Synthesizing new hydrazone derivatives and studying their effects on the inhibition of copper corrosion in sodium chloride solutions

Article abstract of DOI:10.1080/15533174.2010.492546

O-methoxybenzaldehydebenzoylhydrazone (O-MBH) and bis-(o- methoxybenzaldehyde)-thiocarbodihydrazone (O-MTH) were synthesized. The O-MBH and O-MTH effects on the inhibition of copper corrosion in 3.5% NaCl solution were investigated. Electrochemical measurements showed that the addition of O-MBH and O-MTH decreased the corrosion parameters of copper in the test solutions. The weight loss experiments indicated that O-MBH and O-MTH decreased the corrosion rate of copper. The data pointed out that O-MBH and O-MTH inhibit the copper corrosion in NaCl solution with inhibition efficiency in the order of O-MTH > O-MBH. Copyright Taylor & Francis Group, LLC.

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Synthesizing New Hydrazone Derivatives and
Studying their Effects on the Inhibition of Copper
Corrosion in Sodium Chloride Solutions
El-Sayed M. Sherif a b & Ayman H. Ahmed c d
a Electrochemistry and Corrosion Laboratory, Department of Physical Chemistry ,
National Research Center (NRC) , Dokki, Cairo, Egypt
b Center of Excellence for Research in Engineering Materials (CEREM), College of
Engineering , King Saud University , Al-Riyadh, Saudi Arabia
c Department of Chemistry, Faculty of Science , Al-Azhar University , Nasr City, Cairo,
Egypt
d Department of Chemistry, Faculty of Science , Al-Gabal El-Gharby University , Kamon,
Gherian, Libya
Published online: 13 Jul 2010.
To cite this article: El-Sayed M. Sherif & Ayman H. Ahmed (2010) Synthesizing New Hydrazone Derivatives and Studying
their Effects on the Inhibition of Copper Corrosion in Sodium Chloride Solutions, Synthesis and Reactivity in Inorganic,
Metal-Organic, and Nano-Metal Chemistry, 40:6, 365-372
To link to this article: http://dx.doi.org/10.1080/15533174.2010.492546
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:365–372, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.492546
Synthesizing New Hydrazone Derivatives and Studying their
Effects on the Inhibition of Copper Corrosion in Sodium
Chloride Solutions
El-Sayed M. Sherif1,2 and Ayman H. Ahmed3,4
1Electrochemistry and Corrosion Laboratory, Department of Physical Chemistry, National Research
Center (NRC), Dokki, Cairo, Egypt
2Center of Excellence for Research in Engineering Materials (CEREM), College of Engineering, King
Saud University, Al-Riyadh, Saudi Arabia
3Department of Chemistry, Faculty of Science, Al-Azhar University, Nasr City, Cairo, Egypt
4Department of Chemistry, Faculty of Science, Al-Gabal El-Gharby University, Kamon, Gherian, Libya
tance against several harsh environments, its corrosion takes
place in a significant rate in chloride containing solutions.[2−10]
One of the most important methods in the protection of copper
against corrosion is the use of organic inhibitors. Azole com-
pounds have been found to be good corrosion inhibitors for
copper.[11−13] These compounds form complexes with copper,
which are generally believed to be polymeric in nature and pro-
duce an adherent protective film on the copper surface. This
film acts as a barrier to aggressive ions such as chloride, and
therefore inhibits copper corrosion. Amines are also known to
be very effective inhibitors for metals and alloys in different cor-
rosion media.[2,3,11−14] In general, organic compounds contain-
ing polar groups including nitrogen, sulfur, and oxygen,[15−20]
and heterocyclic compounds with polar functional groups and
conjugated double bonds have been reported to be good corro-
sion inhibitors for copper,[11−13,21] aluminum,[22,23] and iron[24]
corrosion.
O-methoxybenzaldehydebenzoylhydrazone (O-MBH) and bis-
(o-methoxybenzaldehyde)-thiocarbodihydrazone (O-MTH) were
synthesized. The O-MBH and O-MTH effects on the inhibition of
copper corrosion in 3.5% NaCl solution were investigated. Electro-
chemical measurements showed that the addition of O-MBH and
O-MTH decreased the corrosion parameters of copper in the test
solutions. The weight loss experiments indicated that O-MBH and
O-MTH decreased the corrosion rate of copper. The data pointed
out that O-MBH and O-MTH inhibit the copper corrosion in NaCl
solution with inhibition efficiency in the order of O-MTH > O-
MBH.
