Cuminum cyminum Extracts as Eco-Friendly Corrosion Inhibitor for Mild Steel in Seawater

e inhibitive effect of Jeera (Cuminum cyminum) plant extracts on the corrosion of mild steel in an aqueous solution of seawater was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques.e stability of the inhibition efficiency of Jeera extracts was examined by weight-loss method. Potentiodynamic polarization curves indicated that the Jeera extract behaves as an anodic type inhibitor. EISmeasurements showed that the dissolution process occurs under activation control. e corrosion rates of steel and the inhibition efficiencies of the extract obtained from impedance and polarization measurements were in good agreement. Inhibition was found to increase with an increasing concentration of the plant extract. e results obtained show that the Jeera extract could serve as an effective inhibitor for the corrosion of mild steel in seawater.


Introduction
Recently, plant extracts have again become important as an environmentally acceptable, readily available, and renewable source for a wide range of needed inhibitors.Plant extracts are viewed as an incredibly rich source of naturally synthesized chemical compounds that can be extracted by simple procedures with low cost.However, synergistic (and antagonistic) effects are oen expected with these mixtures of inhibitors that may affect their inhibition efficiency.Several investigations have been reported using such economic plant extracts.El Hosary et al. [1] studied the corrosion inhibition of aluminium and zinc in 2 N HCl using naturally occurring Hibiscus sabdariffa (Karkade) extract.e inhibition of corrosion of steel, aluminium, and copper in HCl, H 2 SO 4 , and citric acid by molasses was also studied [2], and 83% and 13% inhibition efficiencies were obtained for HCl and H 2 SO 4 solutions, respectively, containing 0.75% molasses.Loto reported the inhibitive action of Vernonia amygdalina (bitter leaf) on the corrosion of mild steel in 0.5 M HCl at 28 ∘ C [3]. Avwiri and Igho studied the inhibitive action of V. amygdalina on the corrosion of aluminium alloys in HCl and HNO 3 at concentrations of 0.2 and 0.4 g/L at 29 ∘ C [4].ey showed that the solution extract of the leaves serves as an excellent inhibitor.e inhibition effect of Zanthoxylum alatum plant extract on the corrosion of mild steel in 20%, 50%, and 88% aqueous orthophosphoric acid has been investigated by weight loss and electrochemical impedance spectroscopy (EIS).Plant extract was found to reduce the corrosion of steel more effectively in 88% than in 20% phosphoric acid [5].An inhibition efficiency of 75.11% was observed with the extract of the leaves of Nypa fruticans Wurmb [6] for the corrosion of mild steel in hydrochloric acid solutions.El-Etre et al. examined some naturally occurring substances as corrosion inhibitors for different metals in various environments [7][8][9][10][11].
Guar gum was analyzed for its anticorrosion activity by Abdallah [33].Martinez and Stern have studied the inhibitory mechanism of low carbon steel corrosion of mimosa tannin in H 2 SO 4 media [34].Oguzie investigated the efficiency of Telfairia occidentalis extract as corrosion inhibitor in both HCl and H 2 SO 4 media [35].e extracts of chamomile, halfabar, black cumin, and kidney bean were analyzed for their inhibitive action of corrosion of steel in acid media by Abdel-Gaber et al. [36].El-Hosary et al. [37] studied the corrosion inhibition of aluminium and zinc in HCl using Hibiscus sabdariffa extract.Rajendran et al. [38,39] studied the corrosion inhibition of aluminium in rain water containing garlic extract.Aqueous extracts of rhizome powder [40], beet root extract [41], and Hibiscus rosa-sinensis have been used as corrosion inhibitors.e present work is to examine the aqueous Jeera extract as an inhibitor for corrosion of carbon steel in solutioncontaining seawater.Weight loss measurements, potentiodynamic polarization, �uorescence, and �V-spectroscopy are used to study surface �lm formed on the metal surface.

Preparation of Plant Extract of Jeera
Extract.An aqueous plant extract was prepared by grinding 10 g of (Cuminum cyminum) extract, �ltering, and making up to 100 using double distilled water.

