1. Corrosion inhibition of mild steel
by P,P0
-Bis (triphenylphosphonio) methyl
benzophenone dibromide in HCl solution
Ayssar Nahle´, Maysoon Al-Khayat, Ideisan Abu-Abdoun and Ibrahim Abdel-Rahman
Department of Chemistry, College of Sciences, University of Sharjah, Sharjah, United Arab Emirates
Abstract
Purpose – The purpose of this paper is to study electrochemically and by weight loss experiments the effect of P,P0
-Bis (triphenylphosphonio) methyl
benzophenone dibromide (TPPMB) on the corrosion inhibition of mild steel in 1.0M HCl solution, which will serve researchers in the field of corrosion.
Design/methodology/approach – Weight loss measurements were carried out on mild steel specimens in 1.0M HCl and in 1.0M HCl containing
various concentrations (2 £ 102 8
M and 2 £ 102 5
M) of the laboratory synthesized TPPMB at temperatures ranging from 303 to 343 K.
Findings – TPPMB was found to be a highly efficient inhibitor for mild steel in 1.0M HCl solution, reaching about 98% at the concentration of
2 £ 102 5
M at 303 K, a concentration and temperature considered to be very moderate. The percentage of inhibition in the presence of this inhibitor
was decreased with temperature which indicates that physical adsorption was the predominant inhibition mechanism because the quantity of adsorbed
inhibitor decreases with increasing temperature.
Practical implications – This inhibitor could have application in industries, where hydrochloric acid solutions at elevated temperatures are used to
remove scale and salts from steel surfaces, such as acid cleaning of tankage and pipeline, and may render dismantling unnecessary.
Originality/value – This paper is intended to be added to the family of phosphonium salt corrosion inhibitors which are highly efficient and can be
employed in the area of corrosion prevention and control.
Keywords Steel, Corrosion inhibitors, P, P0
-Bis (triphenylphosphonio) methyl benzophenone dibromide, Temkin adsorption isotherm
Paper type Research paper
Introduction
Metallic corrosion is a serious problem in many industries,
installations and civil services such as water and sewage
supplies. In searching for an economic method to prevent or
minimize corrosion, inhibitors frequently are suggested and
employed, especially in applications such as cooling systems.
Corrosion increases running costs and reduces plant efficiency,
availability and product quality.
Organic compounds containing polar groups by which a
molecule can become strongly or specifically adsorbed on
the metal surface constitute most organic inhibitors
(Damaskin et al., 1968; Okamato et al., 1962). These
inhibitors, which include the organic N, P, S, and OH groups,
are known to be similar to catalytic poisons, as they decrease the
reaction rate at the metal/solution interface without, in general,
being involved in the reaction considered. It is generally
accepted that most organic inhibitors act via adsorption at the
metal/solution interface. The mechanism by which an inhibitor
decreases the corrosion current is achieved by interfering with
some of the steps for the electrochemical process.
The corrosion inhibition of carbon steel in aggressive acidic
solutions has been widely investigated. In many industries,
hydrochloric acid solutions are used to remove scale and salts
from steel surfaces, cleaningtanks and pipelines.Thistreatment
may be prerequisite for coating by electroplating, galvanizing or
painting techniques. The acid must be treated to prevent an
extensive dissolution of the underlying metal. The treatment
involves addition of some organic inhibitors to the acid solution
that are adsorbed at the metal/solution interface by displacing
water molecules on the surface and forming a compact barrier
film.
While extensive literature exists on corrosion inhibition in
acid media, detailed knowledge of the mode of action of
inhibitors is still lacking.
