Corrosion-protective properties of 1-phenacylmethyl-2- arylcarbamido(arylthiocarbamido)pyridinium bromides

Article abstract of DOI:10.1134/S1070427206120123

Inhibiting effect of 1-phenacylmethylpyridinium bromides containing urea or thiourea substituents in the pyridinium ring on steel and zinc corrosion in sulfuric acid solutions was studied.

Full text of DOI:10.1134/S1070427206120123

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 12, pp. 1969 1972.
Pleiades Publishing, Inc., 2006.
Original Russian Text
R.I. Yurchenko, I.S. Pogrebova, T.N. Pilipenko, T.E. Shubina, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79,
No. 12, pp. 1993 1997.
APPLIED ELECTROCHEMISTRY
AND CORROSION PROTECTION OF METALS
Corrosion-Protective Properties of 1-Phenacylmethyl-2-
arylcarbamido(arylthiocarbamido)pyridinium Bromides
R. I. Yurchenko, I. S. Pogrebova, T. N. Pilipenko, and T. E. Shubina
Kievskii Politekhnicheskii Institut National Technical University of Ukraine, Kiev, Ukraine
Received May 11, 2006
Abstract Inhibiting effect of 1-phenacylmethylpyridinium bromides containing urea or thiourea substituents
in the pyridinium ring on steel and zinc corrosion in sulfuric acid solutions was studied.
DOI: 10.1134/S1070427206120123
We found in [1, 2] that 1-phenacylmethylpyridini-
um bromides (I) are inhibitors of steel acid corrosion:
phenacyl and pyridinium fragments, can be involved
in adsorption, we may expect that compounds II and
III should have a strong inhibiting effect on the steel
acid corrosion.
+
R
N
The compounds studied were prepared by the reac-
tion between 2-aminopyridine with the corresponding
arylisocyanates or arylisothiocyanates, followed by
alkylation of the compounds obtained with -bromo-
acetophenone:
--
Br
O
I
Introduction into the second position of the pyri-
dinium ring in Ia (R = H) of an amino group (com-
O
RNCX
pound Ib, R = NH ) enhances the inhibiting effect,
whereas transformation of Ib into 1-phenacylmethyl-
H N
2
N
RN
H
N
H
N
2
2-benzamidopyridinium bromide (Ic) substantially
weakens it because of a decrease in the electron den-
sity on the nitrogen atom of the amino group. A dif-
X
BrCH COPh
2
+
N
RN
N
H
ferent behavior is shown by amides [I; R = R CONH]
1
in which substituents R contain groups that can be
--
1
H
Br
independently involved in adsorption on the metal
surface. Introduction of MeO group into the p-position
of the phenyl ring of the benzamide group of com-
pound Ic, or replacement of the latter with a heteryl-
O
where X = O, R = (a) C H , (b) 4-CH C H ,
(c) 4-ClC H4 (II); X = S, R = (a) C H and
6
5
3
6
4
6
6
5
amide group (R = HetCONH ) enhances the inhibit-
(b) 4-CH OC H (III).
2
3
6
4
ing effect as compared to Ic.
The structures of compounds synthesized were
confirmed by IR and NMR spectra.
In this study, we considered, in order to further
examine of the correlation between the structure and
inhibiting effect of pyridinium salts, 1-phenacylmeth-
yl-2-arylcarbamidopyridinium bromides (II) and
EXPERIMENTAL
-
2-arylthiocarbamidopyridinium bromides (III). As
1-(2-Oxo-2-phenylethyl)-2-(3-phenylcarbamido)-
pyridinium bromide (IIa), 1-(2-oxo-2-phenylethyl)-2-
[3-(4-methylphenyl)carbamido]pyridinium bromide
(IIb), 1-(2-oxo-2-phenylethyl)-2-[3-(4-chlorophenyl)-
carbamido]-pyridinium bromide (IIc), 1-(2-oxo-2-
known [3], many urea and thiourea derivatives are ef-
ficient inhibitors of acid corrosion of iron and steels.
In addition, taking into account that arylurea and aryl-
thiourea fragments of these compounds, similarly to
1969

