26 

Al-Khwarizmi 
Engineering   

Journal 

Al-Khwarizmi Engineering Journal,  Vol. 4, No. 4, PP 26-36 (2008) 

 

 

Effect of Chloride Ions on the Corrosion Behavior of Al – Zn Alloy in 

NaOH Solution at Four Different Temperatures 
 

Rana A. Majed ,   Hanaa A. Al-Kaisy  and  Hind B. Al-Atrakchy 
Department of Materials Engineering/ University of Technology 

  

(Received  5 September  2007; accepted  13  May  2008) 

 

 

Abstract 
 

 This research involves study effect of chloride ions in concentration range (0.01 – 0.50 mol.dm
-3

) on the corrosion 

behavior of Al-Zn alloy in basic media of 1x10
-3

 mol.dm
-3

 NaOH at pH=11 and four different temperatures in the range 

(298-313 K). Cathodic and anodic Tafel slopes (bc &ba) and transfer coefficients (αc & αa) were calculated and the 

results interprets according to the variation of the rate – determining steps. The results also indicate that the chloride 
ions are bonded chemically in the interface as an initial step of formation of different mixed oxohydroxy – and chloro 

complexes. Polarization resistance (Rp) is calculates and interprets the different polarization behavior because of 

addition of chloride ions to the basic media. 

 

Keywords: Al-Zn alloy, Effect of chloride ion, Corrosion behavior in basic medium. 

 

 

1. Introduction: 
 

 Corrosion of aluminum has been a subject of 

numerous studies due to the importance of this 
material in contemporary civilization. It is well 

known that there is a potential region in which the 

rate of corrosion, even in such aggressive media 

as chlorides. The relatively complex corrosion 
mechanism of aluminium has been studies by 

several authors. 

 Corrosion of aluminium occurs only when the 
metal protective oxide layer is damaged and when 

the repair mechanism is prevented by chemical 

dissolution[1].  
 Polarization methods have been extensively 

used to investigate the mechanism of localized 

corrosion and processes that lead to localized 

corrosion. In using potentiostatic techniques, the 
potential variable[2]. Potentiostatic and 

potentiodynamic techniques have been applied by 

several authors to study the corrosion of 
aluminium in different environment[3-8]. 

 The exceptional corrosion resistance of 

aluminium in many environments is due to its 

protective oxide film which is relatively inert 
chemically and so provides the passive behavior 

of aluminium.   

 However in aggressive environments, 

particularly in the presence of halide ions, 

aluminium suffers from localized corrosion by 
local breakdown of the passive film. Various 

theories are postulated to explain the mechanism 

of passivity breakdown in halide solutions but the 

most common and accepted ones are as follows: 
a- Penetration theory. 

b- Flaws and crack/heal theory. 

c- Localized acidification theory. 
d- Complex formation theory. 

 

 

2. Experimental Work: 
 

 Al – Zn alloy was cut into cylinder shape with 
(1.2 cm) diameter, and made into electrode by 

pressing a copper wire into a hole on one side and 

then insulating all but one side with an epoxy 
resin. The open side was polished mechanically to 

a mirror finish, rinsed in distilled water and stored 

in a desiccator.  

  The analytical composition of alloy was 
shown in Table (1) which was obtained by 

chemical analysis in Naser Company.                     

  



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 27 

Table  1  

The Analytical Compositions of Al-Zn Alloy Which Useful in This Search. 

Metal  Zn Mg Cu Cr Ni Ti Mn Al 

Wt % 5.70 2.50 1.330 0.22 0.01 0.08 0.06 Bal. 

 
 

 The electrochemical glass cell was of the 

usual type with provision for working electrode 
(Al-Zn alloy), auxiliary electrode (Pt electrode), 

and a Luggin capillary for connection with an 

saturated calomel electrode (reference electrode 

SCE). The basic solution was 1x10
-3

 mol.dm
-3

 
NaOH (obtained by Ferak with M.wt 40 g.mol

-1
 

and purity >99.5%) and distilled water (specific 

conductivity 1x10
-6

 S.m
-1

). To study the effect of 
chloride ions uses NaCl (obtained by Fluka with 

M.wt 58.44 g.mol
-1
 and purity 99.5%) was 

prepared with seven concentrations (0.01, 0.10, 

0.15,0.20,0.25,0.35, and 0.50 mol.dm
-3

). 
 Electrochemical measurements were 

performed with a potentiostat (Corroscript) which 

was obtained from Tacussel (France) at a scan 
rate of 0.3 Volt per minute. 