Many authors have used various nitrogen-containing
compounds in their corrosion inhibition investigations. These
compounds have included quaternary ammonium salts
(Beloglazov et al., 1991; Fokin et al., 1983; Nahle´, 1997,
1998, 2002; Nahle´ and Walsh, 1995; Savithri and Mayanna,
1996; Vasudevant et al., 1995), polyamino-benzoquinone
polymers (Muralidharan et al., 1995), benzimidazole and
imidazole derivatives (Benali et al., 2007; El Ashry et al., 2008;
Khaled, 2003; Popova, 2007; Popova et al., 2004, 2007;
Sastri et al., 2008; Scendo and Hepel, 2008; Vishwanatham and
Kumar, 2005; Zhang et al., 2004, 2008), bipyrazole
(Tebbji et al., 2011), stilbazole (Nahle´ et al., 2007),
substituted aniline-N-salicylidenes (Talati et al., 2005),
amides (Tu¨ken et al., 2002), heterocyclic compounds
(Fattah et al., 1991; Granese et al., 1992), and cationic
surfactants (Al Lohedan et al., 1996; Qiu et al., 2005).
Other authors worked on phosphorous-containing and sulfur-
containing inhibitors (Ateya et al., 1984a, b; Fouda et al., 1986;
The current issue and full text archive of this journal is available at
www.emeraldinsight.com/0003-5599.htm
Anti-Corrosion Methods and Materials
60/1 (2013) 20–27
q Emerald Group Publishing Limited [ISSN 0003-5599]
[DOI 10.1108/00035591311287410]
The authors would like to thank the College of Graduate Studies and
Research at the University of Sharjah for financially supporting this
research project, as well as our research group entitled “Corrosion
Prevention & Control”.
20

2. Nahle´, 2001; Nahle´ et al., 2005, 2007, 2008; Raicheva et al.,
1993; Sanad et al., 1995). Other studies involved the effect of
addition of some ions on the inhibition efficiency of some
organic compounds. These ions included chromium
(Zucchi et al., 1992), iodide (Huang et al., 1993; Popova et al.,
2003a, b), and chloride (Yamaguchi and Nishihara, 1994). The
structural effect of organic compounds as corrosion inhibitors
also has beenstudied (Fouda et al., 2005;Kobayashi et al., 1993;
Popova et al., 2003a, b, 2007; Skryler et al., 1991). In all these
studies, the nitrogen atom(s) in the compounds were shown to
be able to absorb very well on the metal surface and form
protective layer, which in turn increased the corrosion
inhibition with the increase in the concentration of the
inhibitor, in some cases reaching 99 percent inhibition
(Nahle´, 1997).
No studies have been reported on P,P0
-Bis
(triphenylphosphonio) methyl benzophenone dibromide, in
terms of studying both the electrochemical and the temperature
effects on the corrosion inhibition of carbon steel in 1.0M HCl
solution. Plain carbon steel was chosen for the study because
high temperature aggressive acids are used widely in industries
in connection with the use of mild and low alloy steels.
Experimental details
Synthesis of P,P0
-Bis (triphenylphosphonio) methyl
benzophenone dibromide
P,P0
-Bis (triphenylphosphonio) methyl benzophenone
dibromide (TPPMB) (Scheme 1) was prepared according to
the procedure described by Neckers and Abu-Abdoun
(1984).
Instrumentation
The experimental set-up consisted of a 250-mL round bottom
glass flask fitted with a reflux condenser and a long glass rod
on which the specimen was hooked and in turn immersed in a
thermally controlled water bath.
Sample preparation
Rectangular specimens (1 cm £ 2.3 cm £ 0.3 cm) were cut
from large sheet of 3 mm thick plain carbon steel (IS 226
containing 0.18% C, 0.6% Mn, and 0.35% Si) supplied by
“Reliable Steel Traders”, Sharjah, UAE, and were used for
the weight loss measurements. A 2-mm diameter hole was
drilled close to the upper edge of the specimen and served to
be hooked with a glass rod for immersion purposes. Prior to
each experiment, the specimens were polished with 600 grade
emery paper, rinsed with distilled water, degreased with
acetone, dried, and finally weighed precisely on an accurate
analytical balance.
