ADVANCED CHARACTERIZATION METHODS FOR NICKEL AND ZINC-NICKEL ALLOY LAYERS ELECTROCHEMICALLY DEPOSITED


Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava  
Volume X,  Issue 4 - 2011 

 
 

89 
 

ADVANCED CHARACTERIZATION METHODS FOR NICKEL AND ZINC-
NICKEL ALLOY LAYERS ELECTROCHEMICALLY DEPOSITED 

 
*Violeta VASILACHE  

 
Stefan cel Mare University of Suceava, Faculty of Food Engineering. 13 th University Street, 720229, Romania, 

E-mail adress: violetav@usv.ro 
*Corresponding author 

Received 12 August 2011, accepted 5 November  2011 
 
 

Abstract. Nickel and zinc-nickel alloys were electrochemically deposited. The layers were studied with 
scanning electron microscope (SEM), composition was revealed through studies of energy dispersive 
of X-rays (EDX) and X-ray diffraction (XRD), the reflectance was studied by reflectance spectroscopy 
and the hardness with a Vickers indenter device. Nickel electroplating has a great commercial 
and industrial importance and offers a very good quality finish of surfaces. This importance is 
emphasized by increasing of annual global consumption of nickel, which goes to 100.000 
tones. The applications of electroplating could be derived in three categories: decorative, 
functional and electroforming. In ordinary coating the zinc remains the principal metal for 
industrial applications, especially for coverage of steel products. In the last two decades it 
was registered an important increasing of application of electrodeposited alloys due to the 
market demand for products with high quality coatings. On the first place there are the 
machine buildings industry and the aerospace industry, also those for electrical components 
and for fixing devices. Because of fact that consumption of heavy metals has to be reduced 
year by year, until the total elimination, there are searching for new technologies and one of 
the most promised of them is that of alloys electrochemical coatings with Zn-Ni, Zn-Co and 
Zn-Fe. 
 
Keywords: Nickel, Zinc-Nickel alloys, SEM, EDX, and XRD techniques, reflectance, Vickers 
hardness 
 
 

 

1. Introduction 
 

Nickel electroplating has a great 
commercial and industrial importance and 
offers a very good quality finish of 
surfaces. This importance is emphasized 
by increasing of annual global 
consumption of nickel, which goes to 
100.000 tones. The applications of 
electroplating could be derived in three 
categories: decorative, functional and 
electroforming. 
In ordinary coating the zinc remains the 
principal metal for industrial applications, 
especially for coverage of steel products. 
In the last two decades it was registered an 
important increasing of application of 
electrodeposited alloys due to the market 

demand for products with high quality 
coatings. On the first place there are the 
machine buildings industry and the 
aerospace industry, also those for electrical 
components and for fixing devices. 
Because of fact that consumption of heavy 
metals has to be reduced year by year, until 
the total elimination, there are searching 
for new technologies and one of  
the most promised of them is that of alloys  
electrochemical coatings with Zn-Ni, Zn-
Co and Zn-Fe.[1,2,3] 
The greatest automobile companies are in a 
continuous course for prolonging the 
warranty period, so their products are 
better and better year by year. The majority 
of the European factories have been 
changed the specifications regard the 

mailto:violetav@usv.ro


Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava  
Volume X,  Issue 4 - 2011 

 
 

90 
 

improvement of the performances of the 
electrodeposited layer.  
Those new economic politics are based just 
on the using of alloys like Zn-Ni, Zn-Co 
and Zn-Fe [4,5,6,7]. 
Out of the machine building industry there 
are interesting in the using of 
electrodeposited alloys in the field of 
industry for defense. The State Department 
of USA is asking for eliminate during the 
follow years of the old technologies with 
new technologies based on the zinc-nickel 
alloys [11,12,13,16]. 
 