 The Tafel extrapolation and Linear-

polarization techniques are uses to determine the 
rate of corrosion. The Tafel extrapolation method 

for determining corrosion rate was used by 

Wagnar and Traud to verify the mixed-potential 

theory, the method was shown in figure (1). 
Tangents to the anodic and cathodic Tafel regions 

were extrapolated to the point of intersection, 

from which both the corrosion potentials (Ecorr) 
and corrosion current density (icorr) were 

determine using the four-point method [9] 

cathodic (bc) and anodic (ba) Tafel slopes, 
transfer coefficients (α), polarization resistances 

(Rp) together with other data could be derived 

from the polarization curves by using 

extrapolation method. 
 

 

 

 

 

 

 

 

  

 

   Fig.1.  Tafel Extrapolation Method. 

 

3. Results and Discussion: 
  
 Figure (2) represent the polarization curve of 

Al – Zn alloy in 1x10
-3

 NaOH solution (pH=11) in 

the absence of chloride ions (Cl¯) at 298 K, the 
section (abc) represented the cathodic polarization 

region which occur on the metals presumably by 

migration of electrons through the surface oxide 
films and subsequent interaction of those 

electrons with water molecules and dissolved 

oxygen at the film/solution interface, so the 

corrosion process is complicated with mass 
transfer. Corrosion of Al-Zn alloy proceeds 

similarly by reduction of oxygen and the water 

molecules will act as the electron acceptor and the 
rate of corrosion is controlled by the diffusion 

limited current density for cathodic reduction, the 

probable reactions are: 
 

 Al
3+

   + 3e   →  Al 

 O2  +  2H2O   + 4e ↔ 4OH¯ 
 H2O + e  → 1/2 H2  + OH¯ 
 

 Thus metals like aluminium and zinc, whose 

oxides are amphoteric, are thermodynamically 

unstable in alkaline solutions and will react with 
water at high pHs with consequent hydrogen 

evolution and formation of metal anions as shown 

below:  
 

  Al  + 2H2O → AlOOH  +  3/2 H2 
 

 Along the section (cde), the metal hydroxide 

is expected to be formed. The hydroxide soon 
dissociates into metal oxide (Al2O3) on a surface 

which behaves as a passive layer (protective film) 

according to the reaction: 
 

 Al
3+

  +  3H2O  →  Al2O3  +  6H
+
 

 

 The breakdown of passivity began at point (e) 
and continued along (ef) and this section represent 

the anodic Tafel region.   

 The presence of Cl¯ effects mainly on anodic 

polarization. Fig. (3) show the effect addition of  
0.01mol.dm

-3
 Cl¯ on the corrosion behavior, since 

addition Cl¯ with this concentration penetrates the 

passive layer but partially destroyed and shifts 
passive potential (Epass) to more negative values 

and corrosion current density to lower values. 

      Noble  
 

 

 

 
 

 
       Ecorr 

 

 
 

 
    Active 

A
p

p
li

e
d

 P
o

te
n

ti
a
l 

(E
) 

V
o

lt
 

          icorr 

Log Current Density 
 

     Anodic   

  Curve 

 

 

 

 
  Cathodic        
       Curve 

Linear 

Polarization 

Region 



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 28 

 
 

 

 
  

 

 

 
 

 

 
 

 

 

 
 

 

 
 

 

 
 

 
Fig.2. Polarization Curve for Corrosion of Al-Zn alloy in 1x10

-3
 mol.dm

-3 

NaOH Solution in the Absence of Chloride Ion at 298K. 

