Anodic oxide films formed on aluminum by anodizing in alkaline solution is generally recognized to show higher protective performance against dissolution under alkaline environmental conditions. In this study, electrochemical impedance spectroscopy (EIS) was applied to evaluate the time variations of charge transfer resistance, R_ct for the anodically oxidized aluminum during the immersion in alkaline environment. Also SEM, FIB-SIM, and TEM observations were employed to investigate pit morphology for each stage of the dissolution process. It was found that the films formed by anodizing in sodium carbonate (Na₂CO₃, pH=11.5) solution showed higher resistance against alkaline dissolution than the films formed in ammonium tartrate ((NH₄)₂C₄H₄O₆, pH=6.7) solution or sulfuric acid (H₂SO₄, pH=0.0) , because of the high corrosion performance of the barrier layer. The R_ct increased as the thickness of the barrier layer increased.

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In order to possess magnetic properties in the Mg-based composite materials, pure magnesium and Ni–Cu–Zn ferrite (FR) powders were mechanically alloyed (MAed) using a vibrational ball mill, and the produced composite powders were consolidated into the bulk materials by spark plasma sintering (SPS) . Solid-state reaction, hardness, microstructure and magnetic properties of the bulk materials were characterised by X-ray diffraction, Vickers hardness, optical microscopy and vibrating sample magnetometer, respectively. Solid-state reactions between Mg and FR in the bulk materials occurred to form α-Fe and MgO at a sintering temperature of 673 K. In contrast, the formation of Fe₃C occurred at 773 K and 873 K. The Vickers hardness of the bulk materials fabricated from MAed 8 h powder at 773 K showed the highest value of 198 HV. This is due to an increase of composite phases formed the intermetallic compounds, such as MgO, α-Fe and Fe₃C as increasing MA time. The magnetic property (magnetization) of the bulk materials fabricated at 673 K exhibited the highest value of 1.0×10⁻⁵ Wbm/kg due to the formation of α-Fe. The magnetic property (magnetization) of the bulk materials decreased due to the formation of Fe₃C as increasing sintering temperature. Ferromagnetism of the Mg-based composite materials was enhanced by the formation of the α-Fe and Fe₃C.

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The effect of cooling rate during solidification on corrosion resistance of aluminum alloy fin stock for automotive heat exchangers has been investigated. Constituent particles become much finer and denser with increasing of cooling rate, but, the area function of secondary phase particle did not change. Corrosion rate did not change with becoming finer and denser of secondary phase particle in Al–0.7mass%Fe–1.5mass%Zn alloy, because, Al₃Fe particles themselves worked as a cathode. On the other hand, corrosion rate increased in the cases of Al–1.0mass%Mn–0.4mass%Fe–1.5mass%Zn alloy, because, matrix/Al₆ (Mn, Fe) interface acts as a more active cathode than particles themselves.

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