Corrosion Science

‫الحمدُ هلل الذي بنعمته تتم الصالحات ‪ ,‬والصالة والسالم على رسو ِلنا ُمعلم الكــون‪,‬‬
‫ان العلـم نــور ‪ ..‬وبعد‪:‬‬
‫يشكر الناس لم يشكر هللا ‪ ,,‬ونحن نتقدم ببحثِنا هــذا بخالص الشكر‬
‫يُقــال من لم‬
‫ِ‬
‫واالمتنان لكل من ساهم معنا في إنجازه وفي مقدمتهم‬
‫الدكتورة الفاضلة سنـــاء عرب ‪ ،،‬فلقد تعلمنا منها الصبر والدقة و ُحب اإلتقــان‬
‫والكثير الكثيــر فشكـــرا ً لها ‪..‬‬
‫كما ال ننسى أن ن ُخص بال ُ‬
‫شكــر رمزان من ُرموز األخالق قبل العلــم ‪،‬‬
‫دكتورتان يعجز القلم عن وصفهما‬
‫(الدكتورة عائشة التركستاني و الدكتورة عائشة مباركي )‬
‫وتوجيهكم ‪..‬‬
‫فشكرا ً على ُجهدكم‬
‫ِ‬
‫ولكل من حضر المناقشة شكرا ً على الحضور نتمنى ان نقدم ما يحوز على‬
‫رضاكم‪..‬‬
Supervisors by:
Prof. Sanaa T . Arab
By:
Jameelah Hindi Al-sulami
Arwa Marei Al-nahdi
Layla Hussein Ali Hamdi
CONTENTS
1. Introduction
2. Experimental
3. Results and discussion
4. Conclusion
5. References
1.Introduction
1-1 Definition of corrosion and importance of its
study
1-2 Inhibition of Corrosion in Acid Media
1-3 Aluminium Metal
1-4 Corrosion behavior of aluminum
1-5 Some Previous Studies of Aluminium in Acid Solutions
1-6 Aim of the study
1-7 Inhibitor used in the study
Aluminium Metal:
Aluminium, Al, is a metal with a high electronegative potential
(-1.67 V). It is also highly resistant to most acidic and neutral
solutions due to the formation of a protective oxide film on its
surface. This film is responsible for the corrosion resistant of Al
in most environments. Nevertheless, in some cases, Al may be
exposed to high concentrations of acids or bases. These
solutions dissolve the passive film. Under these circumstances,
corrosion inhibitors should be used.
1.Introduction
Definition of corrosion and importance
of its study:
Corrosion is a natural process; it's a result of the inherent
tendency of metals to revert to their more stable compounds,
usually oxides. Most metals are found in nature in the form of
various chemical compounds called ores. In the refining process,
energy is added to the ore, to produce the metal. This is the same
energy that provides the driving force causing the metal to revert
back to the more stable compound.
that is the result of interaction between materials and their
environment.
Aim of the study :
The present work is therefore a new trial
aimed to find a cheap and environmentally
safe inhibitor for aluminium corrosion
inhibition in acidic medium, the use of
buckthorn seeds as safe inhibitor of
aluminium corrosion in HCl solutions .
Inhibitor used in the study:
the fruits of buckthorn are green in the
early stages of composition and then turns
yellow at the completion of growth and
then the Red Vabanny reddish at maturity
and taste of fruit before maturity
overlooked because they contain, within
each there is the fruit of the seed of a
single stone .
2. Experimental
2-1 Materials preparation.
2-2 Preparation of Buckthorn seeds extracts (inhibitor).
2-3 Corrosion Measurements.
• At 30o C .
• At different Temperatures .
2-3-1 Hydrogen Evolution Measurements.
2-3-2 Mass loss Measurements.
2. Experimental
Materials preparation:
Aluminium of the composition (wt %) as : Mn (0.009) , Ni (0.043) , Pb •
(0.014) , Al (95.297) and Fe (0.765) was used for the study. The sample
was polished using a series of emery paper. It washed thoroughly with
deionized water and dried with acetone and with a stream of air.
Preparation of Bukthorn seeds Extracts (Inhibitor):
The fruits of Buckthorn plant was collected from trees in Jeddah city KSA, it
has been purified from the impurities and then washed with water and
left to dry in the air for two days. The aqueous extract extract of the
plant were prepared as follows:
Weight a certain amount (about 50 grams) of dried fruit of the plant
and was crushed in an electric mixer,
then add to it the appropriate (deionized water) and heat
until boiling, the mixture is cooled for 24 hours and then
be feltrated.