 
 

 

 
 

 

 

 
 

 

 
 

 

 

 
 

 

 
 

 

 
 

 

 

 
Fig.3. Polarization Curve for Corrosion of Al-Zn Alloy in 1x10

-3
 mol.dm

-3 

NaOH Solution in the Presence of 0.01 mol.dm
-3

 Chloride Ion at 298K. 
 

 

 
 

 

Current density (A.cm
-2

) 

P
o
te

n
ti

a
l 

(V
o
lt

) 
(S

C
E

) 

a 

b 

c 

d 

e 

f 

 

Current density (A.cm
-2

) 

P
o

te
n

ti
a

l 
(V

o
lt

) 
(S

C
E

) 

a 

b 

c 

d 

e 

f 



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 29 

 When add a higher concentration of chloride 
ion, the passive layer was breakdown and (icorr) 

value increases with increasing the concentration 

of Cl¯ in solution as shown in Figs.(4) to (9) 
where the polarization curve, in general, consist of 

the cathodic (abc) and anodic (cde) Tafel regions.  

 
 

 

 

 
 

 

 
 

 

 

 
 

 

 
 

 

 
 

 

 

 
 

Fig.4. Polarization Curve for Corrosion of Al-Zn Alloy in 1x10
-3

 mol.dm
-3 

NaOH Solution in the Presence of 0.10 mol.dm
-3

 Chloride Ion at 298K. 
 

 
 

 

 

 
 

 

 
 

 

 
 

 

 

 
 

 

 
 

 

 
 

 
Fig.5. Polarization Curve for Corrosion of Al-Zn Alloy in 1x10

-3
 mol.dm

-3 

NaOH Solution in the Presence of 0.15 mol.dm
-3

 Chloride Ion at 298K. 
 
 

 

Current density (A.cm
-2

) 

P
o
te

n
ti

a
l 

(V
o
lt

) 
(S

C
E

) 

a 

b 

c 

d 

e 

 

Current density (A.cm
-2

) 

P
o
te

n
ti

a
l 

(V
o

lt
) 

(S
C

E
) 

a 

b 

c 

d 

e B 

 
 

 

 

A 



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 30 

 
 

 

 
 

 

 

 
 

 

 
 

 

 

 
 

 

 
 

 

 
 

 

 
Fig.6. Polarization Curve for Corrosion of Al-Zn Alloy in 1x10

-3
 mol.dm

-3 

NaOH Solution in the Presence of 0.20 mol.dm
-3

 Chloride Ion at 298K. 
 

 

 
 

 

 

 
 

 

 
 

 

 

 
 

 

 
 

 

 
 

 

 

 
 

 
Fig.7. Polarization Curve for Corrosion of Al-Zn Alloy in 1x10

-3
 mol.dm

-3 

NaOH Solution in the Presence of 0.25 mol.dm
-3

 Chloride Ion at 298K. 
 
 

 

Current density (A.cm
-2

) 

P
o
te

n
ti

a
l 

(V
o
lt

) 
(S

C
E

) 

a 

b 

c 

d 

e 

 

Current density (A.cm
-2

) 

P
o
te

n
ti

a
l 

(V
o

lt
) 

(S
C

E
) 

a 

b 

c 

d 

e 



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 31 

 
 

 

 
 

 

 

 
 

 

 
 

 

 

 
 

 

 
 

 

 
 

 

 
Fig.8. Polarization Curve for Corrosion of Al-Zn Alloy in 1x10

-3
 mol.dm

-3 

NaOH Solution in the Presence of 0.35 mol.dm
-3

 Chloride Ion at 298K. 
 

 

 
 

 

 

 
 

 

 
 

 

 

 
 

 

 
 

 

 
 

 

 

 
 

 
Fig.9. Polarization Curve for Corrosion of Al-Zn Alloy in 1x10

-3
 mol.dm

-3 

NaOH Solution in the Presence of 0.50 mol.dm
-3

 Chloride Ion at 298K. 
 

