化學(xué)專業(yè)外文翻譯--碳化鉻氧化物鍍層（英文）

1、Electrodeposition of mixed chromium metal-carbide-oxide coatings from a trivalent chromium-formate electrolyte without a buffering agentJ.H.O.J. Wijenberg a,*, M. Steegh a, M.P. Aarnts a, K.R. Lammers a, J.M.C. Mol ba Ta

2、ta Steel, Research & Development, IJmuiden Technology Centre, P.O. Box 10.000, 1970CA, IJmuiden, the Netherlands b Delft University of Technology, Department of Materials Science and Engineering, Mekelweg 2, 2628CD D

3、elft, the NetherlandsA R T I C L E I N F OArticle history:Received 19 March 2015Received in revised form 20 May 2015Accepted 21 May 2015Available online 23 May 2015Keywords:electrodepositiontrivalent chromiumelectrolyti

4、c chromium coated steelcurrent densitymass fluxA B S T R A C TThe electrodeposition of mixed chromium metal-carbide-oxide coatings on low carbon mild steel from atrivalent chromium-formate electrolyte without a buffering

5、 agent is investigated at a rotating cylinderelectrode enabling precise control of the mass flux.At equilibrium conditions, i.e. in the bulk of the electrolyte with pH 2.3, Cr(III) mainly exists in the formof [Cr(HCOO)(H

6、2O)5]2+. A deposition mechanism is proposed based on a fast, stepwise deprotonation ofthe water ligands in the Cr(III)-complex ion induced by a surface pH increase due to the hydrogenevolution reaction, which is controll

7、ed via the applied current density. Three different regimes can bedefined related to the current density and mass flux.At low current densities no deposit is formed on the electrode, because soluble [Cr(HCOO)(OH)(H2O)4]+

8、is formed at the electrode (regime I). Above a certain threshold value of the current density Cr(HCOO)(OH)2(H2O)3 is deposited on the electrode (regime II). A part of the Cr(III) of the deposit is reduced to Cr-metal and

9、 formate is broken down leading to the formation of Cr-carbide. The amount and composition ofthe deposit in regime II strongly depend on the applied current density, mass flux and electrolysis time. Athigh current densit

10、ies, a further shift of the acid-base equilibrium to [Cr(HCOO)(OH)3(H2O)2]? results in adeposit on the electrode that is mainly composed of Cr-oxide (regime III). In stark contrast to regime II,the amount and composition

11、 of the deposit in regime III are almost invariant of the applied currentdensity, mass flux and electrolysis time.ã2015 Elsevier Ltd. All rights reserved.1. IntroductionChromium coatings are widely used for many dif

12、ferent applications, including Electrolytic Chromium Coated Steel (ECCS) for packaging applications [1–3]. ECCS consists of a thin gauge low carbon steel substrate with a very thin coating comprising a base layer of chro

13、mium metal (50–150 mg m-2) and a top layer of chromium oxide (7–35 mg m-2). ECCS is produced in high-speed continuous steel strip plating lines, in which an endless steel strip of about 1 m wide is transported very fast

14、(typically > 5 m s?1) through one or more plating cells. The fast movement of the steel strip induces a lot of turbulence resulting in a high mass transfer rate of the electro-active species. A high mass transfer rate

15、 allowsthe application of very high current densities. Typically, the deposition process is already completed within a few seconds. ECCS is produced from hexavalent chromium electrolytes. But Cr(VI) is nowadays considere

16、d a hazardous substance that is harmful to the environment and constitutes a risk in terms of worker safety. The use of Cr(VI) will be restricted within Europe in 2017 due to REACH legislation [4]. Research in the past d

17、ecades has focussed on the development of trivalent chromium electrolytes since Cr(III) compounds are not toxic [5–19]. Commercial Cr(III) plating processes for applying decorative coatings have already been in use since

18、 the mid-1970s [5]. Such electrolytes typically contain a complexing agent (e.g. formate, acetate, oxalate, citrate or glycine) for destabilising the very stableCrðH2OÞ3þ 6 complex and a pH buffer (usually

19、 boric acid) forpreventing hydrolysis and olation reactions by minimising the pH increase near the cathode as a result of hydrogen formation [6–8]. Further details of the hydrolysis, olation, polymerisation and* Correspo