2. Experimental  

  
Electrodeposition of nickel was performed 
at INCDFM Bucharest-Magurele Institute, 
in the Electrochemistry Department. A 
Watts bath was used, having the 
composition: NiSO4.6H2O, 120g/l; 
NiCl2.6H2O, 35g/l şi H3BO3, 35g/l. We 
worked at different temperatures (40-
60°C). The experimental device used to 
realize nickel deposition is composed by a 
potentiostat-galvanostat VoltaLab 40 
including VoltaMaster 4 software, a 
thermostated electrolyze cell with a 
thermostate Lauda 003, magnetic shaker 
and thermometer to control temperature. 
As reference electrode it was used calomel 
electrode and the contra-electrode was 
made by electrolytic nickel. The work 
mode respected the next steps in the 
designing of the experiments. Primary the 
plates of copper were cut and the thickness 
was measured with micrometer. Then it 
followed a mechanical processing of the 
surfaces (like polish) with emery paper and 
with felt. The solutions were prepared 
following the recipe described as above 
mentioned (Merk reactive substances were 
used). The copper plates were degreased 
with chloride acid (5%, temperature 65C), 
washed, dried and weighing. 
Before proceeds to depose nickel there 
were drawn the polarization curves to 
establish the range of values for 

discharging of ions in solution. During the 
deposition there were recorded the values 
for current density. 
The electrochemical reactions on the 
cathode could be written generally: 

Ni2+ + 2e- → Ni,  (1) 
but the proposed mechanism is by next 
type: 

Ni2+ + H2O → (NiOH)+ + H+  (2) 
(NiOH)+ + e- → (NiOH)ads (3) 

(NiOH)ads + (NiOH)+ + 3e- → 2Ni + 2OH- 
(4) 

This mechanism was proposed after the 
study of inductive impedance loops with 
the method of electrochemical impedance 
spectroscopy, but all steps was not 
identified and elucidate yet. 
The anomalous co-deposition of thin films 
of zinc-nickel alloys was performed 
electrochemically. In the way to obtain the 
desired properties it was necessary to 
search the influence of electrodeposition 
conditions (co-deposition potential, the 
bath’s composition, the temperature for 

deposition, mechanical stirring) through 
the structure, morphology, composition 
and optical properties, transport properties 
and magnetic properties of layers. 
The next recipes were used to prepare the 
low acid electrolyte for electrodeposition 
of zinc-nickel alloys: 
The first solution: zinc chloride 130g/l, 
nickel chloride 130g/l, potassium chloride 
230g/l, pH 5-6, t(°C) 24-30°C; 
The second solution: zinc chloride 130g/l, 
nickel chloride 65g/l, potassium chloride 
230g/l, pH 5-6, t(°C) 24-30°C. 
As working electrode it was used a glass 
plate with a deposed gold layer, made by 
sputtering method (a Hummer 6 
installation was used). The pH was 
maintained at a level between 5 and 6 
naturally without adding acids, because the 
salts used were chlorides which through 
electrolytic dissociation have acid 
character (excepting KCl, which comes 
from a strong acid and a strong base). The 
work temperature was between 24°C and 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava  
Volume X,  Issue 4 - 2011 

 
 

91 
 

30°C. As reference electrode it was used 
the calomel electrode directly immersed in 
the electrolyze cell. 
The chemical reactions which occur on the 
cathode follow two steps, as there were 
described by Matlosz. Zinc ions are 
deposited on their own substrate, on the 
gold substrate and on the nickel substrate. 
Also, nickel ions are deposited on their 
own substrate, on the used gold substrate 
and on the zinc substrate. In addition it has 
to take account the secondary reactions 
when ions Zn2+ combine with hydrogen to 
form ZnH+, in the same way ions Ni+ 
combine with hydrogen to form NiH+. 
These intermediate species, formed in the 
process of adsorption, will decompose 
finally to form metallic Zn and metallic Ni 
respectively. 
The electrochemical reactions which 
occur could be written as follow: 

Ni2+ + e- → Ni+ads   (5) 
Ni+ads + e- → Ni                 (6) 

Ni + H+ + → NiH+ads                   (7) 
NiH+ads + H+ + 2e- → Ni + H2 (8) 

Zn2+ + e- → Zn+ads       (9) 
Zn+ + e- → Zn    (10) 

Zn + H+ → ZnH+ads  (11) 
ZnH+ads + H+ + 2e- → Zn + H2   (12) 
Ni2+ and Zn2+ are dissolved as 

metallic ions, hydrolyzed or not. Ni+ads and 
Zn+ads which could or not to contain 
hydroxyl group are monovalent adsorbed 
in intermediate reactions. Ni and Zn are the 
metallic deposits of nickel and zinc 
respectively. 
 
