Corrosion Inhibition of Water Hyacinth Leaves, Zn and … Inhibition of Water... · Corrosion inhibition of Water Hyacinth leaves extract ... The results such as Tafel slopes,

Inhibition by Water Hyacinth Leaves, Zn2+ and TSC Kavitha et al.

Corrosion Inhibition of Water Hyacinth Leaves, Zn2+

and

TSC on Mild Steel in neutral aqueous medium

N. Kavitha [a]*, P. Manjula [b]

Corrosion inhibition of Water Hyacinth leaves extract (WHLE) - Zn2+ - TSC in aqueous environment containing 60

ppm Cl- ion on mild steel are studied. The investigations revealed that 25 ppm of TSC acts as an efficient synergist

in corrosion inhibition process. Maximum inhibition efficiency of 95% was obtained for the ternary formulations of

0.1% (v/v) WHLE – Zn2+(50 ppm) – TSC (25 ppm). The Potentiodynamic polarization study showed that the

formulations control anodic reactions predominantly

Keywords: weight loss method, synergism, TSC

* Corresponding Authors

[a] A.P.A.College of Arts and Culture, Palani-624 601,Dindigul district,Tamil Nadu,India.

Email: [email protected].

[b] A.P.A.College for Women, Palani, Dindigul district,Tamil Nadu,India.

1. INTRODUCTION

Many synthetic compounds have shown good corrosion inhibition property, but most of them are highly toxic, expensive, and dangerous to human being and environment [1]. This will lead us to search environment- friendly, cheap, renewable green corrosion inhibitors. Several studies have been carried out on the inhibition of corrosion on metals such as, garlic extract[2], C.Papaya leaves [3], Spirulina[4], Beet root[5], Banana peel [6], Aloes extract [7], and Phyllanthus Amarus extract [8], etc., Like that Water Hyacinth ( Eichorrnia Crassipes), a abundant noxious fresh water weed [9] was found that as a good corrosion inhibitor due to the presence of anti oxidants of chlorophylls, carotenoids, phenols, alkaloids, and terpenoids in their extracts showed corrosion inhibition efficiency on magnesium alloy [10], on mild steel in HCl solutions [11] and the corrosion inhibition of Eichorrnia Crassipes leaves extract in marine environment for AISI 1030 steel was examined using weight loss and electrode potentials techniques[12]. In this research work, the corrosion inhibitory effects are studied for the new ternary inhibitor formulation containing Water Hyacinth leaves extract (WHLE) -Zn

2+ and Tri Sodium

Citrate (TSC) in aqueous medium containing 60 ppm Cl- ion.

2. EXPERIMENTAL

2.1. Preparation of the Specimen

Mild steel specimens of size 1.0 cm ×4.0 cm ×0.2 cm and chemical composition 0.026 % sulphur,0.06 % phosphorous, 0.4 % manganese, 0.1% carbon and the rest iron were polished to a mirror finish and degreased with acetone and used for the weight loss method and surface examination studies.

2.2. Weight-Loss Method

Mild steel specimens were immersed in 100 ml of the aqueous medium containing 60 ppm Cl- ions in

various Concentrations of the inhibitor WHLE in the absence and presence of Zn2+

and TSC for one day. The Inhibition efficiency (IE %) was calculated using the equation,

Int. J. Nano. Corr. Sci. Engg. 1(1) (2014) 31

E-ISSN: 2395 - 7018


Inhibitonefficiency,

Surface coverage,

Where Wo and Wi are the weight loss for mild steel in the absence and presence of inhibitor.

2.3. Determination of corrosion Rate

The corrosion rate (CR) is directly proportional to the weight loss / cm2 in a specified time and was

calculated by the formula,

Where, W = weight loss in mg.

D = density of mild steel (7.85 g / cm2 for mild steel),

A = Area in cm2,

T = Exposure time in hours,

Trends of CR and IE are graphically evaluated.

2.4. Calculation of synergistic factor (SӨ)

These spectra were recorded in a Perkin-Elmer-1600 spectrophotometer using KBr pellet. The FTIR spectrum of the protective film was recorded by carefully removing the film, mixing it with KBr, and making the pellet.

Where ϴA and ϴB are the surface coverage of compounds A and B respectively, acting alone and ϴAB is the experimentally observed combined surface coverage of the solution containing both A and B.

2.5. Analysis of Variance (F-Test)

An F-test was carried out to investigate whether the synergistic effect existing between inhibitor systems is statistically significant [13,14]. If F-value is greater than 5.99 for 1,6 degrees of freedom, the synergistic effect proves to be statistically significant. If it is less than 5.99 for 1,6 degrees of freedom, it was statistically insignificant at a 0.05 level of significance.

2.6. Polarization and AC Impedance

Polarisation studies were carried out in a CHI- electrochemical work station with impedance model 760D. The results such as Tafel slopes, Icorr and Ecorr were calculated. The instrument used for polarisation was used for AC impedance study also. The values such as charge transfer resistance, Rct and the double layer capacitance, Cdl were calculated.



