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Magnesium and its alloys have the advantages of high specific strength and specific stiffness, excellent thermal conductivity and vibration damping performance. However, due to their low corrosion potential and loose corrosion product film, the corrosion resistance of Mg alloys is poor, which seriously limits their utilization scope. In this paper, the corrosion resistance (CR) of AM60 alloy is investigated by adding 2.0 wt% Ca with subsequent thermal oxidation and Carbonation (TOC) at 400 °C for 15 h with different O₂/CO₂ ratios. Electrochemical impedance spectra and cross-sectional corrosion analysis reveal that the CR is much improved with the optimal O₂/CO₂ ratio of 1:3. This enhancement is attributed to the formation of a high-quality dual-layer protective structure, consisting of an outer MgCO₃/CaCO₃ composite layer and an inner MgO/CaO/Al₂O₃ composite layer. This protective film effectively mitigates micro-galvanic corrosion and provides resistance against Cl⁻ attack, contributing to the alloy's superior corrosion performance.

Though high-capacitance transition metal oxides are considered as promising pseudocapacitive materials to achieve high-energy storage for supercapacitors, the practical capacitance is far from the theoretical values because of their intrinsic poor abilities about the electronic and ionic transports. Here, to tackle these problems, we develop a hybrid nanostructured electrode in a facile process, in which layer-structured δ-MnO2 nanosheets are anchored onto seamless three-dimensional Ni nanocylinder arrays. The resultant Ni/δ-MnO2 nanocylinder arrays exhibit high specific capacitance up to 883.2 Fg−1 at a scan rate of 10 mVs−1 and achieve high energy density about 108 Whkg−1 at a power of 2.4 kWkg−1. The improved electrochemical performance mainly benefits from the vertically aligned Ni/δ-MnO2 hybrid structure. Owing to such a hybrid structure the ion/electron transports are facilitated along the nanocylinders due to the reduction in the transport distance, and large accessible surface area is also provided for anchoring more high-capacitance materials. Moreover, the additional contact resistance can be dramatically reduced owing to the large interplanar spacing of δ-MnO2 and ordered semicoherent interface of Ni/δ-MnO2. Keywords: Supercapacitor, Hybrid electrode, Ni nanocylinder arrays, δ-MnO2, 3D nanostructure