20、nding author at: Tata Steel, Research & Development, IJmuidenTechnology Centre, P.O. Box 10.000, 1970CA IJmuiden, the Netherlands. Tel.: +31 0251 498714E-mail address: jacques.wijenberg@tatasteel.com (J.H.O.J. Wijenb

21、erg).http://dx.doi.org/10.1016/j.electacta.2015.05.1210013-4686/ã 2015 Elsevier Ltd. All rights reserved.Electrochimica Acta 173 (2015) 819–826Contents lists available at ScienceDirectElectrochimica Actajourna l hom

22、e page : www.e lsevier.com/loca te/ele cta ctato a cylindrical shape and welded on a Soudronic AFB 1000 can body welder. The height of the cylinders was 113 mm. The large surface area of the steel cylinders (2.6 dm2) fac

23、ilitates surface analysis. A platinised Ti cylinder custom-made by MAGNETO special anodes B.V. with an inner diameter of 100 mm served as counter electrode. The thickness of the titanium is 2 mm and the platinum coating

24、 weight is 50 g m?2. The anode was symmetrically positioned with respect to the steel cylinder. The anode was partially isolated by means of a plastic insert. The primary current density was optimised such that the

25、 local current density over the cylinder is exactly equal to the applied current density for almost its entire surface area except for both edges. The primary current distribution over the steel cylinder was calculated w

26、ith the software package ElSy Version 6.1. For calculating the primary current distribution, two differential equations were solved numerically for this cell geometry: theLaplace equation (r2f ¼ 0) and Ohm's law

27、 (i ¼ ?krf), where f is the potential [V], i the current density [A m?2] and k the electrolyte conductivity [S m?1]. The actual current density at the centre of the steel cylinder is exactly equal to the applied cur

28、rent density when the active height of the anode is 103 mm. In Fig. 1, the primary current distribution over the steel cylinder is shown from its centre (x = 0) to its edges (x = 0.5 h). The maximum rotational speed (V)

29、of the RCE device is about 15 RPS (Revolutions Per Second) corresponding to V0.7 = 6.7 s?0.7due to the onset of a vortex at higher rotational speeds. Because the mass flux at an RCE is directly proportional to the rotati

30、onal speed to the power 0.7 [27], V0.7 was increased stepwise from 1 to 6 s?0.7. A programmable AXA (Axel Åkerman) fast timing Pulse Plating Rectifier (? 48 VDC, ? 500 A) was used for applying the current.2.4. Surfa

31、ce analysis2.4.1. XRF The total amount of chromium was measured with a SPECTRO XEPOS XRF (X-Ray Fluorescence) Spectrometer. This instrument has a sample tray with 8 positions for circular samples with adiameter of 40 mm.

32、 The reported XRF values are corrected for the contribution of the steel substrate to the Cr signal.2.4.2. XPS X-ray Photoelectron Spectroscopy (XPS) spectra and depth profiles were recorded on a Kratos Axis Ultra using

33、monochro- mated Al Ka X-rays of 1486.6 eV. The measured spot size was 700 mm ? 300 mm. The depth profiles were recorded using 4 keV Ar+ ions creating a sputter crater of 3 mm ? 3 mm. The sputter rate was calibrated with

34、the XRF results and was 1.59 nm min?1.2.4.3. FEG SEM The surface morphology of the samples has been characterised with a Zeiss Ultra 55 FEG SEM (Field Emission Gun - Scanning Electron Microscope). For optimal image resol

35、ution on the outer surface of the samples, a low acceleration voltage of 2 kV was used in combination with a short working distance and small aperture. For obtaining chemical information, EDX analysis was performed with

36、a standard acceleration voltage of 15 kV, standard working distance and aperture. These settings resulted in a dead time between 30–35 %. For all samples an average EDX spectrum was collected on an area of 1000 mm ? 750

37、mm for 50 s.3. Results and discussion3.1. Effect of applied current density on coating weightIn Fig. 2, the Cr coating weight as measured with XRF is plotted as a function of the current density at a fixed rotational spe

38、ed ofFig. 1. Primary current distribution over the steel cylinder from its centre (x = 0) to its edge (x = 0.5 h) for the shown geometry.01002003004000 10 20 30 40 50 60 70 80 90i / A dm-2Cr (XRF) / mg m-2regime

39、I regimeII regimeIIIFig. 2. Cr coating weight vs. current density showing the 3 different depositionregimes (V0.7 = 5 s?0.7, t = 1 s).Table 2Cr(III) electrolyte composition.compound formula concentration (g l?1)basic c