Corrosion resistance of electrodeposited Ni–Al composite coatings on the aluminum substrate
Corrosion resistance of electrodeposited Ni–Al composite coatings on the aluminum substrate
S.Ghanbari a ,1,F.Mahboubi b ,?
a Department of Materials Engineering,Islamic Azad University Science and Research Branch,Tehran,Iran
b
Department of Mining &Metallurgical Engineering and Advanced Technologies Research Center,Amirkabir University of Technology,Tehran,Iran
a r t i c l e i n f o Article history:
Received 19July 2010
Accepted 7December 2010
Available online 16December 2010Keywords:C.Coatings E.Corrosion I.Adhesion
a b s t r a c t
Ni matrix–Al particle composite coating was adopted via sediment co-deposition (SCD)method on the zincate coated aluminum substrate.Surface morphology was investigated by scanning electron micros-copy (SEM).The electrochemical behavior of the coatings was studied by polarization potentiodynamic test in 3.5wt.%sodium chloride using a three electrode open cell.The effect of the electroplating param-eters on the Al co-deposition was studied.Maximum of 22wt.%Al particles were deposited in the coat-ing.It was found that the zincate coating plays an important role in improving the nickel layer adherent.Furthermore,incorporation of aluminum particles in Ni matrix re?ned the Ni crystal coatings.However,polarization curves shifted to negative potentials and corrosion rate is decreased.
ó2010Elsevier Ltd.All rights reserved.
1.Introduction
Surface modi?cations of aluminum and its alloys can offer a wide variety of mechanical,chemical,electrical properties and dec-orative ?nishing.Electroplating has gained commercial applica-tions for components which need to wear and corrosion resistance.Especially,some kinds of plating methods dispersing ceramics particles in metallic matrixes are becoming popular in various wear parts [1].
The electro deposition of metallic coatings containing inert par-ticles can be traced back to studies which produced a graphite–cop-per composite coating for self-lubricating surfaces in car engines [2].In the early 1950s and late 1960s,the development of electro depos-it composite coatings developed gradually [3,4].During the 1970s and 1980s,investigations were focused on the necessity of produc-ing coatings with enhanced mechanical and corrosion properties.To this end,irresolvable particles are suspended in a common plating electrolyte and are captured in the growing metal layer.These par-ticle can be hard oxides or carbides such as ZrO 2,WC [5],Al 2O 3[6]and SiC [7,8].Foster suggested that the oxidation resistant coatings could be prepared by co-electrodepositing of metal,for example Ni,with micrometer-sized metallic particles such as Cr [8].Ni–Al com-posites were prepared by the co-deposition of a Ni matrix and mi-cron sized Al particles by Susan [9,10].
Two common processes involved with incorporation of particles into metallic coatings can be recognized,namely,physical disper-sion of particles in the electrolyte and electrophoretic migration of particles [11].Many theories have been suggested including the transport of particles due to electrophoresis.The mechanism proposed by Guglielmi [5,12]had been adopted by several authors.This model enables a quantitative treatment of the in?uence of particles concentration and current density on the incorporation rate of particles into a metal deposit and excludes hydrodynamic effects and particle characteristics.The common processes in-volved in the co-deposition of particles into growing metallic lay-ers.Five steps during the co-deposition process can be identi?ed:(1)Formation of ionic clouds on the particles,(2)convection to-wards the cathode,(3)diffusion through a hydrodynamic bound-ary layer,(4)diffusion through a concentration boundary layer,and (5)Adsorption at the cathode,where particles are entrapped within the metal deposit [13].
Surface oxide ?lm of aluminum and the extreme reactivity of bare aluminum result in rapid re-formation of the ?lm on exposure to air or aqueous solutions,which cause the dif?culty of plating on aluminum substrate [14].Other problems for Ni coating on alumi-num are:
(1)In?uence of electrochemical potential.The electrochemical
positions of aluminum and nickel in metal series have a pro-found in?uence on deposition reactions and adhesion,mak-ing the plating quite dif?cult [15].The electrochemical potential of Ni and Al metal are shown in Table 1[11].
(2)Effects of the coef?cient of thermal expansion on bond
strength.The expansion coef?cient of aluminum and its alloys are quite different from that of the nickel.In applica-tions,where considerable temperature changes occur,the different expansion of aluminum and the deposited metal
0261-3069/$-see front matter ó2010Elsevier Ltd.All rights reserved.doi:10.1016/j.matdes.2010.12.020
?Corresponding author.Tel.:+982164542967.
