Materials Sciences and Applications, 2011, 220-225
doi:10.4236/msa.2011.24028 Published Online April 2011 (
Copyright © 2011 SciRes. MSA
Corrosion Inhibition of Copper in 3% NaCl
Solution by Derivative of Aminotriazole
Karima Rhattas1, Mohammed Benmessaoud1,2, Mostafa Doubi1, Najjat Hajjaji1, Abdellah Srhiri1
1Laboratory of Electrochemistry, Materials and Environment (LEME), Faculty of Sciences, Ibn Tofail University, Morocco; 2University
of Mohammed V Agdal, Energy Systems Laboratory, Materials and Environment, High School of Technology, Salé Medina, Morocco
Received November 6th, 2010; revised January 26th, 2011; accepted February 21st, 2011.
The inhibiting effect of N-decyl-3-amino-1,2,4-triazole (TN10) against Copper corrosion in aerated 3% NaCl, has been
developed. Potentiodynamic measurements and electrochemical impedance spectroscopy have been applied to deter-
mine the corrosion rate. Scanning electron microscopy (SEM) studied surface morphology has been also used to char-
acterize electrode surface. The obtained results indicate that TN10 acts as a good mixed-type inhibitor retarding both
anodic and cathodic reactions. An increase of TN10 concentration leads to a decrease of corrosion rate and inhibition
efficiency increase.
Keywords: Copper, Triazole, 3% NaCl Solution, Corrosion, Inhibition
1. Introduction
Due to its high electrical and thermal conductivity and
good mechanical workability, copper is a material widely
used in pipelines for domestic and industrial water utili-
ties, including sea water, heat conductors, and heat ex-
changers [1]. In spite of the relatively noble potential of
copper, its corrosion takes place at a significant rate in
sea water and chloride environments [2-9]. It is generally
accepted that the anodic dissolution of copper in chloride
environments is influenced by the chloride ions concen-
tration. At chloride concentrations lower than 1 M, the
dissolution of copper occurs through the formation of
CuCl, which is not protective enough and is converted to
the soluble CuCl2 by reacting with excess chloride [10].
Heterocyclic compounds, especially nitrogen-based
ones, are effective inhibitors, being coordinate with
Cu(0), Cu(I) or Cu(II) via their nitrogen atoms through
lone pair electrons to form polymeric complexes with
copper [11-17]. These form an adsorbed protective film
on the copper surface, providing inhibition of corrosion
by acting as a barrier to aggressive ions such as chloride
[18-20]. Polar functional groups such as nitrogen, sulfur,
and oxygen and conjugated double bonds are considered
reaction centers in establishing the adsorption process
[21,22]. In others previous work, the influence of organic
compounds on the corrosion of copper in neutral solution
have been studied [23-28].
The present investigations discusses the results ob-
tained in studying the corrosion behavior of pure copper
in aerated 3% NaCl solution in absence and in presence
of an aminotriazole derivative like N-decyl-3-amino-1,
2,4-triazole noted (TN10). The electrochemical methods
and surface characterization have been used to charac-
terize the inhibiting effect.
2. Experimental Conditions
A classic electrochemical cell with three-electrode con-
figuration was used in this study: a platinum grid as a
counter electrode, a rotating disk of pure copper (99.9%)
as working electrode, and Ag/AgCl in 3 M KCl (SSE) as
a reference one.
The working electrode was made of cylinder rod of
pure copper (Goodfellow) of 12.5 mm in diameter. A
cylinder rod of about 1 cm height was fixed to a stain-
less-steel shaft, and then the lateral part was covered with
a cataphoretic epoxyamine base paint (PPG; WT724 +
P962). First, the paint was deposited at a constant voltage
of 180 V during 4 min, and then cured at 180˚C for 30
min. After that, the electrode was embedded into an ep-
oxy resin (Buhler; Epoxycure), and worked out to the
cylinder shape, the outer diameter was 21 mm. Only the
cross-section of the alloy rod embedded in the epoxy
resin was used to form a rotating disk electrode. The
cataphoretic coating allowed avoiding any infiltration of
electrolyte between the metal and epoxy resin interface.
Corrosion Inhibition of Copper in 3% NaCl Solution by Derivative of Aminotriazole
Copyright © 2011 SciRes. MSA
Just before each experiment, the electrode surface was
polished by emery-paper up to 1000 grit. The corrosive
solution was prepared with distilled water and reagent
grade chemicals of NaCl. We obtain 3% of NaCl solu-
The potentiodynamic measurements were performed
using a PGP201 potentiostat/galvanostat. The electrode
was immersed for 1h in the test solution in free corrosion
conditions. Then, the polarization curves were recorded
by changing stepwise (60 mV/min) the potential.
Impedance (EIS) measurements were done using an
EG&G apparatus (model 6310), with a frequency interv-
al ranging from 100 kHz to 10 mHz.
The surface morphology of the electrode was perform-
ed by using scanning electron microscope (SEM) .