Extraction is repeated several times from the same pool,
so extract collect and dried in the air to be concentrated
and deposited to the least possible amount of solvent
used.
The extract was collect after concentrated it and placed in
a standard flask 250 ml capacity and complete to the mark
with the appropriate solvent and therefore is a solution
study.
The study can be divided in two parts:
Part one : at constant temperature (30° C)
Effect of concentration of the studied extract on the corrosion
of aluminum in 0.35 M HCl at 30° C.
The measurements were carried as follows :
Chemical methods.
This method is done in two ways, hydrogen evolution method
(HEM) and mass loss method (MLM).
Hydrogen Evolution Measurements:
Hydrogen evolution measurements were carried out at 30° C, the
clean weighed rod was immersed in the test solution and
immediately the volume of the evolved hydrogen gas was followed
as function of time as described in literature. From the volume of
hydrogen gas evolved per minute, inhibition efficiency (Inh.HE %),
degree of surface coveage (Ө) and corrosion rate (R)
were calculated using equations 1, 2 and 3, respectively:
R(ml min-1cm-1) = (V°Ht-V1Ht) \ t
(1)
Ө = % I / 100
(2)
Inh.HE = 1- (R \ R°) ×100
(3)
Where V1Ht is the volume of hydrogen gas at time t for inhibited solution and V1Ht is the
volume of hydrogen gas evolved at time (t ) for uninhibited solution.
Mass loss Measurements:
The clean weighed rod (W1 )was immersed in the test solution, then after
complete of test , the sample was withdrawn from the tested solution , washed
thoroughly with bi-distilled water followed by acetone and dried with a stream
of air, and reweighed (W2).
From the weight loss results, the inhibition efficiency(% I) of the inhibitor,
degree of surface coverage and corrosion rates were calculated using equations
4,5 and 6, respectively:
∆ W = w1 -w2
R` (g min-1 cm-2) = ∆ W \ A t
Ө = 1 – R \ R°
Inh.ML = (1 – R \ R°) × 100
(4)
(5)
(6)
Part two: at different temperatures.
The effect of temperature and corrosion inhibition on Aluminium
in 0.35 M HCl in absence and presence of Buckthorn.
The study of corrosion inhibition of aluminum in 0.35 M HCl in
absence and presence of the studied extract (at 5 ml.), using
chemical measurements, by hydrogen evolution and mass-loss
30, 40,50,60, and 70° C. methods at
3- Results and discussion
3.1. Effect of concentration of the studied Seeds
Buckthorn extract on the corrosion of aluminium in
0.35 M HCl at 30˚ C.
3.2. The chemical study of aluminium in 0.35 M HCl in
absence and presence of different concentrations of
Seeds Buckthorn at 30˚ C is carried out.
Effect of concentration of the studied Seeds
Buckthorn extract on the corrosion of aluminium
in 0.35 M HCl at 30º C.
The chemical study of aluminium in 0.35 M HCl in
absence and presence of different concentrations of
Seeds Buckthorn at 30º C is carried out.
5
Col
Col
Col
Col
Col
Col
Col
Col
Col
V/A
hydrogen evolution
( ml cm-2 )
4
3
3- Results and discussion
1
1
1
1
1
1
1
1
1
vs
vs
vs
vs
vs
vs
vs
vs
vs
Col
Col
Col
Col
Col
Col
Col
Col
Col
2
3
4
5
6
7
8
9
10
2
1
0
0
20
40
60
80
t (min)
Fig (1): Volume of hydrogen\ time curves of aluminium corrosion in 0.35 M HCl
in absence and presence of different concentrations of Buckthorn at 30° C.
100
The figure also, reveals that the increase in the concentration of correlates with a decrease in the
slope of the straight lines of the curve i.e. increases the inhibition efficiency. This means that the
presence of studied extract in the medium retards the corrosion of Aluminium in 0.35 M of HCl (in the
range 0.5 - 10), and the extent of inhibition of corrosion depends on the concentration of the extract in
the acid. The rate, then increases with higher concentrations, this may be attributed to the formation of
soluble compound.