Keywords copper corrosion, corrosion inhibition, electrochemical
experiments, hydrazone derivatives, spectroscopic analy-
ses, synthesis
INTRODUCTION
The present work was carried out to report synthesize
and characterize of o-methoxybenzaldehydebenzoylhydrazone
(O-MBH) and bis-(o-methoxybenzaldehyde)-thiocarbodihy-
drazone (O-MTH) using different spectroscopic methods. The
study was also extended to investigate the effects of two con-
centrations of O-MBH and O-MTH, 250 and 500 ppm, on the
inhibition of copper corrosion in aerated 3.5% NaCl solutions
under stagnant conditions.
Hydrazones played a central role in the development of co-
ordination chemistry. The unique characteristic of these com-
pound results is due to the fact that hydrazones obtained by the
condensation of o-hydroxy or methoxy aldehydes and ketones
with hydrazides. This in turn makes these compounds have po-
tential polynucleating ligands posing amide, azomethine and
phenol or methoxy functions.[1] Hydrazones thus offer a variety
of bonding possibilities in metal complexes.
Copper has been widely used in many applications due to
its high electrical and thermal conductivities as well as its ex-
cellent workability. Although, copper has high corrosion resis-
EXPERIMENTAL
Chemicals and Electrochemical Cell
O-methoxybenzaldehyde (Merck), sodium chloride (NaCl,
Merck, 99%) and absolute ethanol (C2H5OH, Merck, 99.9%)
were used as received. Benzoylhydrazide was prepared ac-
cording to the literature methods.[25,26] A three-electrode elec-
trochemical cell was used; a copper rod (Cu, Goodfellow,
Received 23 June 2009; accepted 5 May 2010.
Address correspondence to El-Sayed M. Sherif, Center of Excel-
lence for Research in Engineering Materials (CEREM), College of
Engineering, King Saud University, P.O. Box 800, Al-Riyadh 11421,
Saudi Arabia. E-mail: esherif@ksu.edu.sa
365

366
E. M. SHERIF AND A. H. AHMED
99.999%, 5.0 mm in diameter), a platinum foil, and a saturated were carried out by stepping the potential at 250 mV vs. SCE
Calomel electrode (SCE) were used as a working, counter, and for 120 min.
reference electrodes, respectively. The copper electrode was first
The gravimetric data were collected for rectangular cop-
polished successively with metallographic emery paper of in- per coupons (Goodfellow, 99.999%) having the dimensions of
creasing fineness of up to 800 grits. The electrode was then 3.0 cm length, 1.0 cm width and 0.20 cm thickness with an ex-
washed with doubly distilled water, degreased with acetone, posed total area of 7.6 cm2. The coupons were polished and
washed using doubly distilled water again and finally dried with dried as copper rods were weighed (m1), and then suspended
tissue paper.
in 50 cm3 solution of 3.5% NaCl with and without the desired
concentrations of O-MBH and O-MTH for different exposure
periods (6–24 days). At the end of a run, the samples were
rinsed with distilled water, dried and weighed again (m2). All
weight-loss measurements were performed in triplicates and
the maximum standard deviation in the observed weight loss
Preparation of O-MBH and O-MTH
Carbon disulphide (76.0 g, 1 mole) was added drop wisely
to a vigorously stirred solution of 250.0 g of 100% hydrazine
hydrate (5 moles) in 150 ml of water. The reaction mixture was
then heated under reflux for 30 min, cooled in an ice bath for
30 min and the precipitated thiocarbohydrazide was filtered off,
washed with ethanol and diethyl ether, and air dried. The re-
sulting product was recrystallized from a minimum amount of
water acidified with few drops of concentrated HCl. Thiocarbo-
hydrazide with 65% yield was obtained with a melting point of
171◦C.