E-mail addresses:ghanbari.siavash@https://www.sodocs.net/doc/c918240817.html, (S.Ghanbari),mahboubi@aut.ac.ir (F.Mahboubi).1
Tel.:+982144220940.
?lm may cause suf?cient strain to rupture the bond between the deposit and the substrate metal [11].
(3)Effects of the differences in atomic diameter and crystal lat-tice structure between the aluminum substrate and nickel [12].
(4)Effects of aluminum oxide ?lm which has amphoteric nature
and cause complicating reaction on surface during the prep-aration process for plating [12].Weak adherence on the aluminum substrate can be only im-proved by heating treatment in order to increase the speed of pla-ted metals diffusion into the aluminum substrate.Furthermore,the adhesion problem is solved by zincate processes [3].Precise con-trol of the solution and operating condition are very important to create uniform and ?rmly adherent layer of zinc ?lm and ulti-mately attain high adhesion strength of plated deposits on aluminum.
The aims of the present work were to produce Ni–Al composite
Phase characterization of the coating was investigated by X-ray diffraction (XRD)using SEIFERT 3003PTS PC type with Cu K a radi-ation at a voltage of 20kV.The surface morphologies and elemen-tal analysis of the samples were investigated using a LEO 440i scanning electron microscope equipped with an energy dispersive X-ray analysis (SEM/EDS)and an Olympus optical microscope (OM).Polarization studies were carried out in 3.5wt.%NaCl solu-tions at the room temperature (25°C),by using a potentiostat EG&G system.Potentiodynamic anodic polarization curves were established.The specimen was used as a working electrode,coun-ter electrode was platinum and the reference electrode was satu-rated calomel electrode (SCE).Before running the corrosion test,the specimens were cleaned with acetone,and then rinsed in deionized water.The samples were polarized from à800mV to +900mV versus open circuit potential (OCP).Table 1
The Ni and Al parameters [11].
Potential Structure Lattice A.Diameter Valance Solution Ni à0.07fcc 3.517 2.48720.005Ai
à0.85
fcc
4.0413
2.875
3
–
Table 2
The composition of Watts type nickel solution.
Composition of nicke solution Operating conditions Nickel chloride (NiCl 2_6H 2O):45g/l Current density:2–9A/dm 2Nickel sulfate (NiSO 4_6H 2O):300g/l Temperature:45–50°C
Boric acid (H 3BO 3):30g/l
Magnetic stir rate:150rpm Sodium dodecyl sulphate:0.1g/l –Particle:pure A1particles,5l m
–
1860
S.Ghanbari,F.Mahboubi /Materials and Design 32(2011)1859–1864
deposition arises through two continual steps:?rst,particles adsorbing metal ions are loosely adsorbed on cathode,and then the reduction of ions provides strong adsorption between particles and cathode [5].
In Eq.(1),as concentration of powder (C )and its embedded frac-tion (a )are related mathematically
a ?eMi 0T=enF q m T?exp eA àB Tg eK à1tC T
where F is the Faraday constant,q m is the density of electrode-posited metal,g is the over potential of the electrode reaction,M the atomic weight of the electrodeposited metal,i 0is the exchang-
4.Variation of weight percentage of Al particles in coating with volume fraction of Al particles in solution.
Fig.5.EDS of sample coated with Ni–22wt.%Al,in 9A/dm 2.
Fig.6.Effect of the magnet stir rate on the Ni–Al composite coating (24g/l Al).
ing current density,n is the valence of the electrodeposited metal, and k is the Langmuir isotherm constant,mainly determined by the intensity of interaction between particles and cathode.The param-eters t0and B are related to particle deposition,and both play a po-lar role with parameters i0and A related to metal deposition.The Constants A and B can be seen as the total charge passing through the electrode interface and carried by Ni2+ions and compassed Al during the reaction[5].The obtained curve in Fig.3is quite similar to the Langmuir adsorption isotherms,supporting a mechanism based on an adsorption effect.
The?rst step is nominated loose adsorption,where particles have loose physical adsorption on the cathode with metal ion cov-erage.In this step,there is a layer of adsorbed ions and solvent molecules have interaction between the electrode and the parti-cles.The second is a strong adsorption step,which is electrochem-ical reaction produces a strong adsorption of powders onto the electrode.