Weight Loss Method.
Relevant data of seawater used in the study are given in Table 1.
Carbon steel specimens in triplicate were immersed in 100 mL of the solutions containing various concentrations of the inhibitor for one day.e weight of the specimens before and aer immersion was determined using Shimadzu balance, model AY 62. e corrosion products were cleansed with Clarke's solution [42].e inhibition efficiency (IE) was then calculated using where  1 = corrosion rate in the absence of the inhibitor, and  2 = corrosion rate in the presence of the inhibitor.
2.4.Surface Examination.e carbon steel specimens were immersed in various test solutions for a period of one day, taken out, and dried.e nature of the �lm formed on the surface of metal specimens was analyzed by FTIR spectroscopic study.
2.4.1.FTIR Spectra.FTIR spectra were recorded in a Perkin-Elmer 1600 spectrophotometer.e �lm was carefully removed and mixed thoroughly with KBr made in to pellets, and FTIR spectra were recorded.e �uorescence spectra of the �lm formed on the CS samples recorded with a Hitachi F-4500 �uorescence spectrophotometer.

Potentiodynamic Polarization.
A three-electrode cell consisting of mild steel as working electrode (WE), a platinum wire counter electrode (CE), and a saturated reference electrode was used for measurements.All the potential values reported here were VS SCE.e working electrode was mechanically polished on various grades of emery sheet, rinsed with double distilled water, and degreased with trichloroethylene.Potentiodynamic polarization curves were recorded using an H and CH electrochemical work station impedance analyzer model CHI 660A provided with iR compensation option.Polarization curve measurements were carried out at scan rate of 0.01 V s −1 .e exposed area (1 cm 2 ) was mechanically polished with a series of emery sheets of variable grades.e samples were washed thoroughly with double distilled water before insertion in the cell.During the polarization study, the scan rate was 0.01 V s −1 , hold time at Ef was 0 s, and quiet time was 2 s.
2.6.Ac Impedance Measurements.e instrument used for polarization was used for AC impedance study also.e cell set-up was the same as that had been used for polarization measurements.e real part and imaginary part of the cell impedance were measured in ohms at various frequencies.e values of charge transfer resistance,  ct , and the double layer capacitance,  dl , were calculated.e equivalent electrical circuit diagram is shown in Figure 7.  concentration of Jeera extract was increased, the inhibition efficiency decreased, and the corrosion rate increased, and this is due to the fact that when higher concentrations of Jeera extract are added, the protective �lm (Fe 2+ -Cuminum cyminum complex) formed on the metal surface goes in to the solution and thus destroying the protective �lm.It may be considered that the protective �lm formed may go into transpassive state, where the �lm is bro�en [43].

Analysis of Polarization Curves.
A polarization study has been used to detect the formation of protective �lm on the metal surface [44].When a protective �lm formed on the metal surface, the linear polarization resistance (LPR) increases, and the corrosion current ( corr ) decreases.e potentiodynamic polarization curves of carbon steel immersed in various test solution are shown in Figure 1.e corrosion parameters, namely, corrosion potential ( corr ) tafel slopes ( c = cathodic;  a = anodic), linear polarization resistance (LPR), and the corrosion current ( corr ) are given in

Analysis of Ac
Impedance Spectra.AC impedance spectra have been used to detect the formation of the �lm formed on the metal surface.If the protective �lm is formed, the charges transfer resistance increases, and double layer capacitance value decreases [40].e AC impedance spectra of carbon steel immersed in various solutions are shown in Figure 2 (Nyquist) and Figure 3 (impedance-Bode plots).e AC impedance parameter, namely, charge transfer resistance ( ct ) and double layer capacitance ( dl ) are given in Table 4.When carbon steel is immersed in aqueous solution containing seawater, the  ct value is 88 ohm cm 2 , and  dl value is 1.027 × 10 −7 F/cm 2 .When 4 ml of (Cuminum cyminum) extract is added, the  ct value increases from 88 ohm cm 2 to 116 ohm cm 2 , and  dl value decreases from 1.027 × 10 −7 F/cm 2 to 0.7817 × 10 −8 .is suggest that a protective �lm is formed on the metal surface of the metal.Further there is increase in impedance log (Z/ohm), value from 2.02 to 2.12 (derived from Bode plot shown in Figure 3).