Measuring procedure
The flask was filled with 100 mL of 1M HCl solution with and
without TPPMB of various concentrations, and then placed in a
water bath. As soon as the required working temperature was
reached, the sample coupon was immersed in the solution, and
left there for exactly 6 h, after which it was removed, rinsed with
distilled deionized water, degreased with acetone, dried, and
finally weighed precisely on an accurate analytical balance. This
procedure was repeated with all the samples with a variety of
inhibitor concentrations ranging from 2 £ 102 8
M up to
2 £ 102 5
M; and at temperatures ranging from 303 to 343 K.
Results
Weight loss corrosion tests were carried out on the steel samples
in 1M HClin theabsence and presence of TPPMB overa period
of 6 h. Table I represents the corrosion rates (mg.cm2 2
.h2 1
),
and the percentage efficiencies (%) for the studied inhibitor
with concentrations varying from 2 £ 102 8
M to 2 £ 102 5
M at
303, 313, 323, 333, and 343 K, respectively. The percentage
efficiency was calculated according to the following expression:
% Inhibition ¼
WUninh: 2 WInh:
WUninh:
£ 100 ð1Þ
where:
WUninh. ¼ corrosion rate without inhibitor.
Winh. ¼ corrosion rate with inhibitor.
Figures 1 and 2 show the plots of the corrosion rate of
(TPPMB) as a function of concentration at temperatures of
303, 313, 323, 333, and 343 K. At 303 K (Figure 1) the
corrosion rate dropped from 0.961 mg.cm2 2
.h2 1
(1M HCl in
the absence of the inhibitor) to 0.427 mg.cm2 2
.h2 1
when
2 £ 102 8
M of TPPMB was present in the 1M HCl. The
corrosion rate continued to decrease slightly to reach
0.281 mg.cm2 2
.h2 1
(70.8 percent inhibition) at a
concentration of 2 £ 102 7
M, followed by a steep decrease to
reach 0.038 mg.cm22
.h2 1
when the inhibitor concentration
was 2 £ 102 6
M; and finally, at higher concentration
(2 £ 102 5
M) the corrosion rate as initially decreased slightly
to reach 0.018 mg.cm2 2
.h2 1
(98.1 percent inhibition). At
313 K (Figure 1), the curve had a similar shape to that obtained
at 303 K. At concentrations greater than 2 £ 102 7
M, the
corrosion rate decreased steeply and reached about
0.058 mg.cm2 2
.h2 1
(95.8 percent) at 2 £ 1025
M.
At 323 K (Figure 1), the concentration of the inhibitor
between 2 £ 102 8
and 2 £ 102 7
M had very slight effect on the
corrosion rate, whereas at higher concentrations, the corrosion
rate dropped from 2.579 mg.cm2 2
.h2 1
(at 2 £ 102 7
M) down
to 0.382 and 0.305 mg.cm2 2
.h2 1
at 2 £ 102 6
M and
2 £ 102 5
M, respectively.
In Figure 2, the corrosion rates at 333 and 343 K are shown
as a function of the concentration of TPPMB. It can be
observed that the presence of the TPPMB inhibitor at these
high temperatures acted as a corrosion inhibitor, reaching a
percent inhibition of 91.1 and 86.0 percent when 2 £ 102 5
M
inhibitor was employed at 333 K and 343 K, respectively.
Figure 3 shows the plots of the percent inhibition versus the
concentration of the inhibitor at temperatures of 303, 313,
323, 333, and 343 K, respectively. This figure shows that the
percent inhibition was significantly affected by the increase of
temperature (303-343 K) over all concentrations of inhibitor
(2 £ 102 8
-2 £ 102 5
M) and the presence of increased
concentrations of the inhibitor greatly increased the percent
inhibition at all temperatures.
The data obtained from the weight loss measurements were
plotted in accordance to the Arrhenius equation:
Scheme 1 Structure of P,P0
-Bis (triphenylphosphonio) methyl
benzophenone dibromide
2Br–
CH2P+ Ph3Ph3 P+ CH2
O
C
Corrosion inhibition of mild steel by TPPMB in HCl solution
Ayssar Nahle´ et al.