1970
YURCHENKO et al.
Table 1. Effective charges q in compounds of the general formula
4
3
C
5
C
C
C
C
2
+
6
1
N
R
--
Br
Ph
7
O
q
Com-
pound
R
N1
C2
C3
C4
C5
C6
O8
N8
O(S)9
N10
8
Ib
N H
0.351 0.059 0.274 0.133 0.279 0.466 0.573 0.801
2
8
9 10
IIa
IIb
IIc
N HCO N HC H
0.328 0.056 0.259 0.138 0.247 0.478 0.568 0.680 0.624 0.652
0.328 0.056 0.260 0.138 0.248 0.478 0.566 0.679 0.626 0.651
0.344 0.053 0.264 0.136 0.257 0.473 0.580 0.668 0.623 0.613
0.319 0.054 0.249 0.142 0.231 0.477 0.571 0.660 0.152 0.592
0.319 0.054 0.250 0.143 0.232 0.478 0.570 0.660 0.161 0.595
6
5
8
9 10
N HCO N HC H CH -4
6
4
3
8
9 10
N HCO N HC H Cl-4
6
4
8
9 10
IIIa N HCS N HC H
6
5
8
9
10
11
*
IIIb N HCS N HC H O CH -4
6
4
3
*
11
For O q = 0.506.
Table 2. Inhibition coefficients and degrees of corrosion protection Z for 08 KP steel in 3 M H SO in the presence
2
4
2
of 1 10 M 1-phenacylmethylpyridinium bromides I III
Z, %
Z, %
Z, %
Z, %
Compound
20 C
40 C
60 C
80 C
Ib [1]
Ic [2]
IIa
IIb
IIc
IIIa
IIIb
23.70
2.60
28.10
30.00
12.75
29.17
39.13
95.78
61.54
96.44
96.67
92.16
96.57
97.44
29.02
4.78
61.83
86.91
22.23
73.54
136.50
96.55
79.08
98.38
98.85
95.50
98.64
99.27
200.32
17.20
517.25
528.56
218.71
634.30
731.85
99.50
94.19
99.81
99.81
99.54
99.84
99.86
144.60
12.00
124.13
210.53
117.97
147.15
162.90
99.30
91.66
99.19
99.53
99.15
99.32
99.39
2
phenylethyl)-2-[3-phenylthiocarbamido]pyridinium
10 4 m , respectively. The steel samples were kept
bromide (IIIa), and 1-(2-oxo-2-phenylethyl)- 2-[3-(4-
in 3 M H SO at 20 C for 24 h, at 40 and 60 C for
2
4
methoxyphenyl)thiocarbamido]pyridinium
IIIb). A mixture of 2-aminopyridine (0.02 M), ap-
propriate isocyanate or thiocyanate, and dioxane
15 ml) was refluxed for 2 h. The reaction mixture
bromide
2 h, and at 80 C for 1 h, and the zinc samples, in
0.5 M H SO at 20 C for 0.5 h. The efficiency of
(
2
4
metal protection was evaluated by the inhibition
(
coefficient
= K /K and degree of protection
M M
was treated with a small amount of water, left over-
night, and then the precipitate was separated. Then,
a mixture containing equimolar amounts (0.0015 mol)
of one of the compounds obtained, -bromacetophe-
none, and 15 ml of ethyl acetate was refluxed for 3 h,
and the precipitate formed was separated. Yields (%)
and boiling points ( C): IIa, 81, 205 207; IIb, 85,
Z = [(K
K )/K ] 100%, where K and KM
M M M
M
2
1
(g m h ) are the gravimetric corrosion indices in
pure and inhibited acid solutions, respectively. Volt-
ammetric measurements with steel and zinc were per-
formed in the potentiodynamic mode after stabiliza-
tion of the free corrosion potential E at a scanning
rate of 2 mV s .
c
1
2
42 244; IIc, 87, 253 255; IIIa, 80, 227 229; and
Quantum-chemical calculations performed by
the procedure from [4, 5] showed that the effective
charges on the nitrogen atom of the amino group
directly bonded to the pyridine ring in ureas II, thio-
ureas III, and compound Ic (Table 1) differ only
IIIb, 80, 220 222, respectively.
The corrosion tests were performed by a com-
mom procedure [1] with 08 KP steel and Ts0 zinc
4
with a working surface area of 14 10 and 5.76
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 12 2006