Benzoylhydrazide (3.0 g, 0.022 mole) was dissolved in abso-
lute ethanol; the solution was then added to an ethanolic solution
of o-methoxybenzaldehyde (2.99 g, 0.022 mole). The reaction
mixture was refluxed for 2 h in the presence of 2 ∼ 3 drops
glacial acetic acid. The product was separated out, filtered off
and recrystallized from ethanol.
was
1%. The loss in weight (ꢀm, mg·m−2), the corrosion
rate (KCorr, mg·m−2·h−1), and the percentage of the inhibition
efficiency (IE%) over the exposure time were calculated as
reported in our previous studies.[2−6]
RESULTS AND DISCUSSION
Analytical and Physical Measurements for O-MBH and
O-MTH
Figure 1a shows the infrared (IR) spectrum of O-MBH on
which there are three bands located at 3130, 2986 and 2900 cm−1
assigned to νNH, νCH (aromatic) and νCH vibrations, re-
spectively. The characteristic sharp bands at 1646, 1600, 1296
and 1250 cm−1 are due to νC O (amide-I), νC N (azome-
thine), δC-O (methoxy) and δNH modes, respectively.[27] The
two strong bands at 1560 and 1470 cm−1 are most probably
due to νC C (phenyl ring) vibrations. Figure 1b shows the IR
Thiocarbohydrazide (1.5 g, 0.014 mole) dissolved in mini-
mum amount of water was treated with an ethanolic solution of
o-methoxybenzaldehyde (3.81 g, 0.028 mole) and the mixture
was refluxed on a hot plate for 3 h. The separated thiocarbo-
hydrazone was filtered, washed with ethanol, dried in air, and
finally recrystallized using acetone.
Spectroscopic Measurements
The Fourier transform infrared (FT-IR) spectra of the syn-
thesized hydrazones were recorded as KBr pellets on FT-IR
instrument Bruker (Vector 22) single beam spectrometer at a
spectral resolution 2.0 cm−1. Electronic absorption spectra were
recorded in Nujol mull using a λ35 Perkin-Elmer Ultraviolet-
Visible Spectrophotometer. Proton nuclear magnetic resonance
(1H-NMR) spectra were performed by a Jeol FX-90 Q Fourier
Transform nuclear magnetic resonance spectrometer (200 MHz)
and mass spectra of the O-MBH and O-MTH were recorded on
Shimadzu-GCMS-Q5050 instrument using the direct inlet sys-
tem.
Electrochemical and Gravimetric Techniques for
Corrosion Investigations
Electrochemical experiments were carried out by using an
EG&G model 273A potentiostat-galvanostat with 352 corro-
sion software. The potentiodynamic polarization curves were
obtained by scanning the potential of copper from -700 to 800
FIG. 1. Fourier transform infrared (FT-IR) spectra of (a) o-MBH and (b)
mV at a scan rate of 1 mV/s. Chronoamperometric experiments o-MTH.

SYNTHESIZING NEW HYDRAZONE DERIVATIVES
367
at 11.9, 11.7 ppm, 8.8, 8.9 ppm and 3.9, 3.9 ppm downfield of
TMS and assigned to the NH, CH=N and OCH3 protons, re-
spectively. The multiplets at 6.5–8 ppm in the O-MBH spectrum
are due to the aromatic protons of methoxyphenyl ring, while
that observed at 6.9–7.6 ppm in the O-MTH spectrum are of
phenyl and methoxyphenyl rings.
The mass spectra of O-MBH and O-MTH, which are depicted
in Figure 3, proved the purity of the two investigated compounds
as shown from the M+values. Moreover, its result emphasized
the proposed chemical formula as well as the correct molecular
weight of the compounds.
Based on all the above results, the structural formula of O-
MBH and O-MTH can be represented as shown in Figures 4a
and 4b. Table 1 also shows the analytical data together with the
physical properties for the two synthesized hydrazones.