3. RESULTS AND DISCUSSION

3.1. Weight loss method

3.1.1. Influence of TSC on the IE of WHLE – Zn

2+

From table 1, it is seen that the concentration of 25 ppm TSC and 50 ppm Zn2+ provides 23% and 50% IE respectively, in 60 ppm Cl- containing aqueous corrosive medium. In the case of binary system containing 0.1% (v/v) WHLE and 50 ppm Zn2+ has 87% IE [15] which is increased to 95% by the addition of 25 ppm TSC. Figure 1 shows the increase inhibition efficiency of various concentrations of WHLE and 50 ppm of Zn2+ in the presence of 25 ppm of TSC.

Table.1. Corrosion rate (CR) and Inhibition efficiency (IE) of mild steel immersed in 60ppm Cl- containing aqueous medium by weight loss method

Immersion period: One day

Inhibitor formulations

CRx103

mmpy

Surface Coverage (θ)

Inhibition efficiency (%) WHLE

% (v/v)

Zn2+ (ppm)

TSC (ppm)

0 0 0 139.49 - -

0 0 10 116.24 0.1667 17

0 0 15 113.92 0.1833 18

0 0 25 106.94 0.2333 23

0 10 0 83.694 0.4000 40

0 25 0 79.044 0.4333 43

0 50 0 69.745 0.5000 50

0.025 0 0 102.29 0.2667 27

0.05 0 0 88.344 0.3667 37

0.075 0 0 65.096 0.5333 53

0.1 0 0 55.796 0.6000 60

0.025 50 0 46.497 0.6666 67

0.05 50 0 23.248 0.8333 83

0.075 50 0 20.924 0.8500 85

0.1 50 0 18.598 0.8667 87

0.025 50 25 16.27 0.8833 88

0.05 50 25 15.34 0.8900 89

0.075 50 25 13.95 0.9000 90

0.1 50 25 6.97 0.9500 95



Figure 1: Various Concentration of WHLE on the Inhibition efficiency (%) of Zn2+ (50 ppm) and TSC (25 ppm)

3.1.2. Effects of concentration on corrosion rate

As shown in figure 2, it was observed that the rate of corrosion of mild steel decreases with increase of various concentrations of WHLE - Zn

2+ (50 ppm) and 25 ppm of TSC, indicating that the aqueous extracts of

WHLE inhibited the corrosion of mild steel in aqueous medium containing 60ppm Cl-ion.

Figure 2: Various Concentration of WHLE on the CR (mmpy) of Zn2+ (50 ppm) and TSC (25ppm)

3.2. Synergism parameters

Synergism parameters are indications of synergistic effect existing between two inhibitors [16,17]. Synergistic factor (SӨ) is calculated for the mixture containing various concentrations of WHLE & Zn

2+

(50ppm) as A and TSC (25 ppm) as B.

Where A and B are the surface coverage of compounds A & B respectively, acting alone and AB is the experimentally observed combined surface coverage of the solution containing both, A and B. If inhibitors, A and B have no effect on each other & adsorb at metal –solutions interface independently, then the value of synergistic factor, SӨ=1. When the value of Sϴ >1, shows synergistic effect and S<1 shows antagonistic effect



between the inhibitors. The values of synergism parameters (Table 2)are greater than one, indicating synergistic effect existing between various concentrations of WHLE - Zn

2+ (50 ppm) and 25 ppm of TSC.

Table 2. Synergism parameters of IE of WHLE – Zn2+ - TSC

Binary mixture: Various concentrations of WHLE+ Zn2+ (50 ppm)

Binary mixture

TSC (θ) Sθ

0 ppm 25 ppm

0 - 0.2333 -

0.025 0.6666 0.8833 2.190

0.05 0.8333 0.8900 1.1619

0.075 0.8500 0.9000 1.1501

0.1 0.8667 0.9500 2.0440

3.3. Analysis of Variable (Anova) (F- test)

F- Test was carried out between various concentrations of WHLE and various concentrations of WHLE - Zn

2+ (50 ppm) and 25 ppm of TSC. The calculated F-value is 36.47 is statistically significant, since it is greater

than the critical F-value (5.99) for 1,6 degrees of freedom of 0.05 level of significance. Hence, it is concluded that the inhibition efficiencies of the WHLE - Zn

2+ - TSC system is statistically significant as in Table 3.

Table 3. Distribution F-value between the inhibition efficiencies of various concentrations of WHLE and various concentrations of WHLE - Zn2+ (50 ppm) and 25 ppm of TSC

Source of variance Sum of

squares

Degrees of

freedom

Mean

square

F Level of

significant of F

Between 4278.12 1 4278.12

36.47 P> 0.05

Within 703.75 6 117.29

3.4. Analysis of Polarisation Curves

The Potentiodynamic polarisation curves of mild steel immersed in various test solutions are shown in Figure 3. The corrosion parameters are shown in Table 4. When the mild steel is immersed in 60 ppm of Cl

- ion

containing aqueous medium, the corrosion potential is – 550 mV vs SCE. But the formulation of 0.1% (v/v) WHLE + 50 ppm of Zn

2+ + 25 ppm of TSC shift the corrosion potential to -433 mV vs SCE. This suggests that

anodic reaction is controlled predominantly [18]. Due to the addition of of 0.1% (v/v) WHLE + 50 ppm of Zn2+

+ 25 ppm of TSC the corrosion current is shifted from 101.2 µA / cm

2 to 12.28 µA / cm

2 and the LPR value

increased from 456 ohm cm2 to 3465.8 ohm cm

2. This indicates that the protective film is formed on the metal

surface [19].