Anti-Corrosion Methods and Materials
Volume 60 · Number 1 · 2013 · 20–27
21

3. ln rate ¼ 2
Ea
RT
þ const: ð2Þ
where:
Ea ¼ activation energy (kcal.mol2 1
).
R ¼ gas constant (kcal.mol2 1
).
T ¼ absolute temperature (K).
const. ¼ constant.
Figure 4 shows the Arrhenius plot of the corrosion of
carbon steel in 1M HCl solution (Ln corrosion rate as a
function of 1/T) with and without the presence of TPPMB
at concentrations ranging from 2 £ 102 8
M to
2 £ 102 8
M. From this Figure, the slope (2Ea/R) of
each individual line was determined and used to calculate the
activation energy according to equation (2), and taking
R ¼ 1.987 £ 102 3
kcal.mol2 1
(Table II). The increase of
concentration of TPPMB (from 2 £ 102 8
M to 2 £ 102 8
M),
increased the activation energies for the corrosion of the
steel in 1M HCl (initially 18.27 kcal.mol2 1
) (Table II).
The increase in the activation energies for corrosion is
attributed to a decrease in the adsorption of the inhibitor
on the metal surface as the temperature increased.
Subsequently, an increase in the corrosion rate will result due
to the greater exposed area of the metal surface to the acid.
Table III shows the surface coverage of various
concentrations of TPPMB (from 2 £ 102 8
M to 2 £ 102 5
M)
on steel surface as a function of temperature. These values were
extracted from the corresponding percent efficiency values
reported earlier in Table I. The plot of surface coverage, u,
against the natural logarithm of the concentration, ln C, for steel
Figure 1 Effect of concentration of P,P0
-Bis (triphenylphosphonio)
methyl benzophenone dibromide on the corrosion rate (mg.cm2 2
.h2 1
)
of steel in 1M HCl at various temperatures
0
0.5
1
1.5
2
2.5
3
3.5
1.0E-08 1.0E-07 1.0E-06 1.0E-05 1.0E-04
Concentration, M
CorrosionRate,mg.cm–2
.h–1
Concentration
(M)
Corrosion Rate(mg.cm–2.h–1) at Various Temperatures
303 313 323 333 343
2E–08 0.427 0.749 3.064
0.0000002 0.218 0.612 2.579
0.000002 0.038 0.088 0.382
0.00002 0.018 0.058 0.305
Notes: ♦ 303 K; 313 K; 323 K
Figure 2 Effect of concentration of P,P0
-Bis (triphenylphosphonio)
methyl benzophenone dibromide on the corrosion rate (mg.cm2 2
.h2 1
)
of steel in 1M HCl at various temperatures
0
5
10
15
20
25
1.0E-08 1.0E-07 1.0E-06 1.0E-05 1.0E-04
Concentration, M
CorrosionRate,mg.cm–2
.h–1
Concentration
(M)
Corrosion Rate(mg.cm–2.h–1) at Various Temperatures
303 313 323 333 343
2E–08 9.448 23.584
0.0000002 7.501 20.367
0.000002 1.259 4.306
0.00002 1.09 3.677
Notes: + 333 K; 343 K
Table I Effect of concentration of P,P0
-Bis (triphenylphosphonio) methyl benzophenone dibromide on the corrosion rate (mg.cm2 2
.h2 1
) and
percentage efficiency of mild steel in 1M HCl at various temperatures
Temperature/K
303 313 323 333 343
Concentration of inhibitor Corr. rate % efficieny Corr. rate % efficieny Corr. rate % efficieny Corr. rate % efficieny Corr. rate % efficieny
1M HCl 0.961 – 1.394 – 4.671 – 12.225 – 26.280 –
1M HCl 12 3 1028
M 0.427 55.6 0.749 46.3 3.064 34.4 9.448 22.7 23.584 10.3
1M HCl 1 2 3 1027
M 0.281 70.8 0.612 56.1 2.579 44.8 7.501 38.6 20.367 22.5
1M HCl 12 3 1026
M 0.038 96.0 0.088 93.7 0.382 91.8 1.259 89.7 4.306 83.6
1M HCl 12 3 1025
M 0.018 98.1 0.058 95.8 0.305 93.5 1.093 91.1 3.677 86.0
Corrosion inhibition of mild steel by TPPMB in HCl solution
Ayssar Nahle´ et al.
