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Corrosion behaviour of arc sprayed high Al content of Zn55Al coatings on Q235 steel in 3.5 wt% NaCl solution
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Beihang University

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National Key Research and Development Programme of China (No. 2016YFB0300901)

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    Abstract:

    In this work, a Zn55Al coating was deposited on Q235 steel by arc spraying high Al content Zn55Al pseudo-alloy wires formed by multi-core canned hot extrusion and a cold drawing method. The microstructure of the Zn55Al pseudo-alloy wire was investigated by scanning electron microscopy (SEM) and micro-region X-ray diffraction (Micro-XRD). The corrosion behaviour of the Zn55Al coating and pure Al coating as well as the Zn15Al coating were investigated by an immersion corrosion test and electrochemical measurements, and the difference between the coatings was also assessed. The results indicated that Zn55Al pseudo-alloy wires were composed of pure Zn and pure Al. An alloying phenomenon did not occur in the whole formation process. The Zn55Al coating that contained Zn-rich phases and Al-rich phases exhibited an obvious lamellar structure with a few holes and gaps. After 20 days of immersion, it was found that the Zn55Al coating formed a dense passive film and had better corrosion resistance than the Zn15Al coating. The corrosion potential (Ecorr) of the Zn55Al coatings was approximately 80 mv, which is more positive than that of the Zn15Al coatings but is more negative than that of the pure Al coatings and the Q235 substrate. The results of galvanic corrosion test also showed that the Zn55Al coating can provide better electrochemical protection than Zn15Al coating to the Q235 substrate. This suggested that Zn55Al coating displays not only a better corrosion resistance but also a stronger electrochemical protection to the Q235substrate. The protective mechanisms of the Zn55Al coating were also discussed.

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[Fengshangbin, Jialina, zhanghuarui, wangfangfang, liuguangxu, zhanghu. Corrosion behaviour of arc sprayed high Al content of Zn55Al coatings on Q235 steel in 3.5 wt% NaCl solution[J]. Rare Metal Materials and Engineering,2019,48(4):1087~1095.]
DOI:10.12442/j. issn.1002-185X.20170954

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History
  • Received:October 23,2017
  • Revised:January 04,2018
  • Adopted:January 08,2018
  • Online: May 13,2019
  • Published: