# Expired Chicken Egg-White Extract’s Adsorption Behavior As a Corrosion Inhibitor for Carbon Steel in 1M HCl

Authors: Esseddik Elqars; Mohamed Guennoun; Aicha Ouarhach; Noufissa Sqalli Houssini; Mohammed Elhafdi; Abdelhafid Essadki; Mohamed Ait chaoui; Taibi Nbigui
Journal: Journal of Chemistry
 (2021)

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## Abstract

The inhibitory activity of the expired egg-white carbon steel (CS) extract in HCl solution was studied in this article. The extract was examined using FT-IR, and the surface was examined using a scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDX). Weight loss techniques at various temperatures were used to examine corrosion investigations (298, 308, 318, and 328 K), concentrations (100, 200, 400, and 800 mg. L−1) of extracts, and electrochemical measurements (potentiodynamic polarization (PDP) and impedance spectroscopy (EIS) at 25°C and different concentrations. Results. Results obtained through EIS demonstrated a maximal inhibition efficiency of 90% at an inhibitor concentration of 800 mg. L−1. Moreover, the findings of the potentiodynamic polarization indicated that egg-white extract was a mixed type of inhibitor and slowed down both cathodic and anodic reactions. For weight loss analysis, an inhibitory potency (89, 83, 77, and 71%) at various temperatures (298, 308, 318, and 328 K) was demonstrated, respectively. It indicates that the temperature rise contributes to a decrease in the resistance of the carbon steel. The adsorption of the expired egg-white extract was spontaneous with physisorption and chemisorption according to the Langmuir isotherm model, according to adsorption isotherm studies.


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## Body

## 1. Introduction

The corrosion of carbon steel in acidic environments has become a fundamental and industrial problem because of the strong interest of scientists and engineers around the world [1]. The comprehensive use of structural and machinery building purposes renders carbon steel a metallic alloy vulnerable to corrosion degradation [2]. It is further exacerbated by its attractive mechanical and physical qualities, recyclability expense, and availability [3]. Mineral acid is often used in industry to chemically clean carbon steel, stainless steel, titanium, copper, and other alloys [4, 5]. Under these conditions, the choice of inhibitor or inhibitor formulation will depend on the corrosion system involved, especially the nature of the acid, the presence of dissolved organic or inorganic compounds, as well as the temperature, etc. [6, 7]. As corrosion inhibitors, the development of organic extracts has exceeded a certain level; currently, they are the first choice for inhibitors. The inhibitory action of these organic compounds is due to the development of a more or less continuous barrier that inhibits the solution for accessing the metal (or via adsorption) [8–10]. The organic compounds used as inhibitors must have at least one heteroatom working as an active center for their fixation on the metal such as nitrogen (amines, amides, imidazolines, and triazoles), oxygen (acetylenic alcohols, carboxylates, and oxadiazoles), sulfur (thiourea derivative, mercaptans, sulfoxides, and thiazoles), or phosphorus (phosphonates); one limitation in the application of these products may be the increase in temperature as organic molecules are often unstable at high temperatures [11–13]. Amino acids are effective and environment-friendly corrosion inhibitors that have been extensively researched in experiments and theory under various conditions. Almost all of these amino acids have been tested in acidic solutions against iron corrosion [14–16].Inhibitors have the originality of being the only means of intervention from the corrosive medium, which makes them an easy and inexpensive method of corrosion control, provided that the products used are of moderate cost [17–19]. In recent years, various studies have centered on reducing the harmful effects of human life on the earth and its potential to sustain life [20, 21]. Thus, there is increasing interest in biodegradable chemistry as there is a demand for innovative ecologically friendly products and biodegradable natural inhibitors from plant or animal origin with a lower concentration to provide greater efficacy [22, 23].Currently, many types of research are focussing on corrosion inhibition by organic extracts that give a good efficiency such as corrosion inhibition inSwertia chirata extract in an acid environment (0.5 M H2SO4) [24], Thevetia peruviana (Kaner) flower extract (TPFE) [25], leaf extract of Arbutus unedo L. [26], Crotalaria pallida leaf extracts [27], which were tested for mild steel, in 1M HCl. In our work, we have chosen the expired chicken egg, especially the white part, because the yellow part contains just lipids and the other contains of organic and mineral elements; for this reason, we have chosen the white part [28–31]. Expired egg white, which is available all over the world and is less expensive as an organic (animal origin) corrosion inhibitor for carbon steel in a 1M HCl solution, has a 90% effectiveness at 298 K; we examined weight loss (WL) and electrochemical tests such as potentiodynamic polarization (PDP) curves, electrochemical impedance spectroscopy (EIS), and SEM and EDX to assess the inhibitor efficacy. The isotherm and thermodynamic adsorption characteristics, as well as the adsorption mechanism, are all investigated.


## 2. Experimental Procedures

### 2.1. Extraction Procedure

Figure1 shows the preparation of expired egg-white extract (EEW). The EEW is dried in an oven at 308 K for 120 hours to make the drying completely uniform. Then, the resulting solid was crushed and sieved to obtain a fine powder. Accurate amounts were added to a concentrated 1M HCl solution (37%) to get the total solubility. Then, the whole solution was adjusted with distilled water to finally obtain extract concentrations (0.1, 0.2, 0.4, and 0.8 g/L) in a 1M HCl solution.Figure 1
Extraction flowchart of EEW.


### 2.2. Weight Loss Measurements

The inhibitory effect of the EEW extract was tested on a carbon steel specimen with dimensions of 2.26-1.33-0.30 cm2 and a chemical composition of 0.63 Cr (percent by weight) and S, 0.35–0.39% C, 0.50–0.80% Mn, Ni, and Mo, 0.015–0.035% S, 0.35–0.39% C, 0.50–0.80 Mn, and 0.40% Si, with the rest being Fe. We repeated each test three times for consistency, and the analytical balance can read up to four decimal places. The carbon steel specimen was polished with 400-, 600-, 800-, and 1200-grade abrasive paper before each experiment. Acetone was used to degrease the surface, which was then rinsed with distilled water. The samples were subsequently submerged in 100 ml of EEW extract at various concentrations. The examination lasted 6 hours. They were weighed again after being washed with distilled water. This investigation was also carried out at various temperatures (298, 308, 318, 328 K).The rate of corrosion (CR), (θ) surface coverage, and inhibition efficiency (η%) [32, 33] were put to use.(1)CR=W0−WtS.t,θ=CRint,0−CRinhCRint,0,η%=CRinh,0−CRinhCRinh,0×100,where W0 and Wt are, respectively, the carbon steel mass values before and after immersion in the corrosive solution (mg). S is the carbon steel surface area cm2, t is the corrosion time in (h), CRinh and CRint,0 are, respectively, the corrosion rate, with and without inhibitors g.cm2h−1.


### 2.3. Electrochemical Measurements

An OrigaLys potentiostat was used to make the electrochemical measurements. The Origa Master 5 software controls the system is fitted with a traditional three-electrode setup. The working electrode (WE) was made of carbon steel with a diameter of 0.28 cm2. The platinum electrode serves as a counter electrode (CE), while the reference electrode is a calomel-saturated (Hg2Cl2/Hg) electrode (RE). The electrode potential was automatically adjusted in the range of 300 mV more or less than the Ecorr at 1 mV/s to evaluate potentiodynamic polarization (PDP) curves. The frequency range for the measurements was 20 kHz to 200 MHz, with a 20 point per decade amplitude. Prior to each test, the working electrode (WE) was polished using abrasive series paper (400, 600, 800, and 1200), and distilled water and acetone were used to monitor the process. All of the trials were carried out at 298 K.


## 2.1. Extraction Procedure

Figure1 shows the preparation of expired egg-white extract (EEW). The EEW is dried in an oven at 308 K for 120 hours to make the drying completely uniform. Then, the resulting solid was crushed and sieved to obtain a fine powder. Accurate amounts were added to a concentrated 1M HCl solution (37%) to get the total solubility. Then, the whole solution was adjusted with distilled water to finally obtain extract concentrations (0.1, 0.2, 0.4, and 0.8 g/L) in a 1M HCl solution.Figure 1
Extraction flowchart of EEW.


## 2.2. Weight Loss Measurements

The inhibitory effect of the EEW extract was tested on a carbon steel specimen with dimensions of 2.26-1.33-0.30 cm2 and a chemical composition of 0.63 Cr (percent by weight) and S, 0.35–0.39% C, 0.50–0.80% Mn, Ni, and Mo, 0.015–0.035% S, 0.35–0.39% C, 0.50–0.80 Mn, and 0.40% Si, with the rest being Fe. We repeated each test three times for consistency, and the analytical balance can read up to four decimal places. The carbon steel specimen was polished with 400-, 600-, 800-, and 1200-grade abrasive paper before each experiment. Acetone was used to degrease the surface, which was then rinsed with distilled water. The samples were subsequently submerged in 100 ml of EEW extract at various concentrations. The examination lasted 6 hours. They were weighed again after being washed with distilled water. This investigation was also carried out at various temperatures (298, 308, 318, 328 K).The rate of corrosion (CR), (θ) surface coverage, and inhibition efficiency (η%) [32, 33] were put to use.(1)CR=W0−WtS.t,θ=CRint,0−CRinhCRint,0,η%=CRinh,0−CRinhCRinh,0×100,where W0 and Wt are, respectively, the carbon steel mass values before and after immersion in the corrosive solution (mg). S is the carbon steel surface area cm2, t is the corrosion time in (h), CRinh and CRint,0 are, respectively, the corrosion rate, with and without inhibitors g.cm2h−1.


## 2.3. Electrochemical Measurements

An OrigaLys potentiostat was used to make the electrochemical measurements. The Origa Master 5 software controls the system is fitted with a traditional three-electrode setup. The working electrode (WE) was made of carbon steel with a diameter of 0.28 cm2. The platinum electrode serves as a counter electrode (CE), while the reference electrode is a calomel-saturated (Hg2Cl2/Hg) electrode (RE). The electrode potential was automatically adjusted in the range of 300 mV more or less than the Ecorr at 1 mV/s to evaluate potentiodynamic polarization (PDP) curves. The frequency range for the measurements was 20 kHz to 200 MHz, with a 20 point per decade amplitude. Prior to each test, the working electrode (WE) was polished using abrasive series paper (400, 600, 800, and 1200), and distilled water and acetone were used to monitor the process. All of the trials were carried out at 298 K.


## 3. Results and Discussion

### 3.1. FT-IR Spectroscopy Results

The presence of functional groups and heteroatoms is the most crucial item in the adsorption of inhibitor molecules to the iron surface, as seen in the FT-IR spectrum of expired egg-white extract in Figure2. The existence of various functional groups may be seen in the IR spectra (Figure 2). The wide and strong bands in the range of 3500–3000 cm−1 are attributed to the OH/N–H/CH group [34]. The bands observed at 1650 cm−1 correspond to the C=O stretch group, and the absorption bands at 1550 cm−1 correspond to N–H/C=C stretch (aromatic nucleus) [35]. The C–H2 bands are observed around 1460 cm−1 and 1396 cm−1.The bands between 1360 and 1080 cm−1 are assigned to the C-N bands [36].Figure 2
The EEW aqueous extract’s infrared spectrum.


### 3.2. WL Measurements

To get a better understanding of how corrosion is inhibited. The weight loss technique was used to examine the effect of different doses on the inhibitory potential of EEW at 298, 308, 318, and 328 K. Table1 and Figure 3 demonstrate the corrosion rate (CR) and inhibition efficiency (η%); the efficacy of the inhibition rises as the inhibitor concentration increases, suggesting an increase in surface coverage and blocking the activation activity on the carbon steel surface. Furthermore, these findings revealed that, at all temperatures examined, the inhibition was efficient, the EEW lowered the CR values, and as the temperature of the solution grew, the percent values for EW dropped. This lowered corrosion rate with rising temperature may be explained further by a preexponential factor, which results from decreased desorption of inhibitor species from the carbon steel surface. The influence of temperature on the ΔHads and ΔSads of the corrosion process may be assessed.Table 1
Carbon steel corrosion weight loss results in a 1 M HCl solution in the absence and presence of different inhibitor concentrations and EEW temperatures from 298 to 328 K.
298 K308 K318 K328 KCinhg.l−1CRg.cm−2h−110−3θη%CRg.cm−2h−110−3θη%CRg.cm−2h−110−3θη%CRg.cm−2h−110−3θη%Blank3.344.295.096.310.10.990.71701.460.66662.130.58582.940.53530.20.750.78781.140.73731.670.67672.460.61610.40.590.82820.990.77771.480.71712.260.64640.80.380.89890.720.83831.220.76761.820.7171Figure 3
(a) Inhibition efficiency and (b) corrosion rate with the effect of temperature for different concentrations of the extract EEW.
(a)(b)


### 3.3. Adsorption Isotherm and Thermodynamic Parameters

Adsorption isotherm investigations reveal the process by which inhibitors bind to metal surfaces. Adjusting the corrosion rate CR and the degree of inhibitor surface coverage yielded the isotherm adsorption model that best reflects the adsorption of EEW on carbon steel in a 1 M HCl medium. Different isotherm adsorption models are used (Langmuir, Temkin, El-Awady’s, Freundlich, and Flory–Huggins) expressed in the linear form:Langmuir adsorption isotherm [37]:(2)Cinhθ=1Kads+Cinh.El-Awady’s thermodynamic/kinetic adsorption isotherm model [38, 39]:(3)logθ1−θ=y.logCinh+logK.Temkin adsorption isotherm model [40]:(4)θ=lnCR+Kads.Freundlich adsorption isotherm [41]:(5)logθ=logKads+n.logCinh.Flory–Huggins adsorption isotherm [42]:(6)logθCR=b.log1−θ+logKads.This research is to find the R2 correlation coefficient for each isothermal model of Table2. The best‐fitting model was chosen based on the correlation coefficient. In this research, the Langmuir isotherm with a 0.999 corrélation coefficient value provided the greatest match to experimental data. In a hydrochloric acid medium, it explains a superior adsorption mechanism of the EEW extract on carbon steel.To comprehend the kind of EEW adsorption in the metal/solution contact, the following formula is used to calculate the value of ΔGads:(7)ΔGads=−RT.lnCH2O.Kads,where T is the absolute temperature (K), R is the gas constant, Kads is the adsorption equilibrium constant calculated from the isotherm, 8.314JK−1mol−1, and CH2O is the value of the concentration of water in the solution 1000g.l−1[43, 44].The negative values ofΔGads obtained as in Table.3, according to Figure 4, guarantee the adsorption mechanism’s spontaneity and stability on the carbon steel surface. The ΔGads values are between −25 and −26kJ.mol−1, which are lower than −20kJ.mol−1 and higher than −40kJ.mol−1, indicating that adsorption of inhibitor molecules on the carbon steel surface includes both physisorption and chemisorption [45].Table 2
Correlation coefficient values for the various adsorption isotherms considered.
LangmuirEl-Awady’sTemkinFreundlichFlory–HugginsTemperature (k)R2R2R2R2R22980.99940.98690.97750.99030.97993080.99920.98550.98640.97830.97983180.99940.98350.99040.96170.98203280.99860.98000.99330.97120.9731Figure 4
Langmuir adsorption isotherm model for EEW on the carbon steel surface at temperatures from 298 to 328 K.The corrosion thermodynamic parameters were used to further analyze the adsorption behavior of EEW on the carbon steel surface. Arrhenius and transition state equations were used to calculate activation energy (Ea), entropy (ΔSa), and activation enthalpy (ΔHa).The activation energy (Ea) was calculated using the following equation [46]:(8)logCR=−Ea2.303RT+logλ,where R is the universal gas constant, T is the absolute temperature (K), and is the frequency factor.The connection between Log (CR) and1000/T in 1 M HCl without and with the EW inhibitor produces straight lines with slopes of Ea/2.303RT, as illustrated in Figure 5. The estimated values of the apparent activation energy using equation (8) are given in Table 4.The equation of transition states is(9)logCRT=−ΔHads2.303R1T+ΔSads2.303R+logRNA.h,where NA=6.023×1023 is Avogadro’s number, h=6.62607×10−34is Planck’s constant, ΔHads is the enthalpy, and ΔSadsis the entropy of adsorption. Figure 6 displays the plot of logCR/T versus which will give a straight line, with a slope of ΔHads/2.303R and an intercept ofΔSads/2.303R+logR/NA.h. Thus, giving the values of ΔSads and ΔHads, results are shown in Table 4.Table 3
Thermodynamic characteristics for 1 M HCl adsorption on carbon steel at temperatures of 298; 308; 318; and 328 K.
T(K)Kadsg.L−1ΔGkJ.mol−129824.58−25.0530822.84−25.7031818.55−25.9832815.26−26.27Figure 5
Carbon steel corrosion in 1 M HCl in the absence and presence of EW and the Arrhenius plot of log (CR) versus 1000/T. The activation entropy (ΔSads) and activation enthalpy (ΔHads) are shown, and Arrhenius was used to achieve the results [47].Table 4
Values forEa, ΔHads, and ΔSads in the absence of inhibitors and in the presence of inhibitors of varying doses.
Cinhg.L−1EakJ.mol−1ΔHadskJ.mol−1Ea−ΔHadsΔSadsJ.mol−1.K−1Blank16.9014.302.60−244.340.129.9527.352.60−210.690.232.2129.612.60−205.470.435.9333.332.60−194.810.842.3239.722.60−176.88Figure 6
Transition state plot of log (CR/T) vs. 1000/T for carbon steel corrosion in 1 M HCl in the absence and presence of EEW.The valuesΔHads are positive, indicating an endothermic corrosion process [48]. The values of Ea and ΔHadshave increased in the presence of an inhibitor EEW due to the increased energy barrier of the corrosion reaction occurring at the metal surface. Because the corrosion process is a unimolecular reaction, the mean value of the difference Ea−ΔHads is 2.60 kJ/mol, which is identical to the mean value of the product RT described by the following equation: Ea−ΔHads=RT[49].The activation entropy’s high and negative values indicate that the complex activated in the rate-determining step is an association rather than a dissociation phase, implying that there is a decrease in disorder throughout the transition from reactants to activated complexes [50].