Inspection of table (1) shows that the data obtained from hydrogen evolution are in agreement with
those obtained from mass loss measurements especially at high concentrations. The inhibition
percentages were calculated from hydrogen evolution (Inh. HE %) and mass loss (Inh. ML %)
measurements using equations (3) and (6):
C
MLM Method
HEM Method
R x 105
Inh %
R x 103
Inh %
0.0
1.9981
-------
22.48
-------
0.5
1.3792
30.97
19.79
13.00
1
1.2638
36.75
17.66
21.46
43.65
11.82
47.43
2
1.1259
3
0.35321
82.32
5.23095
76.73
5
0.36362
81.80
4.0372
82.04
10
0.39515
80.22
5.6
75.09
11
0.81460
59.23
10.709
52.36
Table (1) Percentage of inhibition at different concentrations of Seeds Buckthorn extract
from hydrogen evolution (Inh.HE %) and mass loss (Inh.ML %) measurements.
In Fig (2), the inhibition efficiency Inh. % of the extract is described. An
increase with increasing the extract concentration, then a decrease in the
inhibition is found.
100
80
inh %
60
40
20
c vs inh HE
c vs inh ML
0
0
2
4
6
8
10
12
C
Fig (2): The relationship between Inh. % and the concentration
of the extract deduced from the two chemical methods.
The inhibition efficiency increase is proposed to form an insoluble complex
adsorbed on aluminium surface, leading to more inhibition efficiency, this
complex may leads to blocking most of the active centers on aluminium surface,
thereby increasing the surface coverage, while the decrease explained to be due
to the formation of a soluble complex, leading to more dissolution of aluminium
and an acceleration of the corrosion rate.
Langmuir adsorption isotherm can be expressed as:
The adsorption isotherm obtained for the studied extract is plotted in Fig (3).
14
12
C/
10
8
6
c vs C / Q HE
c vs C / Q ML
Plot 1 Regr
4
2
2
4
6
8
10
12
C
Fig. (3) Langmuir isotherm adsorption model
Of the Aluminium surface of inhibitor in 0.35 M HCl.
The calculated values of K and ΔG°ads. were found to be 2.46 and -33.78k.J. mol.-1 from the
hydrogen evlution method and , the values 6.03and -34.17 k.J. mol-1 from mass loss method ,
respectively, this is in agreement with that obtained in previous studies.
Table (2). Regression coefficient, slope, adsorption constants (Kads) and
free enrgy of adsorption (∆G°ads) obtained from Langmiur isotherm for
extract in 0.35 M HCl at 30°C.
-∆Gads (K.J)
r²
Slope
Kads
HE
0.9967
1.3633
2.46
33.78
ML
0.9999
1.2622
6.03
34.17
Kads. =
1
55.5
exp (- ΔG°ads./ RT )
The effect of temperature and corrosion inhibition on Aluminium in
0.35 M HCl in absence and presence of Buckthorn.
The study of corrosion inhibition of Aluminium in 0.35 M HCl in absence and presence of
Buckthorn (5 ml) using chemical measurements were carried out by hydrogen evolution
and mass-loss methods at 30,40,50,60 and 70° C.
Figures (4, 5) show the effect of temperature on the volume of
hydrogen evolved in 0.35M HCl in absence and presence of Buckthorn.
-2
volume of hydrogen V/A ( ml cm )
16
t(min)
t(min)
t(min)
t(min)
t(min)
14
12
vs
vs
vs
vs
vs
30
40
50
60
70
10
8
6
4
2
0
0
20
40
60
80
100
T (min)
Fig (4): Volume of hydrogen/time curves of Aluminium in 0.35 M HCl
(Free acid) at different temperatures in absence of Buckthorn.
Volume of hydrogen V/A (ml cm-2 )
18
t(min)
t(min)
t(min)
t(min)
t(min)
16
14
vs
vs
vs
vs
vs
30
40
50
60
70
12
10
8
6
4
2
0
0
20
40
60
80
100
T (min)
Fig (5): Volume of hydrogen/time curves of Aluminium in 0.35 M HCl
in presence of (5 Ml) in Buckthorn at different temperatures.
The relationship between the volume of hydrogen rise over time in the
absence and the presence of the studied extract at temperatures : 30,
40, 50, 60 and 70° C are shown in Figure (6) .
1.6
1.4
V/A
hydrogen evolution
( ml cm-2 )
1.2
1.0
0.8
0.6
0.4
0.2
t vs inh 30
t vs free
0.0
0
20
60
40
80
100
t (min)
Fig. (6): Volume of hydrogen/time curves of Aluminium in 0.35 M HCl
in the absence and presence of (5 Ml) in Buckthorn at temperature 30° C .