Potentiodynamic Polarization Measurements
The potentiodynamic polarization curves of copper electrode
in aerated 3.5% NaCl containing (1) 0, (2) 250 and (3) 500 ppm
of (a) O-MBH and (b) O-MTH, respectively, are shown in Figure
5. It is clear from Figure 5 that the anodic branch of Cu in
aerated 3.5%NaCl solution (curves 1) shows three regions have
been reported previously.[2,4,5] While, the cathodic reaction at
this condition is the oxygen reduction,[2]
FIG. 2. Electronic spectra of (a) O-MBH and (b) o-MTH.
spectrum for O-MTH; this spectrum also shows three bands no-
ticed at 3130, 2986 and 2900 cm−1 attributed to νNH, νCH
(aromatic) and νCH, respectively. The νC N (azomethine)
band was observed at 1600 cm−1. The two bands that are
medium at 1254 and strong at 754 cm−1 are assigned to νC S
and ν(C-N) +ν(C S) of thioamide group, which has contribu-
tion from ν(C N) and ν(C S, respectively.[28]
O2 + 2H2O + 4e− = 4OH−,
[1]
The presence of oxygen accelerates the corrosion of copper
through the formation of a porous oxide film, which is in good
electrical contact with the underlying metal,[2,29]
The electronic spectrum of O-MBH is shown in Figure
2a. It clear that the figure shows six bands centered at 387,
365, 356, 348, 333 and 323 nm referred to n-π∗(C O), n-
π∗(C N), π - π∗(C O), π - π∗(C N), π - π∗(methoxyphenyl
2Cu + H2O = Cu2O + 2H+ + 2e−.
[2]
Addition of 250 ppm O-MBH (Figure 5a, curve 2) decreased
ring) and π - π∗(phenyl ring), respectively. Meanwhile, the ab- the cathodic, anodic and corrosion (jCorr ) currents, and corro-
sorption spectrum of O-MTH, as represented by Figure 2b, sion rate (KCorr ), while increasing the polarization resistance
exhibited five bands at 425, 390, 381, 371 and 363 nm as- (Rp), the degree of surface coverage (θ), as well as the per-
signed to n-π∗(C S), n-π∗(C N), π - π∗(C S), π - π∗(C N), centage of the inhibition efficiency (IE %). It also shifted the
π - π∗(methoxyphenyl ring), respectively.
corrosion potential (ECorr) slightly to the less negative direction.
1
The spectral H-NMR data are presented in Table 1. The This effect increased as the concentration of O-MBH increased
1H-NMR spectra of O-MBH and O-MTH in dimethylsulfoxide to 500 ppm, and more significant increases occurred in the pres-
(DMSO) exhibited three singlet signals with 1:1:3 integrations ence of O-MTH (Figure 5b) at the same concentrations. This
TABLE 1
Physical and analytical data for o-MBH and o-MTH compounds
1H-NMR(δ in ppm)
Empirical
formula
Molecular weight
Compound
Color
M.P.◦C ∗found (calculated) −NH− −CH=N− aromatic protons −OCH3
o-MBH
o-MTH
C15H14N2O2 Bridal white crystals 200
∗254.0 (254.3)
11.9(s)
11.7(s)
8.8(s)
8.9(s)
6.5–8(m)
6.9–7.6(m)
3.9(s)
3.9(s)
C17H18N2O2S Light yellow powder 210−13 ∗342.0 (342.4)
o-MBH: Soluble in acetone, chloroform, ethanol, DMF, and DMSO; insoluble in water and ether.
o-MTH: Soluble in acetone, chloroform, DMF, and DMSO; partially soluble in ethanol; insoluble in water and ether.

368
E. M. SHERIF AND A. H. AHMED
FIG. 3. Mass spectra of (a) o-MBH and (b) o-MTH.
was confirmed by calculating the jCorr , ECorr , cathodic (βc),
Here, jun and jin are the corrosion currents of copper elec-
and anodic (βa) Tafel slopes, maximum (jpeak) and minimum trode in absence and presence of the inhibitor, respectively.