3. Results and Discussion 

 
The nickel layers electrodeposited were 
analized at INCDFM Bucuresti-Magurele 
using scanning electron mycroscopy type 
Zeiss EVO 20. Figure 1 presents a SEM 
image of a sample of nickel 
electrodeposited at -700 mV potential, 
working temperature 65C. In the first 
image which has the resolution 10620X it 
can be observed the steps of electro-

crystallization, and also the micro-pores 
produced by hydrogen evolution. In the 
image having the resolution 58450X, it can 
be seen a micro-pore in the right-down-
corner. Both images present a uniform 
covered surface, a good quality of the 
deposited layer [14,15]. 
One set of measurements of the obtained 
samples are reflectance measurements. 
Brightness is a characteristic which 
depends by human eyes sensibility, so an 
objective physics parameter is reflectance.  
 

 
 
In order to measure this we used an Ocean 
Optics Spectrometer, doted with Spectra 
Suite soft, in Stefan cel Mare University, 
Suceava.   
The reflectance is defined as a percent 
(%Rλ) relatively on the reflectance of a 
standard reference suface: 

 

%100
DR
DS

R% ×
x 
x 

=
λλ

λλ

λ    (13)  

where Sλ- intensity of sample at light 
length λ; Dλ- darkness intensity at light 
length λ; Rλ- reference intensity at light 
length λ. The first necessary step when it 
has to do reflectance measurements 
(generally for all types of measurements) is 
calibration of devices. In our case we used 
a mirror from spectrometer auxiliaries and 
we chose the value 100%. For the next 
example we considered two samples of 
nickel electrodeposited on copper 

  
 

Figure 1. SEM images of the nickel electrodeposited layer from a 
Watts bath with addition of PVP at -700 mV potential, 65C 

temperature, deposition time 10 minutes, with magnetic shaking 
of the electrolyte (SEM-Zeiss EVO 20 device) 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava  
Volume X,  Issue 4 - 2011 

 
 

92 
 

substrate, both in the same conditions, 
excepting temperature, one of them 
performed at 45C and the other at 65C. 
As it could see, the reflectance for the 
lowest temperature is higher.  

 

 
 

Figure 2. Graph chart recorded for a sample of 
nickel electrodeposited on copper substrate at      
-900 mV potential, temperature 65C, time 2 

minutes 
 

For all samples of nickel electrodeposited 
on copper substrate at -900mV potential 
and temperatures from 45C to 65C, we 
measured reflectance for all visible 
domains. Corresponding to wave length of 
550 nm, we draw the next chart for 
dependence reflectance versus 
temperature: 

0

5

10

15

20

25

45 50 55 60 65

t(°C)

re
f%

 
Figure 3. Reflectance vs. Temperature 

These results are similar those obtained by 
other researchers and it is easy to see that 
the best reflectance (and brightness, of 
course) is obtained for the lowest 
temperature. For higher than 60C 
temperatures the brightness increases 
again, but economic efficiency of the 
process is lowest, because it is necessary to 
spend heat for increasing the temperature 
of the electrochemical cell. Another type 
of investigations we’ve made there were 

SEM-EDX analyzes performed on Al.I. 

Cuza University – Iasi.. The investigation 
was performed by means of a 
SEM   VEGA II LSH scanning electronic 
microscope manufactured by TESCAN for 
the Czech Republic, coupled with an 
EDX   QUANTAX QX2 detector 
manufactured by ROENTEC Germany. 
 

Table 1 
 Composition of a sample of nickel 

electrodeposited on copper substrate, from a 
Watts bath at -750mV potential, 60C, 

temperature, sodium lauryl-sulfate and 
saccharine agents added 
 

 

Element  [norm. wt.-%] [norm. at.-%] Error in % 
Nickel 72,98950 70,04394 1,95537 
Copper 24,72697 21,91705 0,687472 
Carbon 7,39E-09 3,47E-08 0,025 
Oxygen 2,283528 8,039002 0,535272 