Fig.5shows EDS analysis that revealed Ni–Al composite coat-ings.This coating contains22wt.%Al that resulted from32g/l Al suspended in solution.This trend was similar to other neutral par-ticles composite coating systems including Ni–La2O3[16],Ni–Al2O3 [17]and Ni–PTFE[18].
3.2.Magnetic stirrer
Weight percentage of Al particles in coating depends on mag-netic stirrer rate.As it shown in Fig.6,the amount of Al particles in region(I)increased with increasing of magnetic stirrer rate, and the porosity is seen to be insensitive,but in region(II)porosity is enhanced and Al particles in coating are observed to be de-creased.According to Fig.7,agitation has an optimum range for high concentration of Al particles in coating.
3.3.Current density and temperature
Current density is a one of the important factor[19,20].Com-posite coating was prepared from5up to11A/dm2with aluminum concentration of8,16,24,32g/l in solution.The effect of the cur-rent density on the wt.%of the Al is shown in Fig.8.Al concentra-tion in coating is enhanced with increasing in the current density up to9A/dm2.Enhancing the current density more than11A/ dm2causes to stabilize of Al concentration in the coating.
As shown in Fig9.With increasing in the temperature of the coating bath from40to50°C,the Al content of the coating is in-creased.Further rising in the temperature(55°C)resulted in a de-crease in the amount of Al in the coating.
3.4.X-ray diffraction analysis(XRD)
Fig.10shows the XRD pattern of three samples of pure nickel coating,composite coating(Ni–Al)and zincate coating,obtained at a current density of9A/dm2.This analysis is very important for the zincate sample in order to increase the adherence of nickel on the aluminum surface.As shown in Fig.10for preventing the aluminum oxide formation on the surface,copper oxide and zinc oxide phases should be formed therefore nickel adhesion on the aluminum substrate will be increased.The average grain sizes of the coatings were calculated from the diffraction peak widths (Scherrer equation),according to:
s?0:9k=eB cos hTe2Twhere0.9is the shape factor,k is the X-ray wavelength,B is the line broadening at half the maximum intensity(FWHM)in radians,and h is the Bragg angle,s is the mean size of the ordered(crystalline) domains.In the composite coating of Ni–16wt.%Al the mean size of the nickel crystallites are calculated to be14.4nm.
3.5.The micro Vickers hardness of the composite coatings
The hardness of the electrodeposition composite coating de-pends on many factors(e.g.current density,particle concentra-tion).Micro hardness of Ni–Al composite coatings with8,16,24, and32g/l Al are320,340,370,and480HV,https://www.sodocs.net/doc/c918240817.html,par-atively the hardness of these composite coatings is higher than that of pure nickel plating;hardness of pure nickel was230HV.The improvement in the hardness of Ni–Al composite coatings can be
Fig.9.Effect of the temperature on the wt.%of Al in the coatings.
and Design32(2011)1859–1864
https://www.sodocs.net/doc/c918240817.html,parative polarization potentiodynamic curves for Ni–Al composite coating in3.5wt.%sodium chloride solutions obtained after40min of immersion time.
Fig.12.Typical SE picture of SCD Ni–Al composite coating32g/l Al in solution. explained on the basis of increasing the current density or particle concentration in the solution that increase the amount of the alu-minum particle in the coating.On the other hand,the microstruc-ture of the nickel coating is changed due to the presence of the aluminum particles in the coating[10].The uniformly distributed aluminum particulates in the Ni matrix could prevent the growth the Ni grains and avoid the plastic deformation of the coating under loading.
parameters had effected on the amount of Al particle deposits.Al metal particles shifted polarization curves to negative potentials and corrosion rate is decreased.Deposition of Al particles could be explained by the Guglielmi’s model for inert particles.
Acknowledgements
The authors would like to thank the Surface Engineering labora-tory of the science and research center of Azad University and Sur-face Engineering laboratory of Amirkabir University of Technology. References
[1]Cui Xinwei,Wei Weifeng,Liu Haifeng,Chen Weixing.Electrochemical study of
co-deposition of Al particle nanocrystalline Ni/Cu composite coatings.
Electrochimica Acta2008;54:415–20.
[2]Low CCTJ,Wills RGA,Walsh FC.Electrodeposition of composite coatings
containing nanoparticles in a metal deposit.Surf Coat Technol 2006;201:371–83.