3. Results and Discussion
3.1. Voltammetry Experiments
The cathodic and anodic polarization curves of the cop-
per obtained with a RDE at 1000 rpm in 3% NaCl solu-
tion with various TN10 concentrations are presented in
Figures 1 and 2, respectively. The range of TN10 con-
centrations investigated in this work between 104 M and
103 M. All of these curves were obtained after 1 h im-
mersion of the electrode in the electrolytic solution at
open-circuit corrosion potential (Ecorr). Then cathodic and
anodic polarization curves were recorded from indepen-
dent experiments. The initial potential was stated at a
slightly more positive potential from Ecorr for the ca-
thodic scans, and conversely, it was set at a slightly more
negative value from Ecorr for the anodic scans.
In absence of TN10, the cathodic current (Figure 1)
follows the Tafel law for E > 0.6 V/SCE, and then the
corrosion current density can be determined readily after
diffusion correction (icor 127 A/cm2). For potential
more negative than 0.6 V/SCE, the current plateau ob-
served is ascribed to the limiting current of the dissolved
oxygen reduction. The adding of 0.05 mM or 0.1 mM of
TN10 into the corrosive medium is accompanied by both
a shift of Ecorr toward more positive potential, and a de-
crease of icor.
It is important to point out that for potential more posi-
tive than 0.4 V/SCE, the Tafel slope is independent of
the inhibitor concentration. In contrast, the cathodic
curves in the most negative potential domain (Figure 1)
are different in presence and absence of TN10, namely,
the limiting diffusion current corresponding to the oxy-
gen reduction is always observed. This may be explained,
for instance, by the formation of surface film which hin-
ders the diffusion of dissolved oxygen towards the elec-
trode surface in addition to the hydrodynamic diffusion
The extrapolation of cathodic polarization curve to the
Figure 1. Cathodic polarization curves of copper in aerated
3% NaCl without and with various concentrations of in-
hibitor TN10 at 25˚C : = 1000 rpm; |dE/dt| = 60mVs1.
open-circuit corrosion potential Ecorr allowed evaluating
the corrosion current density. The results are summarized
in Table 1. The inhibiting efficiency E in percent was
calculated according to the following expression:
Ei (1)
where i0corr and icorr denote the corrosion currents densi-
ties in absence and in presence of inhibitor, respectively.
The inhibiting efficiency increases with the TN10 con-
centration for a given temperature and immersion time,
and it reaches 99.2% for the addition of 1 mM of TN10.
In absence of inhibitor, the anodic curve (Figure 2)
exhibits two distinct domains: the first zone is located in
the vicinity of the corrosion potential and is characterized
by a steep Tafel slope whereas the second zone located
towards more positive potentials is characterized by a
quite constant current density. This limiting current den-
sity is likely governed by the solubility of CuCl2 salt
layer as mentioned elsewhere [29].
The anodic polarization curves change dramatically by
Table 1. Corrosion inhibition parameters of cooper in aer-
ated 3% NaCl solution without and with addition of TN10 at
various concentrations at 25˚C.
C, TN10 (M)bc (mV/dec)Ecorr (mV) Icorr (A/cm2)E (%)
0 239 260 5.7 -
105 262 248 1.26 77.9
5 × 105 260 238 1 82.5
104 323 191 0.27 95.3
5 × 104 234 180 0.087 98.5
103 247 142 0.047 99.2
Corrosion Inhibition of Copper in 3% NaCl Solution by Derivative of Aminotriazole
Copyright © 2011 SciRes. MSA
Figure 2. Anodic polarization curves of copper in aerated
3% NaCl without and with various concentrations of in-
hibitor TN10 at 25˚C : = 1000 rpm; |dE/dt| = 60 mV/s.
addition of TN10. This change is accompanied by a sig-
nificant decrease of the anodic current density which is
more marked near Ecorr, and an apparition of large pas-
sive domain. This later is clearly observed for various
concentrations of TN10. For instance, at 0.1 V/SCE and
0.15 V/SCE, the inhibitory efficiency E(%) is respec-
tively about 99.7%, 99.92% and about 99.99% for 0.01
mM, 0.1 mM and 1 mM of TN10 respectively. These ef-
fects can be explained by the fact that the product tested
acts by adsorption on the surface of the material and con-
tributes to an establishment of an inhibiting film rela-
tively compact.
But at higher electrode polarization, the presence of
TN10 seems to have low effect, because the anodic curr-
ent density values are sensibly equal to those obtained
without inhibitor. This may be attributed to inhibitor film
desorption [30,31] or its destruction under anodic reac-
tions like sample and water oxidations coming under the
inhibitor film and in surface sites identified.
Figure 3 shows the curve
= EIcorr%/100, as a func-
tion of log concentration C of TN10 where
is the surface
coverage. The TN10 adsorbs on the copper surface ac-
cording to the Frumkin isotherm model, which is given
by the general equation:
1 55.5
Gads, the free energy of adsorption, is equal to
37.42 kJ/mol.
