Electroless Ni-P/Ni-B duplex coatings for improving the hardness and the corrosion resistance of AZ91D magnesium alloy

Zhang, W.X.; Jiang, Zhong Hao; Li, G.Y.; Jiang, Qing; Lian, Jainshe

doi:10.1016/j.apsusc.2008.01.144

Cited by 99 publications

(48 citation statements)

References 27 publications

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“…This process can effectively and economically improve the surface property and corrosion resistance of iron and steel products because of its high wear and corrosion resistance, good lubricity, and excellent thickness uniformity even in recessed areas [2][3][4][5][6][7][8][9][10]. In contrast to zinc or cadmium coatings that act as sacrificial coatings [11], Ni-P coatings function as a barrier by isolating the substrate from the aggressive environment. The coatings are cathodic to the substrate (steel) because the corrosion potential E corr is higher than that of the substrate.…”

Section: Introductionmentioning

confidence: 99%

Corrosion Resistance Of Electroless Ni-P/Cu/Ni-P Multilayer Coatings

Zhao

Zou

Hao

et al. 2015

Archives of Metallurgy and Materials

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coatings were prepared by deposition of Cu layer between two Ni-P layers. The Cu layer was deposited by metal displacement reaction between Cu 2+ and Fe atoms. Corrosion behavior of single-layer Ni-P coatings, double-layer Ni-P/Cu coatings, and three-layer Ni-P/Cu/Ni-P coatings were investigated by electrochemical tests in 3.5% NaCl solution. The three-layer coatings exhibited more positive E corr and decreased I corr compared with conventional single-layer Ni-P coatings, which indicated an improved corrosion resistance. The polarization curves of the three-layer coatings were characterized by two passive regions. The improved corrosion resistance was not only attributed to the function of the blocked pores of Cu. The Cu interlayer also acted as a sacrificial layer instead of a barrier in the coatings, which altered the corrosion mechanism and further improved the corrosion resistance of the coatings.Keywords: electroless plating, multilayer coatings, porosity, electrochemical tests, crystalline Cu layerWielowarstwowe powłoki Ni-P/Cu/Ni-P wytworzono metodą osadzania miedzi pomiędzy dwoma warstwami Ni-P. Warstwę Cu otrzymano dzięki reakcji wypierania metalu przez metal (dla miedzi i żelaza). Aby określić właściwości korozyjne jednowarstwowej powłoki Ni-P, dwuwarstwowej Ni-P/Cu oraz trójwarstwowej Ni-P/Cu/Ni-P przeprowadzono pomiary elektrochemiczne w 3,5% roztworze NaCl. Powłoki trójwarstwowe w porównaniu do jednowarstwowych wykazały się większą wartością E corr , przy malejącej wartości I corr . Wskazuje to na poprawę odporności na korozję. Krzywe polaryzacji dla powłok trójwarstwowych charakteryzują się występowaniem dwóch obszarów pasywacji. Poprawa odporności na korozję jest skutkiem nie tylko tzw. zjawiska blokowania porów w miedzi. Powłoka z Cu działała także jako warstwa protektorowa, modyfikując mechanizm korozji i poprawiając odporność korozyjną powłok.

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Section: Introductionmentioning

confidence: 99%

Corrosion Resistance Of Electroless Ni-P/Cu/Ni-P Multilayer Coatings

Zhao

Zou

Hao

et al. 2015

Archives of Metallurgy and Materials

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“…Electroless nickel phosphorous (NiP) is a well established autocatalytic chemical technique has the advantage of providing uniform coating thickness on a surfaces of metals [6], alloys [7] and plastics [8]. Binary NiP alloy coating is obtained using sodium hypophosphite as reducing agent and without the use of electricity.…”

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confidence: 99%

Influence of Nano Al2O3 Particles on the Adhesion, Hardness and Wear Resistance of Electroless NiP Coatings

Karthikeyan¹,

Vijayaraghavan²

2015

IJMMM

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Abstract-In this present study electroless NiP coatings and NiP-Al 2 O 3 coatings had been deposited on a mild steel substrate. The surface morphology of both the coatings had studied using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction technique. Adhesion, hardness and wear behavior were investigated and compared for NiP and NiP-Al 2 O 3 coatings. Optical micrograph images were used for the evaluation of adhesion of coatings which found sufficient and acceptable according to VDI 3198 standard. Hardness of the coating had been evaluated based on depth sensing techniques and substrate effect had avoided by maintaining depth to coating thickness ratio less than 0.1. Due to co-deposition of Al 2 O 3 particles the hardness of NiP coatings increased by 20.5% (7.8 GPa to 9.4 GPa). Dry sliding wear tests were conducted on PLINT TE66 micro scale tester against steel ball of hardness 800 HV. Wear resistance of NiP coatings increased with increase in sliding distance. The co-deposition of Al 2 O 3 particles in NiP matrix arrest the deformation during sliding of steel ball and thus wear resistance of NiP-Al 2 O 3 coatings is superior to NiP coatings. Wear crater morphology were studied using SEM and EDS. Adhesive wear mechanics was observed in NiP coatings and combination of adhesive and abrasive wear mechanism were found in NiP-Al 2 O 3 coatings.

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“…Always use non chlorinated, non-filmforming cleaning agents and solvents to clean and dry it. Steel (ferromagnetic) specimens having residual magnetism should be demagnetized for better results [20]. Report the methods used for cleaning and insert the disk securely in the holding device so that the disk is fixed perpendicular (61°) to the axis of the resolution.…”

Section: 2wear Testmentioning

confidence: 99%