 

 

Current density (A.cm
-2

) 

P
o
te

n
ti

a
l 

(V
o
lt

) 
(S

C
E

) 

a 

b 

c 

d 

e 

 

Current density (A.cm
-2

) 

P
o
te

n
ti

a
l 

(V
o

lt
) 

(S
C

E
) 

a 

c 

d 

e 

b 



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 32 

 When only hydroxide ions (OH¯) exists in 
solution (NaOH without additive), aluminium 

hydroxide Al(OH)3 will be formed and so 

repairing the passive film on the anode.  
 Moreover the electrolyte at the anode will be 

replenished again with (OH¯) by migration. But 

when Cl¯ exists in solution (NaOH with additive), 

then part of the current will be transported by 
these ions and since the anode products in alkaline 

chloride solution is still Al(OH)3, therefore the 

concentration of chloride ions at the anode will be 
increased rapidly while the concentration of 

hydroxide ions decreases to values corresponding 

to pH values less than (7), solid Al(OH)3 is still 

formed, but finally the electrolyte becomes so 
acid that it leads to the formation of soluble anode 

products rather than solids. 

 This process leads to the breakdown of 
passivity, the reactions may be given by: 

 

 Al →  Al
3+

  +  3e 
 Al  +  3H2O  ↔  Al(OH)3  +  3H

+
 

 

 Under equilibrium condition the rates of 

production and consuming of protons will be 
equal. The proton can be consumed by direct 

reduction: 

 
 2H

+
    +  2e  ↔  H2 

   

 Or by diffusion to the bulk solution: 
 

 H
+

(anode)                     H
+

(bulk solution) 

 

 The results of Ecorr, icorr, bc, ba, αc, αa, Rp, and 
io for Al – Zn alloy in the absence and presence of 

chloride ions in NaOH solution at four different 

temperatures have been given in Table (2). 
 From deep analysis of the cathodic and anodic 

regions of the polarization curves, it was possible 

to derive data concerning: 

a-  The cathodic (bc) and anodic (ba) Tafel slops. 
b- The cathodic (αc) and anodic (αa) transfer 

coefficients. Values of (α) have been 

calculated from the corresponding values of 
the Tafel slope (b) using the relation [10,11]: 

 

 
 

)1...(   
303.2


bF

RT


   
where: 

R: gas constant (8.314 J.mol
-1

.K
-1

). 

T: temperature in Kelvin scale. 

F: Faraday constant (96500). 
 

c- The polarization resistance (Rp) may be defined 

as [12,13, 14]: 
 

)2...(   
)(





di

EEd
R corr

p

   
where E and Ecorr are the applied corrosion 

potential (Volt) respectively, I is the current 

density (A.cm
-2

). 
 For small polarization, one may write 

approximation [13,14]:  

 

)3...(    
)(





corr

corrcorr
p

i

E

di

EEd
R

   

where Ecorr and icorr are the corrosion potential (V) 

and corrosion current density (A.cm
-2
). The ratio 

(Ecorr/icorr) thus corresponds to the resistance of the 

metal/solution interface to charge-transfer 

reaction. It is also a measure of the resistance of 

the metal to corrosion in the solution in which the 
metal is immersed. 

For low-field polarization [15]: 

  

)4...(   
o

Fi

RT

i



 

and 

 

)5...(   
p

ocorr

corr R
Fi

RT

i

E

 

where η=E-Ecorr and io is the equilibrium exchange 

current density (A.cm
-2

). The reaction resistance 
(Rp), which mainly depends upon the equilibrium 

exchange current density (io) determines what 

may be termed the polarizability, i.e., what 
overpotential (η=E-Ecorr) a particular current 

density needs or produces since:  

 

)6...(     
)(

ocorr

corrcorr
p

Fi

RT

i

E

di

EEd

di

d
R 






  

 The polarization resistance (Rp) was also 

determined in another way from Stern- Geary 
equation [16,17,18], where: 

 

)7...(  
)(303.2

0














 corrca

ca

i

p
ibb

bb

di

dE
R  

 

Diffusion 



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 33 

 The values of Rp have been calculated from 
equation (7), which is presented in table (2). 