[3]Ram DS,Sudhir K.Study of the effects of surfactants on the electrodeposition of
Ni–Co Alloy.Surf Coat Technol1980;5:343–8.
[4]Garcia I,Conde A,Langelaan G,Celis JP.Improved corrosion resistance through
microstructural modi?cations induced by codepositing SiC-particles with electrolytic nickel.Corr Sci2003;45:1173.
[5]Guglielmi N.Kinetics of the deposition of inert particles from electrolytic
baths.J Electrochem1972;119:1009.
[6]Verelst M,Bonino JP,Rousset A.Electroforming of metal matrix composite
dispersoid grain size dependence of thermostructural,mechanical properties.
Mater Sci Eng1991;135:51.
[7]Feng Qiuyuan,Li Tingju,Yue Hongyun,Qi Kai,Bai Fudong,Junze Jin.
Preparation and characterization of nickel nano-Al2O3composite coatings by sediment co-deposition.Applied Surf Sci2008;254:2262–8.
[8]Sheng Chang W,Wen Cheng JW.Kinetics of electroplating process of nano
sized ceramic particle/Ni composite.Mater Chem Phys2003;78:573–80. [9]Susan DF,Marder AI.Electrodeposited Ni–Al particle composite coatings.Oxid
Met2002;57:159.[10]Vitry V,Delaunois F,Dumortier C.Mechanical properties and scratch test
resistance of nickel–boron coated aluminium alloy after heat treatments.Surf Coat Technol2008;202:3316–24.
[11]Yang X,Peng Y,Wang F.Effect of annealing treatment on the oxidation of an
electrodeposited alumina-forming Ni–Al nanocomposite.Corr Sci 2008;50:3227–32.
[12]Wu Gang,Li Ning,Wang Dian Long,Zhou De Rui,Xu Bo Qing,Mitsuo Kurachi.
Effect of a-Al2O3particles on the electrochemical co-deposition of Co–Ni alloys from sulfamate electrolytes.Mater Chem Phys2004;87:411–9.
[13]Liu Haifeng,Chen Weixing.Reactive oxide-dispersed Ni3Al intermetallic
coatings by sediment co-deposition.Intermetallics2005;13:805–17.
[14]Bund Andreas,Thiemig Denny.In?uence of bath composition and pH on the
electrocodeposition of alumina nanoparticles and nickel.Surf Coat Technol 2007;201:7092–9.
[15]Adolphe F,Anton H,Wieland S.Template electrochemical deposition and
characterization of zinc–nickel alloy nanomaterial.Electroa Chemist 2007;604:137–43.
[16]Narayan Raj,Chattopadhyay S.Electrodeposited Cr–Al2O3composite coatings.
Surf coat Technol1982;3:227–34.
[17]Peipmann R,Thomas J,Bund A.Electrocodeposition of nickel–alumina
nanocomposite?lms under the in?uence of static magnetic?elds.
Electrochim Acta2007;52:5808–14.
[18]Brenner A.Electrodeposition of alloys,vol.II.New York:Academic Press;1963.
[19]Shia L,Suna CF,Zhoua F,Liu WM.Electrodeposited nickel–cobalt composite
coating containing nano-sized Si3N4.Mater Sci2005;397:190–4.
[20]Feng Qiuyuan,Li Tingju,Yue Hongyun,Qi Kai,Bai Fudong,Jin Junze.
Preparation and characterization of nickel nano-Al2O3composite coatings by sediment co-deposition.Appl Surf Sci2008;8:2262–8.
[21]Bercot P,Pena-Munoz E,Pagetti J.Electrolytic composite Ni–PTFE coatings an
adaptation of Guglielmi’s model for the phenomena of incorporation.Surf Coat Technol2002;157:288–9.
[22]Alimadadi H,Ahmadi M,Aliofkhazraei M,Younesi SR.Corrosion properties of
electrodeposited nanocrystalline and amorphous patterned Ni–W alloy.Mater Des2009;30:1356–61.
[23]Walsh FC,Ponce de León,Kerr C,Court S,Barker BD.Electrochemical
characterisation of the porosity and corrosion resistance of electrochemically deposited metal coatings.Surf Coat Technol2008;202:5092–102.
[24]American society for testing and materials.ASTM B-571-97standard methods
for adhesion of metallic coatings.Philadelphia:ASTM;2003.
1864S.Ghanbari,F.Mahboubi/Materials and Design32(2011)1859–1864