aminosalicylic and 2,6-pyridinedicarboxylic acids). Sealed with a thin sol-gel layer, this sandwich-like structure demonstrated durable barrier and active corrosion protection as shown by electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The active protection mechanism ensures self-healing ability of the coating system, which was obtained by suppression of the re-deposition of impurity and/or adsorption of the impregnated inhibitors upon the exposed surface.