Effects of Sodium Hypophosphite on the Behaviors of Electrodeposited NiWP Alloy Coatings
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JMEPEG DOI: 10.1007/s11665-017-2807-3
Effects of Sodium Hypophosphite on the Behaviors of Electrodeposited NiWP Alloy Coatings Jinku Yu, Shen Zhai, Meiqi Yu, Hongling Luo, Qi Qiao, Jia Zhao, Zhefeng Xu, and Kazuhiro Matsugi (Submitted November 17, 2016; in revised form June 15, 2017)
In this paper, ternary NiWP alloy coatings were prepared by electrodeposition, and the effects of sodium hypophosphite (NaH2PO2) concentration on the properties of the coatings, including the deposition rate, current efficiency, composition, surface morphology, corrosion resistance, and microhardness, were investigated. Results reveal that the deposition rate and current efficiency are mainly dependent on the NaH2PO2 concentration in the plating bath. The deposition rate reaches a maximum value of 8.70 lm/h with a NaH2PO2 concentration of 10 g/L, whereas the total current efficiency decreases from 33.10 to 27.80%. As the concentration of NaH2PO2 increases, the grain size of the obtained coatings gradually decreases. Moreover, when the NaH2PO2 concentration is 6 g/L, the NiWP alloy coatings possess a microhardness value of 663.7 HV. Keywords
deposition rate, electrodeposition, microhardness, NiWP alloy coatings, sodium hypophosphite
1. Introduction Since their appearance, NiP alloys have been widely used, especially for binary NiP alloy coatings. NiP alloy coatings have been deeply investigated because of their excellent properties, such as good corrosion resistance, outstanding hardness, and high wear resistance (Ref 1-4). To increase their performance, some elements, such as tungsten (W), tin (Sn), copper (Cu), molybdenum (Mo), and chromium (Cr), are introduced into the Ni-P matrix to form ternary alloys (Ref 5, 6). The obtained ternary alloys possess enhanced physical and chemical properties; thus, they may be used in engineering applications. Among the ternary alloys, NiWP alloy coatings have been widely researched because of their superior properties, such as wear resistance, surface roughness, electric resistance, corrosion resistance, hardness, and strength. Up to the present day, many researchers focused on the basic knowledge of NiWP alloy coatings related to the microstructure, properties, and composition of NiWP alloy coatings. However, few researchers investigated their processing and engineering applications (Ref 7-12). To the authors knowledge, only a small part of the results of these studies have been converted into practical products desired by the society. Jinku Yu, Shen Zhai, Qi Qiao, and Jia Zhao, State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 Hebei, Peoples Republic of China; Meiqi Yu, Zhefeng Xu, and Kazuhiro Matsugi, Graduate School of Engineering, Hiroshima University, 1-4-1. Kagamiyama, HigashiHiroshima 739-8527, Japan; and Hongliang Luo, Graduate School of Engineering, Hiroshima University, 1-4-1. Kagamiyama, HigashiHiroshima 739-8527, Japan; and Hebei Provincial Key Laboratory of Heavy Machinery Fluid Power Transmission and Control, Yanshan Univers
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