(jmin) current peaks, KCorr , Rp, IE%, and θ obtained from The values of KCorr and Rp were also calculated as reported
Figure 5 and listed in Table 2. The jCorr and ECorr values were before.[3,30]
obtained from the extrapolation of anodic and cathodic Tafel
The decreases in jCorr , jpeak, and jmin values by the presence
lines located next to the linearized current regions. As well as, of O-MBH and O-MTH molecules (Figure 5 and Table 2) are
the values of IE% were calculated as follows,[4]
mainly due to the decrease in the chloride ion attack on the cop-
per surface. Note also that this effect increased in the presence
of O-MTH more than in the case of O-MBH. This was probably
due to the presence of C S group in addition to the presence
of two (–NH) and two methoxy (OMe) groups in the structure
of the O-MTH in compared to O-MBH (Figure 4). This means
that the ability of the O-MTH molecules to be adsorbed onto
the copper surface is higher than those of O-MBH. It is seen
from Table 2 that the value of KCorr for copper in NaCl solu-
tion alone decreased from 2.02 mpy to 1.0 and 0.64 mpy in the
presence of 250 and 500 ppm of O-MBH. These values further
decreased to 0.82 and 0.46 mpy in the presence 250 and 500
ppm O-MTH, respectively. On the other hand, the IE% increased
from 50 to 70 and from 59 to 78 when the concentrations of O-
MBH and O-MTH were increased from 250 to 500 ppm, respec-
tively. This indicates that both O-MBH and O-MTH inhibited
the corrosion sites on the copper surface by decreasing KCorr
and increasing IE%, which increases in the order O-MTH >
O-MBH.
un
Corr
j
jin
Corr
−
Corr
IE% =
x 100 %
[3]
un
j
FIG. 4. Chemical structure of (a) o-methoxybenzaldehydebenzoylhydrazone
(o-MBH) and (b) bis-(o-methoxybenzaldehyde)-thiocarbodihydrazone (o-
MTH).

SYNTHESIZING NEW HYDRAZONE DERIVATIVES
369
FIG. 6. Chronoamperometric curves for the copper electrode after stepping
the potential to 250 mV vs. SCE in aerated 3.5% NaCl solutions containing (1)
0, (2) 250, and (3) 500 ppm of (a) o-MBH and (b) o-MTH, respectively.
and (b) O-MTH, respectively, is shown in Figure 6. The highest
currents were observed in chloride solution in the absence of
the organic compounds, which agrees with the potentiodynamic
polarization behavior (Figure 5, curves 1) at the same potential.
The large decreases observed in curves 1 at the first moment
of copper immersion might be due to the thickening of the air
formed Cu2O film,[5,31]
FIG. 5. Potentiodynamic polarization curves for the copper electrode in aer-
ated 3.5% NaCl solutions containing (1) 0, (2) 250, and (3) 500 ppm of (a)
o-MBH and (b) o-MTH, respectively; potential scan rate 1 mV/s.
Chronoamperometric Measurements
The variation of current of copper electrode with time after
the potential was stepped to 250 mV vs. SCE in 3.5% NaCl so-
lutions containing (1) 0, (2) 250, and (3) 500 ppm of (a) O-MHB
1
2Cu + /2O2 = Cu2O.
[4]
TABLE 2
Corrosion parameters obtained from polarization curves shown in Figure 5 for copper electrode in 3.5% NaCl solution in absence
and presence of 250 and 500 ppm of o-MBH and o-MTH, respectively
Parameter
ECorr
/
jCorr
/
Ba/
βc/
jpeak
/
jmin
/
KCorr /
Solution
mV µA cm−2 mVdec−1 mVdec−1 µA cm−2 gµA cm−2 Rp/kꢁ mpy IE/%
θ
3.5% NaCl only
−280
4.40
2.20
1.40
1.80
1.00
75
85
110
95
50
52
60
55
80
2750
8000
1650
2000
20
2700
600
750
1400
12
2.96
6.38
12.1
8.42
20.9
2.02
1
0.64
0.82
0.46
–
250 ppm o-MBH added −220
500 ppm o-MBH added −240
250 ppm o-MTH added −255
500 ppm o-MTH added −260
50 0.50
70 0.70
59 0.59
78 0.78
120

370
E. M. SHERIF AND A. H. AHMED
FIG. 8. (a) Variations of the weight loss (ꢀm) and (b) pH with time for
the copper coupons in 3.5% NaCl solutions containing (1) 0, (2) 250, and (3)
500 ppm of O-MTH.
FIG. 7. (a) Variations of the weight loss (ꢀm) and (b) pH with time for
the copper coupons in 3.5% NaCl solutions containing (1) 0, (2) 250, and (3)
500 ppm of O-MBH.
or as follows,
per corrosion in chloride solution, which increases in the order
O-MTH > O-MBH.