Fourier
Transfer-Infrared Spectra.e main constituent of Jeera extract is cuminaldehyde [47].e structure of cuminaldehyde is shown in Scheme 1.It contain carboxylic group, cumin structure.
e Cuminum cyminum extract was evaporated to dryness to a solid mass.Its FTIR spectrum is shown in Figure 4(a).-C=C stretching frequency appeared at 2141 cm −1 .e aromatic -CH stretching frequency appeared at 2927 cm −1 .-C=O stretching frequency appeared at 1607 cm −1 [48,49].e F�IR spectrum of the protective �lm formed on the surface of the metal aer immersion in the aqueous solution containing seawater and Seawater containing 4 mL of Jeera extract is shown in Figure 4(b).-OH stretching frequency appeared at 3402 cm −1 to 3435 cm −1 .-C=C stretching frequency appeared at 2141 cm −1 to 2091 cm −1 .e aromatic -CH stretching frequency appeared at 2927 cm −1 to 2923 cm −1 .-C=O stretching frequency appeared at 1607 cm −1 to 1638 cm −1 .Fe 2+ sis added to the aqueous solution of Cuminum cyminum, peak appears at 225 nm and 265 mm [46].e �uorescence spectrum ( ex = 225 nm) of an aqueous solution of Fe 2+ -Cuminum cyminum is shown in Figure 6(a).A peak appears at 252 nm.is due to that Fe 2+ -active principle complex is formed in solution [40].

Fluorescence Spectra. e UV-visible adsorption spectrum of aqueous solution of Cuminum cyminum and Fe
e �uorescence spectrum ( ex = 225 nm) of the �lm formed on the surface of the metal aer immersion in the solution containing seawater and 4 ml of Cuminum cyminum extract is shown in Figure 6(b).e peaks appeared at 252 nm con�rming the presence of Fe 2+ -Cuminum cyminum extract complex formed on the metal surface.

Conclusion
e corrosion inhibition by aqueous solution of Jeera extract in the presence and absence of inhibitor was studied by weight-loss study and electrochemical measurements.e results show that inhibitor has the ability of reducing the corrosion rate of carbon steel in aqueous solution containing Jeera extract, and it acts as an anodic inhibitor.is effectiveness is con�rmed by electrochemical impedance spectra and potential polarization analysis.

F 7 :
2+ is shown in Figure5.Peaks appear at 228 nm, 268 nm.When the dl s ct Equivalent electrical circuit diagram. s : solution resistance;  ct : charge transfer resistance;  dl : double layer capacitance.
Table 2shows the values of corrosion rates and inhibition efficiencies obtained from weight loss measurements of different concentrations of Jeera extract.4 mL of the Jeera extract offered 93% corrosion inhibition efficiency to carbon steel immersed in 100 ml solution containing seawater.When the T 2: Corrosion rates (milligram per square decimeter per day) (Mdd) of carbon steel immersed in seawater in the presence and absence of inhibitors and the inhibition efficiencies (Ie) obtained by mass loss method.Inhibitor: Jeera extracts (Cuminum cyminum).

Table 3
when carbon steel is immersed in seawater.e corrosion potential of seawater is −926 mV VS SCE.e formulation consisting of 4 mL of Jeera extract in presence of seawater solution shis the corrosion potential −883 mV VS SCE.is suggested that anodic reaction is controlled predominantly.e (LPR) value increases from 51.67 × 10 −2 to 63.67 × 10 −2 ohm cm 2 .is suggests that a protective �lm is formed T 3: Corrosion parameters of carbon steel immersed in seawater in the absence and presence of inhibitors.System corr mV versus SCE  c mV/decade  a mV/decade LPR Ohm cm 2  corr A/cm 2