### 3.4. Electrochemical Studies

#### 3.4.1. PDP Measurements

Carbon steel polarization curves in a 1M HCl solution at 298 K were also produced in the absence and presence of EEW inhibitors of various doses. The entire behavior of the steel/acid/inhibitor system is depicted in Figure7. Table 5 illustrates the inhibition efficacy of different doses of inhibitor in 1M HCl for corrosion current densities (Icorr), corrosion potential (Ecorr), Tafel slope (βa) and (βc), and EI (%). Equation (10) defines the corrosion inhibiting effectiveness (%):(10)ηPDP=icoor−iinhicoor×100.Figure 7
Carbon steel polarization curve in 1M HCl without and with the addition of EEW at 298 K.Table 5
Electrochemical parameters of impedance for carbon‐steel in 1M HCL, without and with EEW at 298 K.
Cinhmg.l−1RsΩ.cm2RpΩ.cm2nCdlμF/cm2ηEIS%Blank1.184327.970.996507.19—1001.692295.260.994132.72712002.7586128.130.989124.13784001.7158184.390.992108.65858001.9662271.770.99682.71890The current densities without and with inhibitor, as calculated by extrapolation of the Tafel lines, are Icorr and Iinh, respectively [51, 52].The inhibitory capacity of the inhibitor was studied using a polarization test, and the results are shown in Figure7; it can be seen that by the successive addition of an egg-white extract to the 1 M HCl medium, in the presence of the EEW, the corrosion potential is somewhat pushed towards the cathode branch, with a fluctuation in the values of βa and βc. This indicates that the presence of inhibitors in an acidic environment slowed both carbon steel dissolving and hydrogen reduction [53, 54]. In comparison to the blank, there is no significant change in the corrosive potential readings. The Ecorr is displacement is less than 85 mV, indicating that it is a mixed-character inhibitor [55, 56]. As the corrosion concentration of the inhibitors increases, the corrosion current density values decrease [57] according to the data given in Table 6. These results can be ascribed to the adsorption of EEW on the carbon steel surface, which reduces the active site’s surface area and can function as a corrosion barrier [58, 59]. It should also be noted that a good inhibition efficiency was observed in the presence of EEW (89%) at a concentration of 800 mg. L−1.Table 6
Potentiodynamic polarization results for carbon‐steel in 1M HCL, without and with EEW at 298 K.
Cinhg.l−1−Ecoormv/SCEicoorμA/cm2βamv/d´ec−βcmv/d´ecηPDP%Blank461.8735.5121.0129.5—100424.4210.989.0148.371200436.4174.498.0114.376400447.5135.2106.3122.482800445.280.485.3106.489


#### 3.4.2. Impedance Spectroscopy Electrochemical

Electrochemical impedance spectroscopy is widely and effectively applied in global corrosion and protection processes, addressing the use of electrochemical impedance measurements to investigate the inhibitory mechanism; it seems that this technique is particularly adapted to determine the mode of action of inhibitors; it allows evaluating the dielectric characteristics of the film formed and to follow their evolution according to many parameters [60, 61]. It also makes it possible to explain the chemical or electrochemical processes developing through the films. In this study of corrosion inhibition of carbon steel in 1 M HCL acid media at 298 K, the impedance of the Nyquist and Bode diagrams is presented in Figures 8(a)and 8(b).Figure 8
(a) Nyquist plots in the absence and presence of a different concentration of EEW, equivalent circuit used, and (b) bode-phase angle plots in the absence and presence of a different concentration of EEW.
(a)(b)Figure8(a) shows the equivalent circuit, rather than using capacitors, uses stationary-phase elements (CPE) to provide a variety of heterogeneities suitable for corrosion electrodes, such as deficient polishing, grain boundary, surface contaminants, and surface roughness [62]. We utilized the parameters (n and Y0) of our test to construct a mathematical model since the impedance of carbon steel is frequency dependent.(11)ZCPE=1Y0jwn,where Y0 denotes the CPE constant, j is an imaginary number and j2 = −1, ω represents the angular frequency in rad−1 and ω = 2πf, and n is a measure of the roughness of the carbon steel surface; 0 ≤ n ≤ 1 [63]. In addition, this is due to a variety of factors, including electrode roughness, dielectric constant, and surface heterogeneity; in our research, the n values are in a range of 0.981 < n < 0.996, indicating that inhibitors have no effect on the mechanism of corrosion and that the electron transfer reaction regulates the corrosion process both in the absence and presence of inhibitors [64]. The following equation was used to determine the double-layer amplitude (Cdl):(12)Cdl=12πfmaxRp,where fmax is the maximum frequency of the imaginary component of the impedance and Rp is the charge transfer resistance; it is evident from Table 5 that the Cdl values decreased in the presence of the inhibitor, owing to an increase in the thickness of the protective layer on the electrode surface in the presence of an inhibitor [65]; in other words, the decrease in Cdl values is attributed to the progressive replacement of water molecules adsorbed on the metal surface by larger water molecules [66].In this work, we looked at the efficacy of inhibitionηEIS% using the following equation [67]:(13)ηEIS=Rs−RpR2×100,where Rpinh and Rpcorrare the charge transfer resistance values with and without EEG, respectively; furthermore, it is clear from Table 5 that the values of Rp increase significantly with the increase of the inhibitor concentration in the acid solution, the polarization resistance (Rp) is inversely related to the corrosion rate, and the creation of an insulating protective coating at the metal/solution contact is responsible for the increase in Rp values [68]. This gives a maximum inhibitor concentration efficiency of 90% at 800 mg/L of EEW; these findings support the hypothesis that EEW works via adsorption at the metal/solution contact. Figure 8(b) show the impedance data in Bode diagrams of impedance size (|Z |) and full-frequency angle of phase for the C-steel electrode obtained at various inhibitor doses; furthermore, when the concentration of inhibitors increases, the angle of phase increases up to 65° in comparison to the noninhibited system, indicating an improvement in inhibition performance via EEG adsorption on the CS surface [69, 70]. This may explain the efficacy in the current research due to the presence of these features in the EEG, as well as delocalized electron density in the majority of the molecular structure. In the same way, the higher efficiency of EEG, in contrast to Lilium brownii leaf extract [71], camphor leaf extract [72], and Tamarindus indica extract [73], can be explained by that the EEG contains many electron sources such as oxygen atoms, nitrogen atom, and hydroxy group, confirming the benefit of using EEG as a corrosion inhibitor.