Anti-Corrosion Methods and Materials
Volume 60 · Number 1 · 2013 · 20–27
22

4. in the presence of the various inhibitor concentrations is shown
in Figure 4. After examining the data and adjusting them to
different theoretical adsorption isotherms, it was concluded
that all inhibitors were adsorbed on the steel surface according
to the Temkin Isotherm (Table IV):
22au ¼ lnK C ð3Þ
where:
a ¼ molecular interaction constant.
u ¼ degree of coverage.
K ¼ equilibrium constant for the adsorption reaction.
C ¼ concentration of the inhibitor.
The equilibrium constant for the adsorption reaction, K, is
related to the standard free energy of adsorption via the
following equation given by Damaskin et al.:
K ¼
1
55:5
exp 2
DG
RT
ð4Þ
where:
K ¼ equilibrium constant for the adsorption reaction.
55.5 ¼ concentration of water (mol.L21
).
DG ¼ standard free energy (kcal.mol2 1
).
R ¼ gas constant (kcal.mol2 1
).
T ¼ absolute temperature (K).
According to equation (3), the straight lines shown in Figure 4
will have the following slopes and intercepts:
Slope ¼ 2
1
2a
ð5Þ
Intercept ¼ 2
1
2a
ln K ð6Þ
Figure 3 Effect of concentration of P,P0
-Bis (triphenylphosphonio)
methyl benzophenone dibromide on the percent inhibition of steel in
1M HCl at various temperatures
0
10
20
30
40
50
60
70
80
90
100
1.0E-08 1.0E-07 1.0E-06 1.0E-05 1.0E-04
Inhibitor Concentration, M
%Inhibition
Concentration
(M)
Inhibition% at Various Temperatures
303 K 313 K 323 K 333 K 343 K
2E–08 55.6 46.3 34.4 22.7 10.3
0.0000002 70.8 56.1 44.8 38.6 22.5
0.000002 96 93.7 91.8 89.7 83.6
0.00002 98.1 95.8 93.5 91.1 86
Notes: ♦ 303 K; 313 K; 323 K + 333 K; 343 K
Figure 4 Effect of temperature on the corrosion rate of steel in 1M HCl
solution with and without the presence of various concentrations of
P,P0
-Bis (triphenylphosphonio) methyl benzophenone dibromide
–5
–4
–3
–2
–1
0
1
2
3
4
2.9 3 3.1 3.2 3.3 3.4
1/T x 103
, K–1
LnCorrosionRate,mg.cm–2
.h–1
(1/T)x103
K–1
1M HCl
1M HCl
+ 2x10–8
M
1M HCl
+ 2x10–7
M
1M HCl
+ 2x10–6
M
1M HCl
+ 2x10–5
M
3.3 –0.03978 –0.85097 –1.2694 –3.27017 –4.01738
3.19 0.332177 –0.28902 –0.49102 –2.43042 –2.8473
3.1 1.541373 1.11972 0.9474 –0.96233 –1.18744
3 2.503483 2.2458 2.01504 0.23032 0.08893
2.92 3.268808 3.16057 3.01392 1.46001 1.3021
Notes: ♦ 1 M HCI K; 1 × 10–7M; 1 × 10–6M; + 1 × 10–5M;
1 × 10–4M; • 1 × 10–3M
Table II The activation energy (Ea) for the corrosion of mild steel in 1M
HCl with and without P,P0
-Bis (triphenylphosphonio) methyl
benzophenone dibromide inhibitor at various concentrations
Activation energy, Ea (kcal.mol21
)
System 2 3 102 5
M 2 3 1026
M 2 3 1027
M 2 3 1028
M
1M HCl 18.27 18.27 18.27 18.27
1M HCl 1
inhibitor 28.32 25.23 23.07 21.97
Corrosion inhibition of mild steel by TPPMB in HCl solution
Ayssar Nahle´ et al.
