A new method for electroless Ni-P plating on AZ31 magnesium alloy |
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Authors: | Hui Zhao Jianzhong Cui |
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Affiliation: | a Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, Liaoning, China b Environmental Corrosion Center, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 |
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Abstract: | Coating Ni-P films on AZ31 magnesium alloys via electroless plating and organic coatings (organsilicon heat-resisting varnish), was studied. An organic coating was proposed as the interlayer between Ni-P coating and AZ31magnesium alloy substrate, to replace the traditional chromium oxide plus HF pretreatment. The Ni-P deposited on the interlayer was also characterized by its structure, morphology and corrosion-resistance. The interlayer on the substrate not only reduces the corrosion of magnesium during Ni-P plating process, but also reduces the potential difference between the matrix and the second phase. The result of the cross-cut test indicates the adhesion between the substrate and the interlayer is good enough. A Ni-P film with fine and dense structure was obtained on the AZ31 magnesium alloy. The electrochemical measurements show that the sample with Ni-P film exhibits lower corrosion current density and more positive corrosion potential than the substrate. Furthermore, the Ni-P coating on the AZ31 magnesium alloy exhibits high corrosion resistance in the rapid corrosion test illustrated in this paper. The method proposed in this work is environmentally friendly: no fluoride or hexacalent chromium compounds are used. In addition, it provides a new concept for plating the metals, which are considered difficult to plate due to high reactivity. |
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Keywords: | Organic coatings Interlayer Ni-P film Electroless plating Corrosion resistance |
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