#### 3.4.3. EDX Spectra and Scanning Electron Microscopy (SEM) Surface Analysis

Figure9 shows the surface morphology of carbon steel during 12 hours of immersion with and without an inhibitor in a 1M HCl solution at 298 K. The SEM analysis shows the surface of the steel with and without an inhibitor so that the surface with an inhibitor is at the energy 20 KV. The surface morphology was severely degraded by exposing the specimen to 1 M HCl, as seen in Figure 9 (blank). After immersion in an acidic solution containing 800 mg, the surface of the specimen was smoother and revealed fewer pits. When inhibitor molecules engage with the corroding surface of CS in the acid solution, a protective barrier layer is formed, resulting in the smoothness of the inhibited CS surface [74–76].Figure 9
SEM image of the surface with an inhibitor and without an inhibitor (EW) of carbon steel with EDX spectra corresponding to each image.


## 3.1. FT-IR Spectroscopy Results

The presence of functional groups and heteroatoms is the most crucial item in the adsorption of inhibitor molecules to the iron surface, as seen in the FT-IR spectrum of expired egg-white extract in Figure2. The existence of various functional groups may be seen in the IR spectra (Figure 2). The wide and strong bands in the range of 3500–3000 cm−1 are attributed to the OH/N–H/CH group [34]. The bands observed at 1650 cm−1 correspond to the C=O stretch group, and the absorption bands at 1550 cm−1 correspond to N–H/C=C stretch (aromatic nucleus) [35]. The C–H2 bands are observed around 1460 cm−1 and 1396 cm−1.The bands between 1360 and 1080 cm−1 are assigned to the C-N bands [36].Figure 2
The EEW aqueous extract’s infrared spectrum.


## 3.2. WL Measurements

To get a better understanding of how corrosion is inhibited. The weight loss technique was used to examine the effect of different doses on the inhibitory potential of EEW at 298, 308, 318, and 328 K. Table1 and Figure 3 demonstrate the corrosion rate (CR) and inhibition efficiency (η%); the efficacy of the inhibition rises as the inhibitor concentration increases, suggesting an increase in surface coverage and blocking the activation activity on the carbon steel surface. Furthermore, these findings revealed that, at all temperatures examined, the inhibition was efficient, the EEW lowered the CR values, and as the temperature of the solution grew, the percent values for EW dropped. This lowered corrosion rate with rising temperature may be explained further by a preexponential factor, which results from decreased desorption of inhibitor species from the carbon steel surface. The influence of temperature on the ΔHads and ΔSads of the corrosion process may be assessed.Table 1
Carbon steel corrosion weight loss results in a 1 M HCl solution in the absence and presence of different inhibitor concentrations and EEW temperatures from 298 to 328 K.
298 K308 K318 K328 KCinhg.l−1CRg.cm−2h−110−3θη%CRg.cm−2h−110−3θη%CRg.cm−2h−110−3θη%CRg.cm−2h−110−3θη%Blank3.344.295.096.310.10.990.71701.460.66662.130.58582.940.53530.20.750.78781.140.73731.670.67672.460.61610.40.590.82820.990.77771.480.71712.260.64640.80.380.89890.720.83831.220.76761.820.7171Figure 3
(a) Inhibition efficiency and (b) corrosion rate with the effect of temperature for different concentrations of the extract EEW.
(a)(b)


