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A manganese oxide contained coating was prepared on biodegradable AZ31B magnesium alloy to control the degradation of AZ31B and improve its biocompatibility. Morphology, composition, and corrosion resistance of the coating were studied. The SEM observations showed that the coating was approximately 4–6 μm in thickness with net-like microcracks. The XPS analysis indicated that the coating was mainly composed of MgO, Mg(OH)₂, MnO₂, Mn₂O₃, and Mn₃O₄. It was found that AZ31B with such coating showed better corrosion resistance in simulated blood plasma through electrochemical and immersion tests. The hemolytic assay indicated that the treated AZ31B had no hemolytic effect.

Influence of surfactants on the corrosion properties of chromium-free electroless nickel deposit were investigated on AZ91D magnesium alloy. The corrosion tests were carried out by immersion test (1 M HCl) and electrochemical polarization test (3.5 wt% NaCl). The surfactants in the electroless nickel bath increases the corrosion resistance properties of the deposit on the magnesium alloy. In addition, smoothness and amorphous plus nano-crystalline phase were increased and accounted for the significant corrosion resistance. As a consequence, the corrosion potential moved towards the positive direction and the corrosion current density decreased. The immersion tests also provided the same trend as that of electrochemical polarization test. On the whole, the study concluded that corrosion resistance was enhanced by including a surfactant in the electroless deposits on magnesium alloy.

In the chemistry conversion of the solution of CeCl₃–NaCl, the concentration of Cl^- affects the property of cerium-based conversion coating. Hence, we have ascertained the most appropriate concentration of Cl^- in the paper. Firstly, to prepare a cerium-based conversion coating in the solution of CeCl₃–NaCl on ZM–C5 alloy, we conducted the experiment by the simple immersion method. Secondly, the mass of the specimen was measured with a BS224S electronic scale. Finally, the corrosion resistance of the coating was evaluated by the dropping test. The results show that when the concentration of Cl^- is between 0 to 15 g·dm^–3, the smoothness, compactness and adhesion of the conversion coatings are better and that the most appropriate concentration of Cl^- is 10 g·dm^–3 by the dropping test. The conclusion can be drawn that the corrosion resistance of the coating is best by the simple immersion method in the solution which the concentration of cerium chloride is 3 g·dm_–3 and the concentration of sodium chloride is 10 g·dm_–3.

The molybdate conversion coating for 6063 aluminum alloy was prepared with Na₂MoO₄·and K₂ZrF₆ via the dip process. The physical and chemical properties of conversion coating were analyzed by CuSO₄ dropping corrosion test, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS). The optimized process conditions are as follows: Na₂MoO₄·2H₂O 6 g/L, K₂ZrF₆ 3 g/L, pH 3, temperature 40 °C, and reaction time 10 min. The conversion coating exhibits yellow color and consists of Mo, Zr, Mg, Al, O.