Corrosion protection of NdFeB magnets by phosphating with tungstate incorporation

Takeuchi, S.M. Tamborim; Azambuja, Denise Schermann; Saliba-Silva, Adonis Marcelo; Costa, Isolda

doi:10.1016/j.surfcoat.2005.10.029

Cited by 68 publications

(20 citation statements)

References 25 publications

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“…According to Fig. , the Bode plots show two time constants whose maximum phase angle was around −50°, attributed to the process under mass transport control, characteristic of phosphating layers …”

Section: Resultsmentioning

confidence: 99%

“…For these layers, the capacitance was replaced by a CPE due to the coating characteristics. In this case, the overall impedance is given by the sum of the two layers corresponding to the impedance values and is characterised by a parallel combination of the capacitance and resistance of each layer, as proposed in the literature …”

Section: Resultsmentioning

confidence: 99%

“…Chromatising is the most effective conversion coating treatment used for sealing the pores of phosphating coatings . This treatment improves corrosion resistance due to the deposition of insoluble chromates in the pores and passivation of exposed metal .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Black wattle tannin as a zinc phosphating coating sealer

Peres

Cassel

Ferreira

et al. 2013

Surface & Interface Analysis

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This paper reports an investigation into the use of condensed black wattle tannin as an environmental friendly sealer after zinc phosphating of carbon steel. In order to verify the sealer efficiency against corrosion, electrochemical impedance spectroscopy, potentiodynamic polarisation and salt spray tests were performed. To verify the pore modifications and phase compositions, SEM, electron dispersive spectroscopy and X‐ray diffraction analysis were carried out. The influence of the sealer on the adherence of finishing coatings was analysed. The results show that the tannin/sealer did not affect the final coating adhesion and improved the corrosion resistance of sealed samples. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Black wattle tannin as a zinc phosphating coating sealer

Peres

Cassel

Ferreira

et al. 2013

Surface & Interface Analysis

View full text Add to dashboard Cite

show abstract

“…Attempts such as alloy additions 3, 8–12 and surface treatment 13–25 have been used to improve the corrosion resistance of the NdFeB magnet, of which the electroplating of metal coatings is one of the most popular methods 19–23. While the reported papers show that most of the coatings on the sintered NdFeB magnet are cathodic coatings 19–23, and seldom anodic coatings 24, 25.…”

Section: Introductionmentioning

confidence: 99%

Corrosion resistance of environment‐friendly sealing layer for Zn‐coated sintered NdFeB magnet

Liu

Yang

et al. 2011

Materials & Corrosion

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In this paper, a protective sealed Zn coating (SZC) was prepared on sintered NdFeB magnet by the combination of electrodeposition and sol-gel method. The unsealed Zn coating (UZC) was also studied for a comparison. The surface morphology of UZC and the cross-section morphology of SZC were investigated using scanning election microscope (SEM). The microstructure of Zn coating and structure of sealing layer were studied by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectrum, respectively. The corrosion characteristics of SZC and UZC in neutral 3.5 wt% NaCl solution were evaluated using electrochemical measurements including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test, indicating that the anticorrosive properties of SZC coated specimens increased 20 times compared with that of UZC coated specimens. In order to further investigate the anticorrosive properties of SZC, a long-term immersion test was carried out in neutral 3.5 wt% NaCl solution using EIS. The results of long-term corrosion test showed that the SZC could provide long-term protection in neutral 3.5 wt% NaCl solution for NdFeB magnet.

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“…The Nd‐phase in the magnet drastically accelerates the corrosion process and in turn greatly deteriorates the magnetic properties of NdFeB. To improve the corrosion resistance of NdFeB permanent magnets, lots of attempts have been developed such as the addition of alloying elements 3–5 and surface coatings 6–11.…”

Section: Introductionmentioning

confidence: 99%