Anti-Corrosion Methods and Materials
Volume 60 · Number 1 · 2013 · 20–27
23

5. Combining equations (5) and (6) leads to the following
relationship:
Intercept ¼ Slope:ðln KÞ ð7Þ
from which the equilibrium constant for the adsorption
reaction, K, can be calculated:
K ¼ eðIntercept=SlopeÞ
ð8Þ
The standard free energy of adsorption of the inhibitor, DG0
,
can be calculated from the results in Figure 5 used to
calculate the equilibrium constant, K, and equation (4) at
various temperatures (303-343 K).
The enthalpy of adsorption, DH0
, for the inhibitor can be
calculated from the following equation:
DH0
¼ Ea 2 RT ð9Þ
The entropy, DS0
, can be calculated at various temperatures
for the inhibitor using the following equation:
DG0
¼ DH0
2 TDS0
ð10Þ
Discussion
The results summarized in Table II, show that the activation
energy (Ea) for the corrosion of steel in the presence of the
inhibitor were higher compared to the activation energy in the
absence of inhibitor at all concentrations ranging from
2 £ 102 5
M to 2 £ 102 8
M (from about 28 vs to
22 kcal.mol2 1
). This can be attributed to the fact that higher
values of Ea in the presence of inhibitor compared to its absence
are generally consistent with a physisorption, while unchanged
or lower values of Ea in inhibited solution suggest charge
sharing or transfer from the organic inhibitor to the metal
surface to form coordinate covalent bonds (Popova et al.,
2003a, b).
Tables V-VII show the thermodynamic data obtained in the
presence of the inhibitor at 2 £ 1025
M. These thermodynamic
quantities represent the algebraic sum of the values for
adsorption and desorption. The negative value of DG0
indicates the spontaneous adsorption of inhibitor on the
surface of the mild steel. The standard free energy, DG0
,
varies from 218.29 kcal.mol21
.K21
at 303 K to 215.21
kcal.mol21
.K21
at 343K. The adsorption process is believed
Figure 5 Effect of concentration of P,P0
-Bis (triphenylphosphonio)
methyl benzophenone dibromide on the surface coverage of steel in 1M
HCl at various temperatures
0
0.2
0.4
0.6
0.8
1
–18 –16 –14 –12 –10 –8
Ln Concentration, M
SurfaceCoverage
303 313 323 333 343
–10.82 0.981 0.956 0.935 0.911 0.86
–13.12 0.96 0.937 0.918 0.897 0.836
–15.42 0.708 0.561 0.448 0.386 0.225
–17.71 0.556 0.463 0.344 0.227 0.103
Notes: ♦ 303 K; 313 K; 323 K + 333 K; 343 K
Table III Effect of concentration of P,P0
-Bis (triphenylphosphonio) methyl benzophenone dibromide on surface coverage for mild steel in 1M HCl at
various temperatures
Temperature/K
303 313 323 333 343
Concentration of inhibitor Surface coverage u Surface coverage u Surface coverage u Surface coverage u Surface coverage u
1M HCl 12 3 1028
M 0.556 0.463 0.344 0.227 0.103
1M HCl 12 3 1027
M 0.708 0.561 0.448 0.386 0.225
1M HCl 12 3 1026
M 0.960 0.937 0.918 0.897 0.836
1M HCl 12 3 1025
M 0.981 0.958 0.935 0.911 0.860
Table IV The data obtained from the weight loss measurements for Arrhenius equation: (1/T) against Ln corrosion rate
Ln corrosion rate (mg.cm2 2
.h21
)
(1/T) 3 103
K21
1M HCl 1M HCl 12 3 1028
M 1M HCl 12 3 1027
M 1M HCl 12 3 1026
M 1M HCl 12 3 1025
M
3.30 20.03978 20.85097 21.26940 23.27017 24.01738
3.19 0.332177 20.28902 20.49102 22.43042 22.84731
3.10 1.541373 1.11972 0.94740 20.96233 21.18744
3.00 2.503483 2.24580 2.01504 0.23032 0.08893
2.92 3.268808 3.16057 3.01392 1.46001 1.30210
Corrosion inhibition of mild steel by TPPMB in HCl solution
Ayssar Nahle´ et al.