 The results of Table (2) indicates that the 

lowest value of (b =0.026 or α=2.4) and the 
highest value is (b=0.120 or α=0.5). A cathodic 

Tafel slope of 0.120 (or α=0.5) may be diagnostic 

of discharge-chemical desorption mechanism for 

hydrogen evolution reaction of the cathode in 
which the proton discharge is the rate-determining 

step. If chemical desorption is the rate-
determining step, the rate will then be 

independent on the overpotential since no charge 

transfer occur in such step and the rate becomes 
directly proportional to the concentration or the 

coverage (θ) of the adsorbed hydrogen atoms, and 

may occur at coverage ranging from very small 

values to almost full surface layer formation [19]. 

 

 
 
Table 2 

Values of Corrosion Potential (Ecorr), Corrosion Current Density (icorr), Cathodic and Anodic Tafel Slopes (bc & 

ba), Cathodic and Anodic Transfer Coefficients (αc & αa), Polarization Resistance (Rp), and Equilibrium 

Exchange Current Density (io) for Corrosion of Al-Zn Alloy in 1x10
-3

 mol.dm
-3

 NaOH Solution in Absence and 

Presence of Chloride Ions at Four Different Temperatures. 

Medium 

(mol.dm
-3

) 

T 

(K) 

Corrosion b (V.decade
-1

) α Passivity 

Rp/10
+4

 
io/10

-6
 

(A.cm
-2

) 
-Ecorr 

(Volt) 

icorr/10
-6 

(A.cm
-2

) 
-bc +ba αc αa 

-Epass 
(Volt) 

ipass/10
-5

 

(A.cm
-2

) 

1x10
-3

 

NaOH 

(pH=11) 

