Shen Zihan,Yang Hongyi,Zhang Pengjie,Cui Jiewu,Wang Dongmei,Shen Wangqiang,Xu Guangqing,Lv Jun
Solving the problems of interfacial compatibility and dispersibility between filler and epoxy resin (EP) can greatly improve the anticorrosion performances of epoxy coatings and expand their application field. In this work, carbon nanotubes (CNTs) were modified by poly(sodium 4-styrene sulfonate) and poly(3,4-ethylenedioxythiophene) to form PCNTs hybrids, and the cathodic electrophoretic deposition method was used to form composite epoxy coatings on the surface of sintered NdFeB magnets for enhancing the anticorrosion performance. The corrosion resistance of PCNTs was evaluated by electrochemical and static immersion corrosion tests. Results indicate that PCNTs hybrids possess better distribution and compatibility in epoxy resin than CNTs hybrids, resulting in the anticorrosion performances of higher density of composite epoxy coatings on NdFeB magnets. Optimized EP/PCNTs possess a much higher \(\left| Z \right|\) 0.01 Hz of 4.41 × 10 7 Ω·cm 2 and a much lower J corr of 9.648 × 10 − 10 A·cm − 2 than that of EP (1.34 × 10 4 Ω·cm 2 and J corr 4.436 × 10 − 6 A·cm − 2 ), demonstrating superior corrosion resistance.
Xunwen Su,Liqun Zhu,Weiping Li,Haining Chen,Rui Cao,Huicong Liu
Al 2 O 3 -contained zinc coatings with enhanced protective and mechanical performances were prepared on NdFeB magnets by in situ electro-deposition methods from the zinc plating baths containing alumina sol. The positively charged alumina sol particles migrate to the NdFeB cathode and then gel along with zinc on the cathode surface, which changes the electro-deposition process of zinc. As a result, the surface morphology and phase structure of the zinc coating is significantly changed. The incorporation of alumina particles achieves a denser zinc coating with a smaller grain size and the hardness is well improved. By increasing alumina sol concentration in the plating bath, the micro-hardness and wear resistance of the zinc coatings gradually increased. What's more, the alumina sol addition also improved the corrosion resistance of zinc coatings. When 20 wt. % alumina sol is added, the corrosion potential of the zinc coating is positively shifted for 168 mV and the corrosion current was more than one order magnitude lower than the blank one. Therefore, this approach shows great promise to obtain alumina-contained zinc coatings with enhanced anti-corrosion properties and mechanical properties.
In this work, tannic acid (TA) was employed to modify the surface of multiwall carbon nanotubes (CNTs) to form TCNTs hybrids via noncovalent functionalization to enhance its dispersibility in water. Then, the TCNTs enhanced epoxy coatings were applied on sintered NdFeB magnets by cathodic electrophoretic deposition method for corrosion test. The corrosion resistance of prepared specimens was assessed by electrochemical experiments. The results show that TCNTs hybrids present a more homogeneous distribution in epoxy resin than pristine CNTs and could obviously promote anticorrosion properties of prepared specimens. Within 36-day soaking in 3.5 wt.% NaCl solution, the specimens maintain a high value of | Z | 0.01Hz (10 8 Ω cm 2 ) when the concentration of TCNTs is 2 g/L. When immersed in 3.5 wt.% NaCl solution for 40 days, the E corr of specimens shifts to − 0.207 V and J corr is about 5.281 × 10 −11 A cm −2 , which demonstrates superior corrosion resistance.
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