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Influence of substrate composition on the formation of phytic acid conversion coatings

Authors

  • X. Cui,

    1. School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (P. R. China)
    2. State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (P. R. China)
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  • G. Jin,

    Corresponding author
    1. School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (P. R. China)
    • School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (P. R. China).
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  • E. Liu,

    1. School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (P. R. China)
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  • M. Ding,

    1. School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (P. R. China)
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  • Q. Li,

    1. School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (P. R. China)
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  • F. Wang

    1. School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (P. R. China)
    2. State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (P. R. China)
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Abstract

In this paper, the formation and corrosion resistance of the phytic acid conversion coatings on Mg, Al, and AZ91D magnesium alloy were contrastively investigated using scanning electronic microscopy (SEM), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR), electronic probe microscopic analyzer (EPMA), electronic balance, and electrochemical methods. The influence of phytic acid conversion coating as a middle layer on the properties of the paint on magnesium alloys was also investigated.

The results show that the formation process of the conversion coatings is evidently influenced by the compositions of the substrate. The coating on pure aluminum is thinner and compacter than that on pure magnesium and the coating formed on α phase in AZ91D magnesium alloy is thinner but denser than that on β phase. The phytic acid conversion coatings formed on Mg, Al, and AZ91D magnesium alloy can all increase their corrosion resistance. The active functional groups of hydroxyl and phosphate radical are rich in the conversion coatings, which can improve the bonding between the organic paint and magnesium alloy and then improve their corrosion resistance.

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