| XIA Ri-hui,WANG Chun-xia,TIAN Li-xi.Effects of Impurity Copper Ions on the Morphology and Corrosion Resistance of Electroplated Nickel Layer[J],51(10):276-283, 343 |
| Effects of Impurity Copper Ions on the Morphology and Corrosion Resistance of Electroplated Nickel Layer |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.10.029 |
| KeyWord:copper ions electroplated nickel surface topography crystal texture corrosion resistance electro-deposition |
| Author | Institution |
| XIA Ri-hui |
School of Material Science and Engineering, Nanchang Hangkong University, Nanchang , China |
| WANG Chun-xia |
School of Material Science and Engineering, Nanchang Hangkong University, Nanchang , China |
| TIAN Li-xi |
School of Material Science and Engineering, Nanchang Hangkong University, Nanchang , China |
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| Abstract: |
| The work aims to study the effects of copper ion impurities in nickel plating solution on the microstructure and corrosion resistance of electroplated nickel layer. In the form of copper sulfate pentahydrate, different mass concentration (5, 10, 30 mg/L) of copper ions were introduced into the nickel plating solution as copper ion impurity, and compared with the initially prepared nickel plating solution (0 mg/L Cu2+) as a blank group. Low current density (0.5 A/dm2) was used to electroplate nickel layer on Q235 steel, then scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical analysis techniques were used to characterize and analyze the surface micromorphology, crystal texture, chemical state information of various elements on the surface and corrosion resistance of different electroplated nickel layers. The results showed that the electroplated nickels layer gradually became gray, and the appearance quality decreased when the concentration of copper ions in the nickel plating solution increased; when the content of copper ions in the nickel plating solution was within the industrial tolerance range (≤10 mg/L), the nickel layer was bright in color, while the crystal grain size was small and uniform. When the concentration of copper ions was greater than the industrial tolerance, the crystal grains began to become coarser, and the size was not uniform. The growth mode of nickel crystal remained unchanged, which grew in the form of spiral dislocation. The copper ion in the plating solution changed the nickel crystal structure, the diffraction angle for the main peak shifted to a large angle, the half peak width increased gradually, and the crystal plane spacing decreased. At the same time, it affected the preferred growth orientation of nickel crystal, the grain growth gradually changed from (111) and (200) planes to (111) and (220) planes. XPS test results showed that the increase of copper ion concentration led to the decrease of nickel precipitation efficiency. Copper ions precipitated in the nickel layer and existed in the nickel layer in the form of elemental copper and copper oxide. The electrochemical test results showed that the copper ion in the nickel plating solution reduced the corrosion resistance of the nickel layer. With the increase of copper ion concentration from 0 mg/L to 30 mg/L, the open circuit potential (OCP) of nickel layer in 3.5wt.% NaC1 solution gradually decreased, the self-corrosion potential decreased from −0.487 mV to −0.547 mV, the self-corrosion current density increased from 7.898 9 μA/cm2 to 17.316 μA/cm2, the electrochemical impedance modulus and phase angle became smaller, and the charge transfer resistance (Rct) decreased from 1 798 Ω.cm2 to 851 Ω.cm2. In summary, trace copper ion impurities in watt solution will lead to coarse nickel crystal and gray appearance of the coating. The impurity copper atoms in the nickel layer will cause a certain degree of lattice distortion, reduce the lattice constant and change the preferred orientation of grain growth. With the increase of copper ions impurity concentration, the self-corrosion current density increases, the impedance value decreases accordingly, and the corrosion resistance decreases in 3.5wt.% NaCl solution. |
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