 100 100  
 

 
Figure 4. EDX pattern for a nickel sample 

electrodeposited on copper substrate at -750 mV 
and 60ºC 

Analyzing the X-ray diffraction specter of 
a zinc-nickel alloy electrodeposited on 
gold substrate, there were found the next 
elements (table 2)  
The pick corresponding to (111) plane of 
nickel was found at an angle of 2=4436, 
and those corresponding to (111) plane of 
zinc at an angle of 2=3812. This 
analyze confirms too, the formation of 
zinc-nickel alloy. The deposited metals 
crystallize in cubic with centered faces. So, 
for nickel, the values for axes are (in 
Ångstrom) a=3,52380, b=3,52380 and 
c=3,52380 with all angles equals of 90, 
and for zinc the dimensions are 
a=b=c=2,4730, with the same angles of 
90. 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava  
Volume X,  Issue 4 - 2011 

 
 

93 
 

Table 2 
Identified elements after X-ray diffraction 

analyze for a sample of zinc-nickel alloy 
electrodeposited at -1100 mV potential and 30°C 

temperature 
Identified element dhkl (Å) Crystalin 

plane 
Zn CFC-2,4730 (111) 
Au CFC-4,07860 (222) 
KCl CFC-6,29170 (222) 

Zn5(OH)8Cl2.H2O Rombic-
6,3400;6,3400;23,6600 

(111) 

Ni CFC-3,52380 (111) 
Ni CFC-3,52380 (220) 

(Ni(OH)2)(NiOOH) Rombic-
3,0710;3,0710;23,2000 

(222) 

 

0 20 40 60 80 100
0

5

10

15

20

25

30

35

40

45

 solutia II

 solutia I

Int
en

sia
ta

te
a d

e d
ifr

ac
tie

(u
nit

.ar
b.)

2-Theta(grade)

200
111

200

111
220

003

111

200
311

222

Aliaje Zn-Ni-P2P4

 
Figure 5. X-ray diffractogramme recorded for a 

Zn-Ni alloy co-deposited on gold substrate a) 
from solution I, b) form solution II 

 
Another type of measurements was those 
of micro-hardness. The experiments were 
performed in Stefan cel Mare University – 
Suceava. For different conditions we found 
the next results for Vickers micro-
hardness: 
 

Table 3 
Results of micro-hardness measurements for 

some samples of nickel electrodeposited on 
copper substrate 

 
Sample Deposi

tion 
potenti

al 
(mV) 

Tempe
rature 
(C) 

Force 
(N) 

HV 

26 700 60 0.050 62.1 
27 750 60 0.050 71.2 
28 800 60 0.050 76.6 

29 850 60 0.050 78.6 
30 900 60 0.050 68.7 

0
20
40
60
80

100

700 750 800 850 900

mV

H
V

 
Figure 6. Micro-hardness vs. deposition 

potential 
 

It was observed that micro-harness 
increases directly with deposition 
potential, but when it is surpassing a limit, 
will follow a decrease of the micro-
hardness. This is again a result confirmed 
by other studies. 

 

  
Figure 7. Photo of 

hardness indent for 
nickel deposited on 

copper substrate from 
a Watts bath with 

addition of PVP, at -
1000 mV potential and 

65C temperature 
(Shimadzu HMV) 

Figure 8. Photo of 
hardness indent for 
nickel deposited on 

copper substrate from a 
Watts bath with 

addition of PVP, at -900 
mV potential and 65C 
temperature (Shimadzu 

HMV) 
 
 
 
4. Conclusion 

 
The deposited Ni and Zn-Ni alloys are 
important in technique. To obtain the 
stoichiometric composition it has to follow 
carefully the values of the physical and 
chemical parameters. 
The quality of the deposed could be 
controlled through the electrolyte 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava  
Volume X,  Issue 4 - 2011 

 
 

94 
 

concentration, discharge potential and the 
working temperature. The analyses SEM-
EDX and XRD confirm that the zinc-
nickel alloys were formed. Also it is 
confirmed that the percents of those two 
metals in the deposed alloy depend of 
working conditions. Conditions to obtain 
desired properties like hardness and 
brightness were established. 
 
5. Acknowledgment 

 
This paper was supported by the project 
"Progress and development through post-
doctoral research and innovation in 
engineering and applied sciences– PRiDE - 
Contract no. POSDRU/89/1.5/S/57083", 
project co-funded from European Social 
Fund through Sectorial Operational 
Program Human Resources 2007-2013. 
 
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	5. Acknowledgment