CoxFe3-xO4@SDBS@KH-560 nanocontainers-engineered MAO coatings on AZ31B magnesium alloy: Microstructure regulation, corrosion protection and self-healing behavior

Hollow Co x Fe 3-x O 4 nanocontainers were loaded with SDBS and sealed by KH-560. • Nanocontainers participated in MAO growth and regulated discharge defects. • The specific wear rate of MAO-1 decreased by 95.8% compared with MAO-0. • MAO-1 showed the best corrosion resistance with superior electrochemical properties. • SVET confirmed corrosion-responsive inhibitor release and self-healing protection. The intrinsic porosity and microcracks inherent to micro-arc oxidation (MAO) coatings create preferential diffusion paths for corrosive species, thereby limiting the long-term corrosion protection of magnesium alloys. In this work, hollow mesoporous Co x Fe 3-x O 4 nanocontainers were synthesized via a cetyltrimethylammonium bromide (CTAB) assisted solvothermal method, loaded with sodium dodecylbenzenesulfonate (SDBS) as a corrosion inhibitor, sealed with KH-560 silane coupling agent, and subsequently incorporated into MAO coatings on AZ31B magnesium alloy. The nanocontainers participated in coating formation through pore filling and co-solidification with molten oxides. Moderate addition refined discharge pores and improved coating integrity, whereas excessive addition caused particle agglomeration and inhomogeneity. At the optimal concentration of 1   g·L -1 , MAO-1 exhibited the greatest coating thickness (37.96 μm). MAO-1 exhibited the highest coating resistance ( R c = 2.40×10 7 Ω·cm 2 ) and charge-transfer resistance ( R ct =1.77×10 6 Ω·cm 2 ), together with the lowest corrosion current density (2.85×10 -9   A·cm -2 ). Its specific wear rate was reduced to 2.56×10 −6 mm 3 ·N -1 ·m -1 , which is 95.8% lower than that of MAO-0. Scanning vibrating electrode technique (SVET) measurements further confirmed corrosion-responsive self-healing behavior in MAO-1: after 12   h of immersion, the maximum local potential-difference signal decreased from 0.0105 to 0.0042   mV, representing a 66.1% reduction compared to MAO-0. The progressive attenuation of local electrochemical activity indicates that the release, migration, and interfacial adsorption of SDBS effectively suppress localized anodic dissolution and partially restore protection at damaged regions. Overall, the Co x Fe 3-x O 4 @SDBS@KH-560 nanocontainers synergistically combine barrier reinforcement with inhibitor-mediated active protection, thereby enhancing the corrosion resistance, wear resistance, and self-healing capability of the MAO coating.