(a) (b) Figure 3. Polarisation curves of mild steel immersed in various test solutions a) 60 ppm Cl- ion(blank) b) 60 ppm Cl- ion +

WHLE 0.1%(v/v) + 50 ppm Zn2+ion + 25 ppm of TSC.

Table 4. Corrosion parameters of mild steel immersed in 60 ppm Cl- containing aqueous medium in the presence and absence

of inhibitor system by polarization study

System -Ecorr

mV vs SCE

bc

mV / decade

ba

mV / decade

LPR

Ohm cm2

Icorr

µA / cm2

IE

(%)

Blank:

60 ppm Cl- containing

aqueous medium

550 187 245 456 101.2 -

60 ppm Cl- ion

+WHLE0.1%(v/v) +

50 ppm Zn2+ + 25

ppm TSC

433 190 202 3465.8 12.28 88

3.5. Analysis of AC impedance spectra

The AC impedance spectra spectra of mild steel immersed in various test solutions were shown in Figure 4. The AC impedance parameters, such as charge transfer resistance (Rt) and double layer capacitance (Cdl) were given in Table 5. In the presence of 0.1% (v/v) WHLE + 50 ppm of Zn

2+ + 25 ppm of TSC the Rt value increased

from 968 ohm cm2 to 2109 ohm cm

2 and the Cdl value decreased from 4.433x10

-7 F cm

-2 to 2.0346x10

-7 F cm

-7.

This concludes that a protective film is formed on the metal surface. This is further supported by the increase in impedance value log (Z / ohm) (Bode plot) from 3.081 to 3.371 and the increase in phase angle value of 58.37

0

to 61.650 (Figure 5). This confirms the good Inhibition efficiency of 0.1% (v/v) WHLE + 50 ppm of Zn

2+ + 25

ppm of TSC system [20].

Table 5. Corrosion parameters of mild steel immersed in 60 ppm Cl- containing aqueous medium in the presence and

absence of inhibitor system by AC impedance spectra.

System

Nyquist plot

Bode plot

Rt ohm cm2 Cdl

F /cm-2

Impedance

value log (Z /

ohm)

Phase angle deg(0)

Blank:

60 ppm Cl- containing aqueous medium

968

4.4334

x10-7

3.081

58.37

60 ppm Cl- ion + WHLE0.1%(v/v) +

50ppmZn2+ion+25 ppm TSC

2109 2.0346x 10-7 3.371 61.65


Int. J. Nano. Corr. Sci. Engg. 1(1) (2014)

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(a) (b)

Figure 4. AC impedance spectra of mild steel immersed in various test solutions a) 60 ppm Cl- ion(blank) b) 60 ppm Cl- ion

+ WHLE 0.1%(v/v) + 50 ppm Zn2+ + 25 ppm TSC.

(a)

(b)

Figure 5. AC impedance spectra of mild steel immersed in various test solution (Impedance – Bode plot ) a) 60 ppm Cl-

ion(blank) b) 60 ppm Cl- ion + WHLE 0.1%(v/v) + 50 ppm Zn2+ + 25 ppmTSC.

4. CONCLUSIONS

The present study leads to the following conclusions:

The ternary formulations of 0.1% (v/v)WHLE - Zn2+

(50ppm) – TSC (25 ppm) provide 95% inhibition

efficiency to mild steel immersed in aqueous medium containing 60ppm of Cl- ion.

Synergistic effect exists between WHLE - Zn2+

and TSC.


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AC impedance spectra prove that a protective film is formed on the metal surface.

The ternary formulation controls the anodic reaction predominantly.

REFERNCES

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[9] B. Gopal, Water Hyacinth: Aquatic plant studies 1.New York: Elsevier Science Publishing Company; 1987.

[10] SMM Shanab, MA Ameer, AM Fekry, AA Ghoneim and EA Shalaby, Int. J. Electrochem. Sci., 6 (2011), 3017 -3035.

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[14] R.Epshiba, A.Peter Pascal Regis, and S.Rajendran, Int. J. Nano. Corr. Sci. Engg. 1(1) (2014), 1-11.

[15] N. Kavitha, P.Manjula and K. Jeevanantham, Reseaerch Desk, 3(1) (2014), 400-409.

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Received: (30-09-2014) Accepted: (07-11-2014)


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Corrosion Inhibition of Water Hyacinth Leaves, Zn and … Inhibition of Water... · Corrosion inhibition of Water Hyacinth leaves extract ... The results such as Tafel slopes,