CORROSION-PROTECTIVE PROPERTIES
1971
+
slightly and are substantially lower than those in Ib.
These results suggest that the inhibiting effect of
the 1-phenacylmethylpyridinium bromides studied
should be close to the effect of Ic and substantially
lower than that of Ib.
where B and B are molecular forms and BH and
s
+
BH , protonated forms in the solution bulk and on
s
the metal surface, respectively. Depending on a partic-
ular metal and on the structure and concentration of
the inhibitor, the above reactions can either accelerate
(
due to easier hydrogen elimination) or decelerate
The results of the corrosion test showed that com-
pounds II and III are efficient inhibitors of steel acid
corrosion (Table 2). The efficiency of the protection
effect substantially increases as temperature is ele-
vated to 60 C. This is in agreement with the hypo-
thesis of specific adsorption of 1-phenacylmethylpy-
ridinium bromides on the surface of steel, developed
in [1, 2, 6]. Ureas (II) and thioureas (III) are charac-
terized by the stronger anticorrosion effect as com-
pared not only to compound Ic, but also to Ib. For
instance, in the presence of IIa and IIIa, for steel
is higher by a factor of 1.2 at 20 C and by a factor of
the corrosion (due to inhibiting effect of protonated
and molecular forms of compounds).
It is known that the discharge of hydroxonium ions
on the zinc surface is characterized by high activa-
tion energy, whereas regeneration of BH +s cations
proceeds fairly rapidly due to the presence of acti-
vated hydrogen ions (H ) in the electric double layer.
Therefore, during zinc corrosion in the acid medium,
the above processes usually decrease the hydrogen
overvoltage and the inhibiting effect of the nitrogen-
containing compounds [7]. On the steel surface, these
processes are complicated, because the activation
energy of the hydroxonium ion discharge on the sur-
+
s
2
.6 and 3.2, respectively, at 60 C than that in the pres-
ence of Ib. Electron-donor groups CH and CH O
3
3
introduced in the p-position of the phenyl ring of IIa
and IIIa enhance the protective properties of these
compounds, whereas the chlorine atom decreases them.
An increase in the temperature to 80 C is accompa-
nied, as for the other compounds of this type, by
a small decrease in the inhibiting effect, probably
caused by desorption of the inhibitor from the metal
surface due to the elevated rate of its dissolution.
The above results show that our compounds are, in-
deed, efficient inhibitors of the steel corrosion, whose
corrosion-protective activity is mainly caused by
the presence of arylurea and arylthiourea groups re-
sponsible for adsorption and inhibition.
face of d metals is relatively low and regeneration of
+
BH is slow due to the ability of nitrogen atoms to
s
interact with unoccupied d orbitals of iron [7]. This
fact accounts for the high inhibiting effect of the com-
pounds studied in the steel corrosion in sulfuric acid
solution and for its substantial decrease in the case of
zinc. For instance, at 20 C in the presence of IIa or
2
IIIa (1 10 M), the rate of steel corrosion decreases
by a factor of 28 and 29, respectively, whereas that of
zinc corrosion, by only a factor of 2.3 (Tables 1, 3).
2
In the presence of Ib (1 10 M) containing amino
group at 20 C, the steel corrosion is inhibited by
a factor of 24, and zinc corrosion, by a factor of 3,
whereas unsubstituted 1-phenacylmethylpyridinium
bromide (Ia) containing no protonation centers in
the pyridinium ring virtually equally inhibits the cor-
rosion of steel [1] and zinc (Table 4).
Being efficient inhibitors of steel acid corrosion,
compounds II and III only slightly inhibit the corro-
sion of zinc in 0.5 M H O , and compound IIIa at
2
4
its low concentrations even stimulates the corrosion
Table 3). The decrease in the protective properties
(
Quantum-chemical calculations showed that
the negative charges on oxygen and sulfur atoms in
of Ia, IIa, and IIIa for zinc, compared to steel, is
probably caused by involvement of these compounds
in catalytic evolution of hydrogen due to discharge
of their protonated forms.
Table 3. Inhibition coefficients and degrees of corrosion
protection, Z, for Ts0 zinc in 0.5 M H SO in the presence
2
4
In accordance with modern views [7], the catalytic
evolution of hydrogen in acid media in the presence
of nitrogen-containing organic compounds capable of
protonation can proceed by the scheme
of 1-phenacylmethylpyridinium bromides IIa and IIIa at
2
0 C
Z, %
Z, %
Concentration,
M
B + H+ = BH+,
BH +s + e = BHs,
BH = B + 1/2H ,
compound IIa
compound IIIa
1
4
10 2
2.34
1.85
1.70
1.62
57.26
45.95
41.17
38.27
2.27
1.80
0.88
0.84
55.94
44.44
3
10
3
1.6 10
s
s
2
6
.4 10 4
+
+
B + H = BH ,
s
s
s
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 12 2006

