Highly corrosion-resistant ZIF-8-integrated micro-arc oxidation coating on Mg alloy

Abstract

The long-term corrosion resistance of conventional micro-arc oxidation (MAO) coatings on magnesium alloy is limited by the inherent micro-scale pores. To address this issue, zeolitic imidazolate framework-8 (ZIF-8) and zinc gluconate (ZnG) loaded ZIF-8 (ZnG@ZIF-8) were synthesized and incorporated into the MAO coating. The electrochemical and immersion tests showed that the MAO composite coating doped with ZIF-8 and ZnG@ZIF-8 ((ZIF-8 + ZnG@ZIF-8)/MAO) displayed optimal corrosion resistance. The corrosion current density (jcorr) of the pristine (ZIF-8 + ZnG@ZIF-8)/MAO composite coating (3.38 nA cm−2) is 63.3 times lower than that of the blank MAO coating (214 nA cm−2), indicating the significant enhancement in corrosion protection of the nanoparticle to the coatings. Even after 32 days of immersion in a 3.5 wt.% NaCl solution, the jcorr of the former was as low as 87.3 nA cm−2, much lower than that of the blank MAO coating (1710 nA cm−2). These findings provide new insights into the design of corrosion-resistant MAO composite on magnesium alloy surfaces via the incorporation of inhibitor-loaded ZIF-8 nanocontainers.