## 3.3. Adsorption Isotherm and Thermodynamic Parameters

Adsorption isotherm investigations reveal the process by which inhibitors bind to metal surfaces. Adjusting the corrosion rate CR and the degree of inhibitor surface coverage yielded the isotherm adsorption model that best reflects the adsorption of EEW on carbon steel in a 1 M HCl medium. Different isotherm adsorption models are used (Langmuir, Temkin, El-Awady’s, Freundlich, and Flory–Huggins) expressed in the linear form:Langmuir adsorption isotherm [37]:(2)Cinhθ=1Kads+Cinh.El-Awady’s thermodynamic/kinetic adsorption isotherm model [38, 39]:(3)logθ1−θ=y.logCinh+logK.Temkin adsorption isotherm model [40]:(4)θ=lnCR+Kads.Freundlich adsorption isotherm [41]:(5)logθ=logKads+n.logCinh.Flory–Huggins adsorption isotherm [42]:(6)logθCR=b.log1−θ+logKads.This research is to find the R2 correlation coefficient for each isothermal model of Table2. The best‐fitting model was chosen based on the correlation coefficient. In this research, the Langmuir isotherm with a 0.999 corrélation coefficient value provided the greatest match to experimental data. In a hydrochloric acid medium, it explains a superior adsorption mechanism of the EEW extract on carbon steel.To comprehend the kind of EEW adsorption in the metal/solution contact, the following formula is used to calculate the value of ΔGads:(7)ΔGads=−RT.lnCH2O.Kads,where T is the absolute temperature (K), R is the gas constant, Kads is the adsorption equilibrium constant calculated from the isotherm, 8.314JK−1mol−1, and CH2O is the value of the concentration of water in the solution 1000g.l−1[43, 44].The negative values ofΔGads obtained as in Table.3, according to Figure 4, guarantee the adsorption mechanism’s spontaneity and stability on the carbon steel surface. The ΔGads values are between −25 and −26kJ.mol−1, which are lower than −20kJ.mol−1 and higher than −40kJ.mol−1, indicating that adsorption of inhibitor molecules on the carbon steel surface includes both physisorption and chemisorption [45].Table 2
Correlation coefficient values for the various adsorption isotherms considered.
LangmuirEl-Awady’sTemkinFreundlichFlory–HugginsTemperature (k)R2R2R2R2R22980.99940.98690.97750.99030.97993080.99920.98550.98640.97830.97983180.99940.98350.99040.96170.98203280.99860.98000.99330.97120.9731Figure 4
Langmuir adsorption isotherm model for EEW on the carbon steel surface at temperatures from 298 to 328 K.The corrosion thermodynamic parameters were used to further analyze the adsorption behavior of EEW on the carbon steel surface. Arrhenius and transition state equations were used to calculate activation energy (Ea), entropy (ΔSa), and activation enthalpy (ΔHa).The activation energy (Ea) was calculated using the following equation [46]:(8)logCR=−Ea2.303RT+logλ,where R is the universal gas constant, T is the absolute temperature (K), and is the frequency factor.The connection between Log (CR) and1000/T in 1 M HCl without and with the EW inhibitor produces straight lines with slopes of Ea/2.303RT, as illustrated in Figure 5. The estimated values of the apparent activation energy using equation (8) are given in Table 4.The equation of transition states is(9)logCRT=−ΔHads2.303R1T+ΔSads2.303R+logRNA.h,where NA=6.023×1023 is Avogadro’s number, h=6.62607×10−34is Planck’s constant, ΔHads is the enthalpy, and ΔSadsis the entropy of adsorption. Figure 6 displays the plot of logCR/T versus which will give a straight line, with a slope of ΔHads/2.303R and an intercept ofΔSads/2.303R+logR/NA.h. Thus, giving the values of ΔSads and ΔHads, results are shown in Table 4.Table 3
Thermodynamic characteristics for 1 M HCl adsorption on carbon steel at temperatures of 298; 308; 318; and 328 K.
T(K)Kadsg.L−1ΔGkJ.mol−129824.58−25.0530822.84−25.7031818.55−25.9832815.26−26.27Figure 5
Carbon steel corrosion in 1 M HCl in the absence and presence of EW and the Arrhenius plot of log (CR) versus 1000/T. The activation entropy (ΔSads) and activation enthalpy (ΔHads) are shown, and Arrhenius was used to achieve the results [47].Table 4
Values forEa, ΔHads, and ΔSads in the absence of inhibitors and in the presence of inhibitors of varying doses.
Cinhg.L−1EakJ.mol−1ΔHadskJ.mol−1Ea−ΔHadsΔSadsJ.mol−1.K−1Blank16.9014.302.60−244.340.129.9527.352.60−210.690.232.2129.612.60−205.470.435.9333.332.60−194.810.842.3239.722.60−176.88Figure 6
Transition state plot of log (CR/T) vs. 1000/T for carbon steel corrosion in 1 M HCl in the absence and presence of EEW.The valuesΔHads are positive, indicating an endothermic corrosion process [48]. The values of Ea and ΔHadshave increased in the presence of an inhibitor EEW due to the increased energy barrier of the corrosion reaction occurring at the metal surface. Because the corrosion process is a unimolecular reaction, the mean value of the difference Ea−ΔHads is 2.60 kJ/mol, which is identical to the mean value of the product RT described by the following equation: Ea−ΔHads=RT[49].The activation entropy’s high and negative values indicate that the complex activated in the rate-determining step is an association rather than a dissociation phase, implying that there is a decrease in disorder throughout the transition from reactants to activated complexes [50].


## 3.4. Electrochemical Studies

### 3.4.1. PDP Measurements

Carbon steel polarization curves in a 1M HCl solution at 298 K were also produced in the absence and presence of EEW inhibitors of various doses. The entire behavior of the steel/acid/inhibitor system is depicted in Figure7. Table 5 illustrates the inhibition efficacy of different doses of inhibitor in 1M HCl for corrosion current densities (Icorr), corrosion potential (Ecorr), Tafel slope (βa) and (βc), and EI (%). Equation (10) defines the corrosion inhibiting effectiveness (%):(10)ηPDP=icoor−iinhicoor×100.Figure 7
Carbon steel polarization curve in 1M HCl without and with the addition of EEW at 298 K.Table 5
Electrochemical parameters of impedance for carbon‐steel in 1M HCL, without and with EEW at 298 K.
Cinhmg.l−1RsΩ.cm2RpΩ.cm2nCdlμF/cm2ηEIS%Blank1.184327.970.996507.19—1001.692295.260.994132.72712002.7586128.130.989124.13784001.7158184.390.992108.65858001.9662271.770.99682.71890The current densities without and with inhibitor, as calculated by extrapolation of the Tafel lines, are Icorr and Iinh, respectively [51, 52].The inhibitory capacity of the inhibitor was studied using a polarization test, and the results are shown in Figure7; it can be seen that by the successive addition of an egg-white extract to the 1 M HCl medium, in the presence of the EEW, the corrosion potential is somewhat pushed towards the cathode branch, with a fluctuation in the values of βa and βc. This indicates that the presence of inhibitors in an acidic environment slowed both carbon steel dissolving and hydrogen reduction [53, 54]. In comparison to the blank, there is no significant change in the corrosive potential readings. The Ecorr is displacement is less than 85 mV, indicating that it is a mixed-character inhibitor [55, 56]. As the corrosion concentration of the inhibitors increases, the corrosion current density values decrease [57] according to the data given in Table 6. These results can be ascribed to the adsorption of EEW on the carbon steel surface, which reduces the active site’s surface area and can function as a corrosion barrier [58, 59]. It should also be noted that a good inhibition efficiency was observed in the presence of EEW (89%) at a concentration of 800 mg. L−1.Table 6
Potentiodynamic polarization results for carbon‐steel in 1M HCL, without and with EEW at 298 K.
Cinhg.l−1−Ecoormv/SCEicoorμA/cm2βamv/d´ec−βcmv/d´ecηPDP%Blank461.8735.5121.0129.5—100424.4210.989.0148.371200436.4174.498.0114.376400447.5135.2106.3122.482800445.280.485.3106.489