1972
YURCHENKO et al.
Table 4. Inhibition coefficients and degrees of corrosion
protection, Z, for 08 KP steel in 3 M H SO and for Ts0
thiourea group can decrease, which should facilitate
catalytic evolution of hydrogen on zinc and hence
decrease the protective effect of this group. This as-
sumption is confirmed by the fact that at a concentra-
2
4
2
zinc in 0.5 M H SO in the presence of 1 10
compounds I
M
2
4
3
tion of 1.6 10 M compound IIa increases the over-
Z, %
8 KP Steel
Z, %
voltage of the hydrogen evolution on zinc, whereas
IIIa decreases it (Fig. 1a); compound IIa slightly
inhibits zinc corrosion in 0.5 M H SO , whereas IIIa
R
0
Ts0 Zinc
2
4
H
11.30
23.70
28.10
29.17
91.10
95.80
96.44
96.57
12.52
2.91
2.34
2.27
92.01
65.64
57.26
55.94
stimulates it (Table 3).
H N
2
At the same time, the bulk and surface concentra-
tion of the molecular species of compounds capable
of chemisorption on steel can increase from ureas (II)
to thioureas (III) due to interaction with the metal
surface of their arylurea and arylthiourea groups. This
should inhibit catalytic evolution of hydrogen on
steel and noticeably enhance its protection. This sug-
gestion is in good agreement with the fact that com-
pound IIIa increases the overvoltage of hydrogen
evolution (Fig. 1b) and, correspondingly, is more ef-
ficient inhibitor of steel corrosion than the related urea
IIa (Table 2).
PhNHCONH
PhNHCSNH
the arylurea and arylthiourea groups that can be di-
rectly involved in the protonation amounts to 0.15229,
0
Therefore, in going from urea (IIa) to thiourea (IIIa)
derivatives, the bond strength in the protonated aryl-
.16143 and 0.62322, 0.62615, respectively.
CONCLUSIONS
(1) Arylurea and arylthiourea groups in the pyridi-
nium ring of 1-phenacylmethylpyridinium bromides
are responsible for the high level of their corrosion-
protective effect in steel corrosion in 3 M sulfuric
acid solution at 20 80 C.
(2) The compounds studied are ineffective as in-
hibitors of zinc acid corrosion, which is caused by
catalytic evolution of hydrogen due to discharge of
their protonated species.
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2
3
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Fig. 1. (1 3) Catodic and (1 3 ) anodic polarization curves
recorded (a) on Ts0 zinc in 0.5 M H SO and (b) on 08 KP
2
4
1
steel in 3 M H SO at 20 C in the presence of 1.6 10
M
7. Antropov, L.I. and Pogrebova, I.S., Itogi Nauki, Ser.:
Korroz. Zashch. Korroz., Moscow: VINITI Akad. Nauk
SSSR, 1973, vol. 2, pp. 27 112.
2
4
of compounds IIa or IIIa. (i) Current density and (E) po-
tential. (1, 1 ) none, (2, 2 ) IIa, and (3, 3 ) IIIa.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 12 2006