only 

298 1.66 2.916 0.107 - 0.55 - 0.99 0.501 14.910 0.172 

303 1.61 3.125 0.100 - 0.60 - 1.20 0.542 13.913 0.187 

308 1.56 3.333 0.095 - 0.64 - 1.22 0.581 13.044 0.203 

313 1.50 3.750 0.091 - 0.68 - 1.24 0.622 11.594 0.232 

pH=11  

+ 

0.01 Cl¯ 

298 1.44 0.416 0.061 - 0.97 - 1.21 0.063 104.52 0.024 

303 1.39 0.500 0.058 - 1.04 - 1.24 0.071 86.956 0.034 

308 1.36 0.541 0.052 - 1.17 - 1.28 0.088 80.366 0.033 

313 1.33 0.625 0.042 - 1.45 - 1.30 0.010 69.565 0.002 

pH=11  

+ 
0.10 Cl¯ 

298 1.39 0.541 0.044 0.120 1.34 0.41 - - 2.584 0.993 

303 1.36 0.583 0.034 0.111 1.76 0.55 - - 1.938 1.346 

308 1.33 0.625 0.031 0.081 1.97 0.75 - - 1.557 1.703 

313 1.31 0.666 0.029 0.062 2.14 1.00 - - 1.288 2.093 

pH=11  

+ 

0.15 Cl¯ 

298 1.38 0.541 0.054 0.115 1.09 0.51 - - 2.949 0.870 

303 1.33 0.583 0.047 0.100 1.27 0.60 - - 2.381 1.096 

308 1.32 0.708 0.029 0.071 2.11 0.86 - - 1.262 2.101 

313 1.31 0.958 0.026 0.051 2.38 1.21 - - 0.780 3.454 

pH=11  

+ 

0.20 Cl¯ 

298 1.39 0.666 0.060 0.120 0.98 0.49 - - 2.607 0.984 

303 1.37 0.833 0.049 0.093 1.22 0.64 - - 1.672 1.560 

308 1.34 0.916 0.042 0.083 1.45 0.73 - - 1.321 2.007 

313 1.32 1.416 0.027 0.068 2.29 0.91 - - 0.592 4.550 

pH=11  

+ 

0.25 Cl¯ 

298 1.39 1.458 0.055 0.100 1.07 0.59 - - 1.056 2.429 

303 1.38 2.000 0.049 0.096 1.22 0.62 - - 0.704 3.706 

308 1.34 2.083 0.045 0.049 1.35 1.24 - - 0.488 5.426 

313 1.33 2.500 0.031 0.036 2.00 1.72 - - 0.289 9.321 

pH=11  

+ 

0.35 Cl¯ 

298 1.38 1.666 0.052 0.057 1.13 1.03 - - 0.708 3.622 

303 1.35 1.875 0.047 0.055 1.27 1.09 - - 0.586 4.447 

308 1.33 3.333 0.046 0.050 1.32 1.22 - - 0.312 8.501 

313 1.32 3.750 0.042 0.042 1.47 1.47 - - 0.243 11.09 

pH=11  

+ 

0.50 Cl¯ 

298 1.39 1.875 0.065 0.091 0.91 0.65 - - 0.878 2.923 

303 1.38 2.242 0.058 0.081 1.03 0.74 - - 0.654 2.988 

308 1.37 3.513 0.051 0.058 1.19 1.05 - - 0.335 7.911 

313 1.36 4.445 0.043 0.037 1.44 1.67 - - 0.194 13.88 

 
 

  

 
 

 

 
 



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 34 

The expected Tafel slope in such step would then 
be -0.03V.decade

-1
 (or =2.0). 

 When electrochemical desorption becomes 

the rate-determining step for the hydrogen 
evolution reaction on the cathode, the expected 

value of bc is -0.05V.decade
-1

 (or α=1.5). 

 The variation of the cathodic and anodic Tafel 

slopes or transfer coefficients may be attributed to 
variation of the rate-determining step in the metals 

dissolution reaction. 

 Another approach to the problem of the 
electrochemical corrosion rate measurement is to 

apply only a small potential difference to the 

specimen and then measure the current density.  

 The measurement of polarization resistance 
has very similar requirements to the measurement 

of full polarization curves and it is particularly 

useful as a method to rapid identifying corrosion, 
up-setting and initiating a remedial action[20]. 

 The results of Table (2) indicates that the 

values of Rp which obtained for the solution at 
pH=11 and in the (pH=11+0.01 mol.dm

-3
 Cl¯) 

system were higher than other media.  

 Generally, the polarization resistance (Rp) in 

the other media decreases with increasing the 
concentration of chloride ion in solution because 

of increases the attack on the bare surface. The 

higher values of Rp enhanced by presence the 
passive layer as shown in the polarization curves 

which attribute to produce aluminium hydroxide 

Al(OH)3 which transform to protective film 
(Al2O3) and reduces the expected attack on the 

surface alloy and lead to more resistance to 

corrosion as shown in Fig.(2), and to the 

equilibrium states between Al2O3 and AlCl3 in 
addition to form Al(OH)3 in (1x10

-3
NaOH + 

0.01Cl¯) system as shown in Fig.(3), but when 

add higher concentrations of Cl¯ there are many 
soluble complexes to be form according to the 

following reactions: 

 

Al  +  3OH¯  → Al(OH)3  +  3e 
Al(OH)3 + OH¯  →  Al(OH)4¯ 

Al(OH)4¯+ Cl¯ →  Al(OH)3Cl¯  +  OH¯ 

Al(OH)3Cl¯+Cl¯ → Al(OH)2Cl2¯ +OH¯ 
Al(OH)2Cl2¯+Cl¯→ Al(OH)Cl3¯ + OH¯ 

Al(OH)Cl3¯  + Cl¯ → AlCl4¯ + OH¯ 

 
 

4. Conclusion: 
 
 From the present measurements the 

conclusion indicates that the polarization behavior 

of Al-Zn alloy in 1x10
-3
 mol.dm

-3
 NaOH solution 

(pH=11) gives special case in the presence of 

1x10
-2
 mol.dm

-3
 Cl¯ and this phenomena may be 

attributed to occur the equilibrium state between 
the Al2O3 and AlCl3 in addition to produce 

Al(OH)3, while the addition of higher 

concentrations of Cl¯ leads to increase the rate of 
corrosion of Al-Zn alloy in the basic media. 