The obtained results show that the TN10 inhibit both
the cathodic and anodic processes. It acts as a mixed type
3.2. Electrochemical Impedance Spectroscopy
The impedance diagrams are represented in Nyquist plot,
Figure 3. Frumkin isotherm model of TN10 on copper sur-
obtained in solution without and with 103 M of TN10
inhibitor, are presented in Figure 4. The electrode was
immersed in solution at the free corrosion potential until
a steady-state was attained.
In the absence of TN10, one capacitive loop is clearly
observed with dispersion in low frequencies range. The
associated resistance value is about 2620 kOhm·cm2, the
corresponding capacity value is in the order of 96 F/cm2.
This loop may be attributed to a charge transfer process,
occurring on the copper surface. In the same figure we
note that the impedance display of the electrode in TN10
containing solution changes in shape and size. On the
other hand it can be noticed that the impedance modulus
increased dramatically in presence of inhibitor at 103 M
concentration. The presence of two capacitive loops
seems to indicate a diffusion contribution to the begin-
ning of the experiment. At high frequency loop, it is
found that the resistance value increased in the presence
of inhibitor, whereas the double layer capacity value
found to be decreased (Table 2). The decrease of capac-
ity value was due to the adsorption of inhibitor
Figure 4. Electrochemical impedance spectra of copper in
aerated NaCl 3% without and with 103 M of TN10 at 25˚C:
= 1000 rpm.
Corrosion Inhibition of Copper in 3% NaCl Solution by Derivative of Aminotriazole
Copyright © 2011 SciRes. MSA
Table 2. Impedance measurements and inhibition efficiency
on copper in 3% NaCl solution without and with 103 M of
Solutions Rt
3% NaCl 2,620 96 0.63 -
3% NaCl + 103 M TN10 43,750 7,3 4 94
molecules on the metal surface acting as barrier to the
oxygen diffusion process.
Figure 5 presents the impedance spectra in presence
of 103 M of TN10, when the electrode rotation speed is
limited to 500 rpm and 1000 rpm after 1 h of immersion
time. No marked effect of rotation speed on impedance
diagrams is noted. This confirms the appearance of a
linear broad field in the cathodic domain, when inhibitor
is added, and makes it possible to attribute the first loop
to a charge transfer process.
3.3. Film Formed upon Copper Surface
Figure 6(a) presents the sample surface morphology
after 24 h of immersion time in 3% NaCl in absence of
TN10 (reference solution). It can be seen that the copper
surface is covered by spongy corrosion products. In con-
trast, in presence of TN10, Figure 6(b) reveals almost no
corrosion products are formed, and the grooves due to
the initial surface abrasion remain clearly visible after 24
h immersion. Some precipitates observed are NaCl crys-
tals that appeared because of insufficient surface rinsing
to avoid a wash-out of the corrosion products, if they are
present at the surface. The comparison of these two fig-
ures reveals a marked inhibiting efficiency of TN10.
Figures 7(a) and 7(b) presents the results of EDX
analysis; the copper, chloride, and oxygen are detected
Figure 5. Impedance diagrams of copper in the corrosion
test solution in presence of TN10 after 1 h of immersion at
different rotation speed.
Figure 6. SEM observation after 24 h corrosion test at the
open circuit, in absence (a) and presence (b) of inhibitor.
after the immersion in the reference solution during 24 h.
If the electrode is dipped in the solution containing 1 mM
TN10, the peak due to the oxygen decreased dramatically.
There is much less corrosion product at the electrode
surface. In contrast carbon atoms appear in the inhibiting
test, which suggests the adsorption of inhibitor to the
electrode surface. The impedance spectra exhibit, as pre-
sented above, a time constant allocable to a dielectric
surface film. It is very likely that there is a formation of
complex layer with TN10 and the corrosion products but
its thickness is too thin for SEM observation.
4. Conclusions
Electrochemical study showed that TN10 product tested
Corrosion Inhibition of Copper in 3% NaCl Solution by Derivative of Aminotriazole
Copyright © 2011 SciRes. MSA
Figure 7. EDAX spectra obtained at the copper surface
after 24 h corrosion in the corrosion test solution (a) In ab-
sence and (b) In presence of TN10.
is a good corrosion inhibitor, against copper corrosion in
3% NaCl. The inhibitor acts at the same time on the an-
odic and cathodic electrochemical processes. Polarisation
curves showed that the inhibiting effect of this compound
results in a clear decrease of the cathodic and anodic
current density values especially in the vicinity of corro-
sion potential. A remarkable inhibiting effect of TN10
was observed when its concentration is higher than 0.05
mM. Its inhibition effect increases with the increase of
inhibitor concentration and reaches 98% at 103 M.
These results were confirmed by impedance tests where
it was observed that the effect of inhibitor addition is
distinguished by an increase of the charge transfer resis-
tance value and a strong reduction of the electrochemical
interface capacity value. Surface exam with SEM has
shown that inhibitor addition leads to obtain an electrode
area without corrosion products as shown in absence of
inhibitor. All these lead to propose formation of strong
inhibiting film which could passive the metal with very
less passivity current densities value.
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