### 3.4.2. Impedance Spectroscopy Electrochemical

Electrochemical impedance spectroscopy is widely and effectively applied in global corrosion and protection processes, addressing the use of electrochemical impedance measurements to investigate the inhibitory mechanism; it seems that this technique is particularly adapted to determine the mode of action of inhibitors; it allows evaluating the dielectric characteristics of the film formed and to follow their evolution according to many parameters [60, 61]. It also makes it possible to explain the chemical or electrochemical processes developing through the films. In this study of corrosion inhibition of carbon steel in 1 M HCL acid media at 298 K, the impedance of the Nyquist and Bode diagrams is presented in Figures 8(a)and 8(b).Figure 8
(a) Nyquist plots in the absence and presence of a different concentration of EEW, equivalent circuit used, and (b) bode-phase angle plots in the absence and presence of a different concentration of EEW.
(a)(b)Figure8(a) shows the equivalent circuit, rather than using capacitors, uses stationary-phase elements (CPE) to provide a variety of heterogeneities suitable for corrosion electrodes, such as deficient polishing, grain boundary, surface contaminants, and surface roughness [62]. We utilized the parameters (n and Y0) of our test to construct a mathematical model since the impedance of carbon steel is frequency dependent.(11)ZCPE=1Y0jwn,where Y0 denotes the CPE constant, j is an imaginary number and j2 = −1, ω represents the angular frequency in rad−1 and ω = 2πf, and n is a measure of the roughness of the carbon steel surface; 0 ≤ n ≤ 1 [63]. In addition, this is due to a variety of factors, including electrode roughness, dielectric constant, and surface heterogeneity; in our research, the n values are in a range of 0.981 < n < 0.996, indicating that inhibitors have no effect on the mechanism of corrosion and that the electron transfer reaction regulates the corrosion process both in the absence and presence of inhibitors [64]. The following equation was used to determine the double-layer amplitude (Cdl):(12)Cdl=12πfmaxRp,where fmax is the maximum frequency of the imaginary component of the impedance and Rp is the charge transfer resistance; it is evident from Table 5 that the Cdl values decreased in the presence of the inhibitor, owing to an increase in the thickness of the protective layer on the electrode surface in the presence of an inhibitor [65]; in other words, the decrease in Cdl values is attributed to the progressive replacement of water molecules adsorbed on the metal surface by larger water molecules [66].In this work, we looked at the efficacy of inhibitionηEIS% using the following equation [67]:(13)ηEIS=Rs−RpR2×100,where Rpinh and Rpcorrare the charge transfer resistance values with and without EEG, respectively; furthermore, it is clear from Table 5 that the values of Rp increase significantly with the increase of the inhibitor concentration in the acid solution, the polarization resistance (Rp) is inversely related to the corrosion rate, and the creation of an insulating protective coating at the metal/solution contact is responsible for the increase in Rp values [68]. This gives a maximum inhibitor concentration efficiency of 90% at 800 mg/L of EEW; these findings support the hypothesis that EEW works via adsorption at the metal/solution contact. Figure 8(b) show the impedance data in Bode diagrams of impedance size (|Z |) and full-frequency angle of phase for the C-steel electrode obtained at various inhibitor doses; furthermore, when the concentration of inhibitors increases, the angle of phase increases up to 65° in comparison to the noninhibited system, indicating an improvement in inhibition performance via EEG adsorption on the CS surface [69, 70]. This may explain the efficacy in the current research due to the presence of these features in the EEG, as well as delocalized electron density in the majority of the molecular structure. In the same way, the higher efficiency of EEG, in contrast to Lilium brownii leaf extract [71], camphor leaf extract [72], and Tamarindus indica extract [73], can be explained by that the EEG contains many electron sources such as oxygen atoms, nitrogen atom, and hydroxy group, confirming the benefit of using EEG as a corrosion inhibitor.


### 3.4.3. EDX Spectra and Scanning Electron Microscopy (SEM) Surface Analysis

Figure9 shows the surface morphology of carbon steel during 12 hours of immersion with and without an inhibitor in a 1M HCl solution at 298 K. The SEM analysis shows the surface of the steel with and without an inhibitor so that the surface with an inhibitor is at the energy 20 KV. The surface morphology was severely degraded by exposing the specimen to 1 M HCl, as seen in Figure 9 (blank). After immersion in an acidic solution containing 800 mg, the surface of the specimen was smoother and revealed fewer pits. When inhibitor molecules engage with the corroding surface of CS in the acid solution, a protective barrier layer is formed, resulting in the smoothness of the inhibited CS surface [74–76].Figure 9
SEM image of the surface with an inhibitor and without an inhibitor (EW) of carbon steel with EDX spectra corresponding to each image.


## 3.4.1. PDP Measurements

Carbon steel polarization curves in a 1M HCl solution at 298 K were also produced in the absence and presence of EEW inhibitors of various doses. The entire behavior of the steel/acid/inhibitor system is depicted in Figure7. Table 5 illustrates the inhibition efficacy of different doses of inhibitor in 1M HCl for corrosion current densities (Icorr), corrosion potential (Ecorr), Tafel slope (βa) and (βc), and EI (%). Equation (10) defines the corrosion inhibiting effectiveness (%):(10)ηPDP=icoor−iinhicoor×100.Figure 7
Carbon steel polarization curve in 1M HCl without and with the addition of EEW at 298 K.Table 5
Electrochemical parameters of impedance for carbon‐steel in 1M HCL, without and with EEW at 298 K.
Cinhmg.l−1RsΩ.cm2RpΩ.cm2nCdlμF/cm2ηEIS%Blank1.184327.970.996507.19—1001.692295.260.994132.72712002.7586128.130.989124.13784001.7158184.390.992108.65858001.9662271.770.99682.71890The current densities without and with inhibitor, as calculated by extrapolation of the Tafel lines, are Icorr and Iinh, respectively [51, 52].The inhibitory capacity of the inhibitor was studied using a polarization test, and the results are shown in Figure7; it can be seen that by the successive addition of an egg-white extract to the 1 M HCl medium, in the presence of the EEW, the corrosion potential is somewhat pushed towards the cathode branch, with a fluctuation in the values of βa and βc. This indicates that the presence of inhibitors in an acidic environment slowed both carbon steel dissolving and hydrogen reduction [53, 54]. In comparison to the blank, there is no significant change in the corrosive potential readings. The Ecorr is displacement is less than 85 mV, indicating that it is a mixed-character inhibitor [55, 56]. As the corrosion concentration of the inhibitors increases, the corrosion current density values decrease [57] according to the data given in Table 6. These results can be ascribed to the adsorption of EEW on the carbon steel surface, which reduces the active site’s surface area and can function as a corrosion barrier [58, 59]. It should also be noted that a good inhibition efficiency was observed in the presence of EEW (89%) at a concentration of 800 mg. L−1.Table 6
Potentiodynamic polarization results for carbon‐steel in 1M HCL, without and with EEW at 298 K.
Cinhg.l−1−Ecoormv/SCEicoorμA/cm2βamv/d´ec−βcmv/d´ecηPDP%Blank461.8735.5121.0129.5—100424.4210.989.0148.371200436.4174.498.0114.376400447.5135.2106.3122.482800445.280.485.3106.489