 Chloride ion is bonded chemically in the 

interface as an initial step of the formation of 

different mixed oxohydroxo- and chloro- 
complexes according to the following 

formula[21]: 
 

Al[Ox(OH)y(H2O)z]+Cl¯→ Al[Ox(OH)y-1 Cl(H2O)z    

+ OH¯ 

(AlOOH)4.H2O+ Cl¯→ (AlOOH)3.AlOCl.H2O +  

OH¯ 

AlOOH   +  Cl¯   →  AlOCl   +   OH¯ 

Al(OH)3 +  Cl¯   →  Al(OH)2Cl   +  OH¯ 

 

Finally the [AlCl6]
3-
  complex is produced. 

 The effect of Cl¯ on the polarization curves 
be more significant in the anodic regions, where    

can be observe in Figures (5), (6), and (8) anodic 

polarization observably is marked by two 
important regions, (A) and (B).  

 The region (A) show a gradual increase in the 

current density with applied potential [22]. As 

soon as region (A) is crossed, a sharp rise in the 
current density is observed. This is characteristic 

of region (B).  

 The break in the curve is due to the onset of 
pitting as consequence of breakdown of the oxide 

layer. But in Figures (4), (7) and (9), decease this 

phenomena and the increasing in current density 
is sudden. 

 

 

5. List of Symbols: 
 

b    Tafel slope (V.decade-1) 
E    Potential (Volt) 

F    Faraday constant (96500 C.mol-1) 

i     current density (A.cm-2) 

R    gas constant (8.314 J.mol-1.K-1) 
Rp    polarization  resistance (Ω.cm-2) 

T     temperature (K) 

 
 

6. Greek letters: 
 

α    transfer coefficient  

η    overpotential (Volt) 
 

 



Rana A. Majed                                                         Al-Khwarizmi Engineering Journal, Vol.4, No.4, PP 26-36 (2008) 
 

 35 

7. Sub/superscripts: 
 

a         anodic 

c         cathodic 

corr    corrosion 

pass    passivity 
 

 

8. References:  
 

[1] Roebuck A. H., and Pritchell T. R., Materials 
Protection, July 1966, P.16. 

[2] Sundarrajah J., and Ramchari T., Corrosion, 
17, 1961, P.39-41t. 

[3] Bonewitz R. A., Corrosion-NACE, 29, 1973, 
P.215. 

[4] Bohlmaun E. G., and Posey F. A., Proc. Ist 
Int. Symp. On Water Desalination, 

Washington, D.C., October 1961, P.306. 
[5] Ahmad Z., and Rashidi S., Proc. Third Middle 

East Corrosion Conf., Bahrain, May 16-18, 

1983, P.229-241. 
[6] Nisandoglu K., and Holton H., Corrosion 

Science, 18, 1978, P.835-849. 

[7] Broli A., Holton H., and Sigurdson H., 
Werkstoffe Und Korrosion, 26, 1975, P.629. 

[8] Broli A., and Holton H., 7th Scandinavian, 
"Corrosion Congress", Trondheim, May 1975. 

[9] J. Janko Wisk and R. Juchniewicz, corrosion 
Science, vol.20, P.841, (1980). 

[10] Uhlig H. H., "Corrosion and Corrosion 
Control", Wiley, New York, (2000). 

[11] Sherir L.L.,"Corrosion",Metal/Environment 
Reactions, second ed., 1, 1976, P.4-12. 

[12] Saleh J. M., and Al-Haidari Y. K, Bull. 
Chem. Soc.(Jpn), 62, 1989, P.1237. 

[13] Al-Shamma L. M., Ph.D Thesis, College of 
Science, University of Baghdad, October 

1998. 

[14] Al-Saadie K.A.S., Ph.D. Thesis, College of 
Science, University of Baghdad, October 

1997. 

[15] Goodrad H., Jepson W., Bathwell M. and 
Kane R., "The Corrosion of Light Metals", 

(Wiely, New York), P.1-218, (1967) 

[16] Stern M. and Grary A.L., J. Electrochem. 
Soc., vol.56, P.104, (1957). 