2CuCl + H2O = Cu2O + 2H+ + 2Cl−.
[5]
Weight-loss, pH Measurements, and Inhibition Efficiency
The variations of the weight loss (ꢀm) vs. time for the copper
coupons in 3.5% NaCl solutions containing (1) 0, (2) 250, and
(3) 500 ppm of O-MBH and O-MTH are shown in Figures 7a
and 8a, respectively. The accompanying changes in pH of these
solutions are also presented in Figures 7b and 8b, respectively.
It is seen from Figures 7a and 8a that the weight-loss of copper
in chloride solution alone, (lines 1) recorded 47 mg/m2 after 6
days, increased to 174 mg/m2 in 24 days. Also, the accompanied
change in pH of the solution (Figures 7b and 8b (lines 1))
increased from 6.5 to 8.6. This suggests that a significant amount
of copper must have been dissolved in the form of CuCl−2 . Since
the cathodic couple of the corrosion reaction of copper is the
reduction of oxygen, the rate of generation of OH− ions, Eq.
(1), is the same as that of CuCl−2 ions,
This film dissolved by time due to the increase of current
values again, where this oxide film is not protective and not
compact enough to decrease the chloride ions attack. As the time
increases, the current values decreased due to the formation of
corrosion products, which accumulate on the copper to cover up
the entire surface. The EDS profile analysis of copper at similar
conditions[4] indicated that only Cu, Cl and O were existed on
the surface.
The presence of 250 ppm O-MBH in the chloride solution,
Figure 6a, significantly decreased the currents especially in the
first 60 min after which the current increased again. Up on
increasing the concentration of O-MBH to 500 ppm further de-
creases in the current values were recorded. With addition of
O-MTH, Figure 6b, the current values decreased at both con-
centrations more than that measured for O-MBH. This agrees
with the polarization data and provides another confirmation
on the ability of these synthesized hydrazones to inhibit cop-
CuCl + Cl− = CuCl−2 .
[6]

SYNTHESIZING NEW HYDRAZONE DERIVATIVES
371
at 3% NaCl,[29] which indicates on the increase of copper disso-
lution with increasing both the immersion time and pH values.
The presence of O-MBH and O-MTH at 250 ppm (lines 2)
decreased both the weight loss and the corresponding pH values.
This effect significantly increased when the concentration of the
organic compounds was increased to 500 ppm. O-MBH and O-
MTH thus bestowed the protection ability to its maximum by
further decreasing the loss in weight and pH values, as can be
seen from lines 3. This is due to the adsorption of O-MBH and
O-MTH molecules onto the copper surface, which could prevent
the formation of cuprous chloride and oxychloride complexes.
In order to shed more light on the effect of O-MBH and O-
MTH on copper corrosion, the variations of IE% obtained from
the loss in weight were plotted versus time and the data are
shown in Figure 9. The IE% of O-MBH calculated for 250 ppm
after 6 days was ∼ 34 increased to ∼ 43 in 24 days. These values
increased to 46 and 53, respectively, when the concentration of
O-MBH was increased to 500 ppm. In the presence of O-MTH,
the IE% recorded higher values, where 250 ppm gave 41 after
6 days, increased to 50 in 24 days and the values recoded with
500 ppm were 49 and 61, respectively. In addition to the data
shown in Figure 9, we also calculated other parameters such
as the degree of surface coverage and the corrosion rate from
the weight loss data, aslisted in Table 3; the calculations were
made as in our previous work.[5] In fact, these results provided
another evidence for the ability of these compounds on the inhi-
bition of copper surface, which increases in the order O-MTH >
O-MBH.
FIG. 9. Change of the inhibition efficiency (IE %) obtained by loss in weight
with time for copper coupons in aerated solutions of 3.5% NaCl containing (1)
250 and (2) 500 ppm of (a) o-MBH and (b) o-MTH, respectively.