10
14
12
V/A
hydrogen evolution
( ml cm-2 )
V/A
hydrogen evolution
( ml cm-2 )
8
6
4
2
t(min) vs v/a (free)
t(min) vs Inh(5)
0
0
20
40
60
80
10
8
6
4
2
t(min) vs v/a (free)
t(min) vs Inh(5)
0
100
0
10
20
30
40
50
60
70
t (min)
16
18
14
16
14
12
V/A
hydrogen evolution
( ml cm-2 )
V/A
hydrogen evolution
( ml cm-2 )
t (min)
10
8
6
4
12
10
8
6
4
t(min) vs v/a (free)
t(min) vs Inh(5)
2
t(min) vs v/a(free)
t(min) vs Inh(5)
2
0
0
0
10
20
30
40
t (min)
50
60
70
0
10
20
30
40
50
60
70
t (min)
Fig. (6): Volume of hydrogen/time curves of Aluminium in 0.35 M HCl
in the absence and presence of (5 Ml) in Buckthorn at temperature 40, 50 , 60
and 70° C .
100
80
60
inh %
40
20
0
-20
-40
t vs HE
t vs ML
-60
-80
20
30
40
50
60
70
80
o
t C
Fig. (7): Variation of inhibition efficiency with temperature
for the dissolution rate of Aluminium in 0.35M HCl.
Table (3): The variation of inhibition percentage with temperature
from two chemical methods (HEM) and (MLM).
temperature
%Inh.MLM
Inh.HEM%
30
81.86
82.04
40
48.20
20.88
50
-11.86
-1.66
60
19.20
9.09
70
15.51
8.73
Table (4) : Activation parameters for Aluminium corrosion in 0.35
M HCl in absence and presence of ( 5 Ml ) of Buckthorn extract at
different temperatures.
ΔE(kJ.mol-1)
ΔH(kJ.mol-1)
-ΔS(J.mol-1K -1)
Free acid
0.044
0.16
85.60
%Inh.ML
0.074
0.23
85.50
%Inh.HE
0.072
0.25
85.48
0
log R
-1
-2
-3
1000 / T vs log R (ml)
1000 / T vs log R(HE)
1000 / T vs log R
Plot 1 Regr
-4
-5
2.8
2.9
3.0
3.1
3.2
3.3
3.4
1000 / T
Fig. (8): Arrhenius plots for Aluminium corrosion in 0.35 M HCl in absence
and presence of (5 M) of Buckthorn extract at different temperatures.
0.000
-0.002
log R / T
-0.004
-0.006
-0.008
-0.010
1000 / T vs log R / T (ML)
1000 / T vs log R / T (HE)
1000 / T vs log R / T
Plot 1 Regr
-0.012
-0.014
2.8
2.9
3.0
3.1
3.2
3.3
3.4
1000 / T
Fig. (9): Variation of log (R\T) vs.1T for Aluminium in 0.35 M HCl in absence
and presence of (5 M) of Buckthorn extract at different temperatures.
Conclusion:
The Following results can be drawn from
this study:
1- Buckthorn seeds are an effective
inhibitor of corrosion of aluminium in
0.35 M of HCl solutions at 30° C.
2-The inhibition efficiency of the extract
giave an increase with increasing the
extract concentration, then a decrease
in the inhibition is found at higher
concentrations of it.
3- The inhibition efficiency increase is proposed to be
due to the formation of an insoluble complex
adsorbed on aluminium surface, leading to more
inhibition efficiency, this complex may leads to
blocking most of the active centers on aluminium
surface, thereby increasing the surface coverage,
while the decrease explained to be due to the
formation of a soluble complex, leading to more
dissolution of aluminium and an acceleration of the
corrosion rate.
4- The results show linear correlation coefficients close
to one, which confirms that the adsorption of the
extract components on the surface of aluminium
sample under study is the basic step in the process of
5- The negative value of ΔG°ads.
indicates that the adsorption process
of inhibition on aluminum surface is
spontaneous.
6-The obtained results from the two
chemical studied methods are in
good agreement.
7- The effect of temperature on the inhibition of aluminium in 0.35
M HCl in presence of (5 Ml) in Buckthorn at temperature 30, 40,
50, 60 and 70° C can be summarized as follows:
1. At 30° C the inhibition of corrosion was
high.Adsorption
of extract components on aluminium surface was
.
according to Langmiur adsorption isotherm which was suggested
to be physical adsorption.
2. At 40 ° C, decreasing of inhibition is found.
3. At 50° C , the surface of aluminium metal become partially
uncovered leading to perform large cathodic area and small anodic area
,so ,dissolution of aluminium become very high , acceleration of
corrosion is obtained.
4. At 60 and 70° C, aluminium surface becomes uncover,
since no more of the extract components on aluminium surface
will be found. The dissolution of aluminium will continue with
normal rate.
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