| FU Chuan-qi,HUANG Ya-zhong,LI Sheng-jun,XIANG Yong-kuang.Study on Preparation and Corrosion Resistance of Ni-P/Ni-Zn-P Three-layer Composite Coating[J],50(12):400-407 |
| Study on Preparation and Corrosion Resistance of Ni-P/Ni-Zn-P Three-layer Composite Coating |
| Received:December 01, 2020 Revised:May 24, 2021 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2021.12.040 |
| KeyWord:low-phosphorus Ni-P coating high phosphorus Ni-P coating Ni-Zn-P coating three-layer composite coating chemical plating corrosion resistance polarization curve |
| Author | Institution |
| FU Chuan-qi |
School of Mechanical Engineering, Dalian , China |
| HUANG Ya-zhong |
School of Physical Science and Technology, Dalian University, Dalian , China |
| LI Sheng-jun |
School of Physical Science and Technology, Dalian University, Dalian , China |
| XIANG Yong-kuang |
School of Physical Science and Technology, Dalian University, Dalian , China |
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| Abstract: |
| Multi layer anode Ni-P/Ni-Zn-P composite coatings with different potential difference were prepared. A three-layer composite coating was prepared on the surface of Q235 low-carbon steel substrate by electroless plating, the inner layer was low-phosphorus Ni-P alloy, the middle layer was high-phosphorus Ni-P alloy, and the outer layer was Ni-Zn-P alloy coating. The surface morphology, composition structure and corrosion potential of the composite coating were analyzed by metallographic microscope, scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), X-ray diffraction (XRD) and electrochemical workstation. Compared with the the low-phosphorus Ni-P coating and the high-phosphorus Ni-P coating, the three-layer Ni-P/Ni-Zn-P composite coating has uniform cell size, and the cells are dense and smooth. The thickness of the inner layer of low phosphorus Ni-P coating is about 14.5 μm, the mass fraction of nickel is about 96.5%, and the mass fraction of phosphorus is 3.5%. The section thickness of the middle layer high phosphorus Ni-P coating is about 17.6 μm, the mass fraction of nickel is about 90.2%, and the mass fraction of phosphorus is about 9.8%. The total section thickness of Ni-P/Ni-Zn-P composite coating is about 40 μm, the mass fraction of nickel is about 80.7%, the mass fraction of zinc and phosphorus are 7.6% and 11.7%, respectively. In Tafel polarization curve, the corrosion current density of Ni-P/Ni-Zn-P composite coating is the smallest, which is 3.815×10–6 A/cm2 and has better corrosion resistance. After 220 h corrosion in simulated seawater 5%NaCl solution, the inner layer and middle layer were corroded into pieces, with holes and pitting corrosion. However, the Ni-P/Ni-Zn-P three-layer composite coating almost had no corrosion, only some of them had pitting corrosion, which indicated that the three-layer coating had better corrosion resistance than single-layer and double-layer coating. The preparation of multi-layer anode Ni-P/Ni-Zn-P composite coating with different potential difference has better performance and the corrosion rate is significantly reduced compared with the inner single layer and the middle double layer Ni-P alloy coating, and the corrosion resistance is better. |
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