Anti-Corrosion Methods and Materials
Volume 60 · Number 1 · 2013 · 20–27
24

6. to be exothermic and associated with a decrease in entropy (DS)
of solute, while the opposite is true for the solvent. The
gain in entropy that accompanies the substitutional
adsorption process is attributable to the increase in the solvent
entropy. This agreeswiththe general suggestion thatthe values of
DG0
increase with the increase of inhibition efficiency
(Fouda et al., 1986, 2005) as adsorption of organic compound
is accompanied by desorption of water molecules from the
surface.
The high inhibition efficiency may be attributed to the
preferred flat orientation of this compound on the
metal surface. An interaction occurs between the delocalized
p-electrons of the two rings, the diphenyl ketone and the lone
pair of electrons on P and O atoms with the positively charged
metal surface.
Conclusion
P,P0
-Bis (triphenylphosphonio) methyl benzophenone
dibromide (TPPMB) was found to be a highly efficient
inhibitor for plain carbon steel in 1.0M HCl solution,
reaching about 98 percent at 2.0 £ 102 5
M and 303 K,
a concentration considered to be very low.
P,P0
-Bis (triphenylphosphonio) methyl benzophenone
dibromide (TPPMB) may function as a potential corrosion
inhibitor because it contains phosphorus and oxygen. It was
apparent from the molecular structure that this compound
would be adsorbed onto the metal surface through the lone
pair of electron of phosphorus and oxygen and p-electrons of
the diphenyl ketone.
The percentage of inhibition in the presence of this
inhibitor was decreased with temperature, which indicated
that physical adsorption was the predominant inhibition
mechanism because the quantity of adsorbed inhibitor
decreased with increasing temperature.
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dibromide at various temperatures (303-343 K)
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.mol2 1
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0.152 0.143 0.135 0.130 0.125
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M P,P0
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benzophenone dibromide at various temperatures (303-343 K)
DH, kcal.mol21
303 K 313 K 323 K 333 K 343 K
27.72 27.70 27.68 27.66 27.64
Corrosion inhibition of mild steel by TPPMB in HCl solution
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Corrosion inhibition of mild steel by TPPMB in HCl solution
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Further reading
Frank, W.C., Kim, Y.C. and Heck, R.F. (1978),
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heterocyclic dibromides”, J. Org. Chem., Vol. 43 No. 15,
pp. 2947-9.
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intermolecular hydrogen bonding for the induction of
liquid crystallinity in the side-chain of polysiloxanes”,
J. Amer. Soc., Vol. 114, p. 6630.
Nahle´, A. (2005), “Inhibition of corrosion of iron
in HCl solution by semicarbazides and
thiosemicarbazides”, Bulletin of Electrochemistry, Vol. 21
No. 6, pp. 275-81.
Corresponding author
Ayssar Nahle´ can be contacted at: anahle@sharjah.ac.ae
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Corrosion inhibition of mild steel by TPPMB in HCl solution
Ayssar Nahle´ et al.
Anti-Corrosion Methods and Materials
Volume 60 · Number 1 · 2013 · 20–27
27