## 3.4.2. Impedance Spectroscopy Electrochemical

Electrochemical impedance spectroscopy is widely and effectively applied in global corrosion and protection processes, addressing the use of electrochemical impedance measurements to investigate the inhibitory mechanism; it seems that this technique is particularly adapted to determine the mode of action of inhibitors; it allows evaluating the dielectric characteristics of the film formed and to follow their evolution according to many parameters [60, 61]. It also makes it possible to explain the chemical or electrochemical processes developing through the films. In this study of corrosion inhibition of carbon steel in 1 M HCL acid media at 298 K, the impedance of the Nyquist and Bode diagrams is presented in Figures 8(a)and 8(b).Figure 8
(a) Nyquist plots in the absence and presence of a different concentration of EEW, equivalent circuit used, and (b) bode-phase angle plots in the absence and presence of a different concentration of EEW.
(a)(b)Figure8(a) shows the equivalent circuit, rather than using capacitors, uses stationary-phase elements (CPE) to provide a variety of heterogeneities suitable for corrosion electrodes, such as deficient polishing, grain boundary, surface contaminants, and surface roughness [62]. We utilized the parameters (n and Y0) of our test to construct a mathematical model since the impedance of carbon steel is frequency dependent.(11)ZCPE=1Y0jwn,where Y0 denotes the CPE constant, j is an imaginary number and j2 = −1, ω represents the angular frequency in rad−1 and ω = 2πf, and n is a measure of the roughness of the carbon steel surface; 0 ≤ n ≤ 1 [63]. In addition, this is due to a variety of factors, including electrode roughness, dielectric constant, and surface heterogeneity; in our research, the n values are in a range of 0.981 < n < 0.996, indicating that inhibitors have no effect on the mechanism of corrosion and that the electron transfer reaction regulates the corrosion process both in the absence and presence of inhibitors [64]. The following equation was used to determine the double-layer amplitude (Cdl):(12)Cdl=12πfmaxRp,where fmax is the maximum frequency of the imaginary component of the impedance and Rp is the charge transfer resistance; it is evident from Table 5 that the Cdl values decreased in the presence of the inhibitor, owing to an increase in the thickness of the protective layer on the electrode surface in the presence of an inhibitor [65]; in other words, the decrease in Cdl values is attributed to the progressive replacement of water molecules adsorbed on the metal surface by larger water molecules [66].In this work, we looked at the efficacy of inhibitionηEIS% using the following equation [67]:(13)ηEIS=Rs−RpR2×100,where Rpinh and Rpcorrare the charge transfer resistance values with and without EEG, respectively; furthermore, it is clear from Table 5 that the values of Rp increase significantly with the increase of the inhibitor concentration in the acid solution, the polarization resistance (Rp) is inversely related to the corrosion rate, and the creation of an insulating protective coating at the metal/solution contact is responsible for the increase in Rp values [68]. This gives a maximum inhibitor concentration efficiency of 90% at 800 mg/L of EEW; these findings support the hypothesis that EEW works via adsorption at the metal/solution contact. Figure 8(b) show the impedance data in Bode diagrams of impedance size (|Z |) and full-frequency angle of phase for the C-steel electrode obtained at various inhibitor doses; furthermore, when the concentration of inhibitors increases, the angle of phase increases up to 65° in comparison to the noninhibited system, indicating an improvement in inhibition performance via EEG adsorption on the CS surface [69, 70]. This may explain the efficacy in the current research due to the presence of these features in the EEG, as well as delocalized electron density in the majority of the molecular structure. In the same way, the higher efficiency of EEG, in contrast to Lilium brownii leaf extract [71], camphor leaf extract [72], and Tamarindus indica extract [73], can be explained by that the EEG contains many electron sources such as oxygen atoms, nitrogen atom, and hydroxy group, confirming the benefit of using EEG as a corrosion inhibitor.


## 3.4.3. EDX Spectra and Scanning Electron Microscopy (SEM) Surface Analysis

Figure9 shows the surface morphology of carbon steel during 12 hours of immersion with and without an inhibitor in a 1M HCl solution at 298 K. The SEM analysis shows the surface of the steel with and without an inhibitor so that the surface with an inhibitor is at the energy 20 KV. The surface morphology was severely degraded by exposing the specimen to 1 M HCl, as seen in Figure 9 (blank). After immersion in an acidic solution containing 800 mg, the surface of the specimen was smoother and revealed fewer pits. When inhibitor molecules engage with the corroding surface of CS in the acid solution, a protective barrier layer is formed, resulting in the smoothness of the inhibited CS surface [74–76].Figure 9
SEM image of the surface with an inhibitor and without an inhibitor (EW) of carbon steel with EDX spectra corresponding to each image.


## 4. Conclusions

The inhibition behavior of the expired egg-white extract (EEW) in 1M HCl was examined using weight loss, electrochemical study, and SEM with EDX:Potentiodynamic polarization (PDP) studies show that this natural product is a mixed-type inhibitor and acts as an adsorptive inhibitorIncreasing the inhibitor concentration up to 800 mg/L at 298 K, the inhibition efficiency increases to 89% for (PDP) and 90% for (EIS)The site electrochemical impedance spectroscopy indicated that the ECP, with increasing inhibitor concentrations, and the charge transfer resistance of the electrical double layer dropped and the charge transfer resistance roseThe effect of temperature showed that extract adsorption occurs by physical and chemical adsorption and follows the Langmuir isothermScanning electron microscopy reveals the development of a protective layer on the metal surface



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*Source: 3416092-2021-09-10.xml*