CONCLUSIONS
O-MBH and O-MTH were synthesized using infrared spec-
tra, electronic absorption spectra, and nuclear magnetic res-
Thus, the corrosion process is accompanied by a surface alka- onance measurements. The purities, chemical formulae, and
linization as reported previously.[2] This agrees with our pre- molecular weights of the two compounds were confirmed by
vious work[2,3,6] and with the data obtained by quartz crystal mass spectroscopy investigations. O-MBH and O-MTH were
microbalance and scanning tunneling microscopy experiments also tested as corrosion inhibitors for copper in aerated 3.5%
TABLE 3
Change of the degree of surface coverage (θ) and the corrosion rate (KCorr (mg.m−2.h−1)) obtained from weigh loss data for
copper coupons in aerated 3.5% NaCl solutions in absence and presence of o-MBH and o-MTH, respectively
Solution
250 ppm o-MBH 500 ppm o-MBH 250 ppm o-MTH 500 ppm o-MTH
Time
Parameter
3.5% NaCl only
added
added
added
added
6 days
θ
–
0.33
–
0.32
–
0.31
–
0.30
0.34
0.22
0.40
0.20
0.41
0.19
0.43
0.18
0.46
0.18
0.48
0.17
0.50
0.17
0.53
0.17
0.40
0.2
0.48
0.17
0.54
0.15
0.57
0.15
0.61
0.14
KCorr (mg.m−2.h−1
)
)
)
)
12 days
18 days
24 days
θ
0.45
0.175
0.47
0.17
0.50
0.15
KCorr (mg.m−2.h−1
θ
KCorr (mg.m−2.h−1
θ
KCorr (mg.m−2.h−1

372
E. M. SHERIF AND A. H. AHMED
NaCl solutions using electrochemical and gravimetric tech- 12. Sherif, E.M., Erasmus, R.M., and Comins, J.D. Colloid Interface Sci., 2007,
309, 470.
niques along with pH measurements. Electrochemical measure-
ments revealed that both O-MBH and O-MTH decrease the
cathodic, anodic and corrosion currents, and shift the potential
slightly to the less negative values. Moreover, the presence of
13. Sherif, E.M., Erasmus, R.M., and Comins, J.D. Colloid Interface Sci., 2007,
311, 144.
14. Srivastafa, R.D., Mukerjee, R.C., and Agarwal, A.K. Corros. Sci., 1979,
19, 27.
these compounds decreased the absolute dissolution current of 15. Sherif, E.M., Erasmus, R.M., and Comins, J.D. J. Appl. Electrochem., 2009,
39, 83.
copper and this effect increased with increasing their concen-
16. Sherif, E.M., Erasmus, R.M., and Comins, J.D. Corros. Sci., 2008, 50,
trations. Weight loss–time data were in good agreement with
those obtained by electrochemical measurements. In addition,
the variation of pH values exhibited a linear relationship with the
3439.
17. Zhang, D.-Q., Gao, L.-X., and Zhou, G.-D. J. Appl. Surf. Sci., 2004, 225,
287.
copper dissolution rate in chloride solutions, while the presence 18. Christy, A.G., Lowe, A., Otieno-Alego, V., Stoll, M., and Webster, R.D. J.
Appl. Electrochem., 2004, 34, 225.
19. Zucchi, F., Trabanelli, G., and Fonsati, M. Corros. Sci., 1996, 38,
of the organic compounds decreased considerably the increase
of pH by limiting the dissolution of copper. Results together
are internally consistent with each other showing clearly that
O-MBH and O-MTH produced significant inhibition efficiency
2019.
20. Mansikkama¨ki, K., Johans, C., and Kontturi, K. J. Electrochem. Soc., 2006,
153, B22.
against copper corrosion in 3.5% NaCl solutions considering 21. Sherif, E.M., El Shamy, A.M., Ramla, M.M., and El Nazhawy, A.O.H.
Mater. Chem. Phys., 2007, 102, 231.
O-MTH is more effective corrosion inhibitor than O-MBH.
22. Sherif, E.M., and Park, S.-M. J. Electrochem. Soc., 2005, 152, B205.
23. Sherif, E.M., and Park, S.-M. Electrochim. Acta, 2006, 51, 1313.
24. Sherif, E.M., Erasmus, R.M., and Comins, J.D. Electrochim. Acta, 2010,
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