[17] Stern M. and Weisert E.D., Proc. Am. Soc. 
Test Master, vol.59, P.1280, (1959). 

[18] Sykes J.M., Brit. Corrosion J., vol.25, 
P.176, (1990). 

[19] Bockeris J. O. M., and Reddy A. K., 
"Modern Electrochemistry", Press, New 
York, 1970, P.176. 

[20] Fontana G., and Green D., "Corrosion 
Engineering",McGraw–Hill, New York, 

(1978). 
[21] Tomesanyi L., Varga K., Bartik I., Horanyi 

G., and Maleczki E., Electrochimica Acta, 

34, 6, 1989, P.855-859. 
[22] Zaki A., ANTI-Corrosion, November 1986, 

P.4-11. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



 36-26، صفحة 4، اىعذد 4          مجية اىخىارزمي اىهنذسية اىمجيذ                                        رنا عفيف ماجذ                                   
(2008) 
 

 36 

 

زنل  في محيىه هيذرومسيذ -تأثير أيىنات اىنيىريذ عيى سيىك اىتأمو ىسبينة  اىمنيىً

  اىصىديىً عنذ اربع درجات حرارية
 

 رنا عفيف ماجذ      هناء عرير اىقيسي        هنذ باسو األطرقجي
 انجايؼــت انخكُٕنٕجٛــت  /قسـى ُْذسـت انًـٕاد

 

 

 

 اىخالصـــة

( ΣΔ modulator fractional-N يشسهت باسخؼًال يشكب حشدداث يٍ َٕع GaussianFSK انبحث انٗ حصًٛى ٔيحاكاة  ٚٓذف

يذٖ انفصم بٍٛ انقُٕاث  ،(150kb/s)يٛكا ْشحض، َسبت حذفق انًؼهٕياث  ( 900.4 – 869.9) يذٖ انخشدداث انخاسجت: ٔبانًٕاصفاث انخانٛت

(500kHz)،  حقُٛاث انذٔائش .  ْشحض يٍ انخشدد انخاسج10000دٚسبٛم ػُذ  (85-)ياٚكشٔ ثاَٛت ٔيسخٕٖ ضٕضاء طٕس٘  1صيٍ ححٕٚم

خٕاص يثم قهت اسخبذاد انقذسة، صغش انحجى ٔ قهت  .انحذٚثت ساًْج بشكم فاػم فٙ صٚادة انخكايم نهًشسالث ٔانًسخهًاث الشاساث انشادٕٚ

اٌ انخضًٍٛ انًباشش بٕاسطت يشكب انخشدداث يٍ . انكهفت ْٙ انخٙ حؼخبش انًقٛاط انخاص بانخصًٛى ٔانخٙ يٍ خالنٓا ٚخى انحكى ػهٗ اداء انُظاو

 ٔرنك الٌ ْزِ انطشٚقت حؤيٍ انخٕاص انخٙ َحخاجٓا يثم قهت اسخبذاد انقذسة ٔصغش  حى اقخشاحّ فٙ ْزا انبحثΣΔ( Fractional - N)َٕع 

فٙ دٔسة قفم انطٕس انشقًٙ نهسٛطشة ػهٗ انقًٛت انكسشٚت نًقسى انخشدد ٔبٕاسطخّ ٚخى   ٔضؼجΣΔػًهٛت انخضًٍٛ يٍ َٕع  . انحجى ٔقهت انكهفت

انز٘ حى اسخخذايّ نهحصٕل ػهٗ  (Gaussian FSK)َٕع انخضًٍٛ . اصانت انطفٛهٛاث يغ  يسخٕٖ طفٛهٛاث اقم ٔيسخٕٖ ضٕضاء طٕس٘ جٛذ

انسٛطشة ػٍ بؼذ ، اَظًت االياٌ، اٌ انخطبٛقاث نٓزِ انًشسهت ْٙ قهت كهفت َقم انًؼهٕياث انالسهكٙ. كفاءة طٛفٛت ػانٛت فٙ االشاسة انًضًُت

 .ٔانؼذاد انالسهكٙ (RF)بٕاسطت اشاساث