Materials Reports 2022, Vol. 36 Issue (Z1): 22010229-6 |
METALS AND METAL MATRIX COMPOSITES |
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Research on Manganese-based Phosphate Conversion Coating on AZ91D Magnesium Alloy: the Effect of Various Components and Contents of Phosphating Solution on Corrosion Resistance |
ZHANG Shudi, HE Huanhuan, XU Yuheng, XU Yang
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School of Environmental and Chemical Engineering, Shenyang Ligong University, Shenyang 110159, China |
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Abstract This research was aimed to explore the influence of different additives on the corrosion resistance of phosphating coatings, and to improve the corrosion resistance of manganese-based phosphating coatings on magnesium alloys. The manganese-based phosphating film was prepared on the surface of AZ91D magnesium alloy by the chemical conversion method. The influence of the composition and content of the phosphating solution on the corrosion resistance of the phosphating film was explored, and the surface morphology and composition of the film were characterized by SEM and EDS analyses. The optimum mass concentration of each component in phosphating solution was 35 g/L MnSO4, 30 g/L NaH2PO4, 0.5 g/L EDTA-4Na, 1 g/L NaF, and 2 g/L NaNO3 (pH=2.5 with phosphoric acid). In the SEM image, the magnesium alloy phosphating film displayed an obvious double-layer film structure, and the thickness of the film layer was about 24 μm. Through SEM observation, the thicker the optimized phosphating film, the more dense surface and fewer cracks were found. It was observed in the EDS diagram that after the addition of NaF, the composition of the film layer changed, and a small number of F element participated in the film formation. Compared with the basic phosphating film, the corrosion resistance of the optimized phosphating film was enhanced, the corrosion current density was reduced from 8.912×10-7 A/cm2 to 5.56×10-7 A/cm2, and the capacitive arc radius was also significantly increased. Overall, the corrosion resistance performance was greatly improved.
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Published: 05 June 2022
Online: 2022-06-08
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Fund:National Natural Science Foundation of China (51771050). |
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