A Study of the corrosion inhibition of aluminum in ethanol-gasoline blend by using Annona muricata leaves extract

doi:10.21203/rs.3.rs-4350296/v1

Download PDF

Research Article

A Study of the corrosion inhibition of aluminum in ethanol-gasoline blend by using Annona muricata leaves extract

https://doi.org/10.21203/rs.3.rs-4350296/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

The effect of Annona muricata leaves extract as an inhibitor of green corrosion of aluminum was investigated 20% cane ethanol and 80% gasoline blend solution for 91 days of immersion. It was evaluated using gravimetric and electrochemical techniques such as electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and electrochemical noise (EN). The studies revealed that Annona muricata extract is an efficient corrosion inhibitor, reaching its highest efficiency at concentrations of 20 and 25 ppm. This decrease in the corrosion rate is because the inhibitor adsorbs to the aluminum surface by physisorption according to the Langmuir adsorption isotherm and demonstrated a more notable protective effect Fourier transform infrared spectroscopy (FTIR) and gas chromatography coupled with mass spectrometry (GC-MS) analyzes were performed, which showed the presence of phenolic compounds, lauric acid, palmitic acid, linoleic acid, vitamin E and other compounds with antioxidant properties. The morphology of the aluminum surface was examined by scanning electron microscopy (SEM), showing the existence of a protective layer of Annona muricata extract that reduces pitting corrosion susceptibility of aluminum.

Bioethanol

Biofuels

Corrosion

Green inhibitors

The increase in environmental pollution, caused by the release of greenhouse gases, such as carbon dioxide (CO₂), methane (CH₄) and nitrogen dioxide (NO₂), which contribute to global warming, causing the melting of polar caps and glaciers, the acidification of the oceans, affect terrestrial ecosystems and human health. These adverse effects have generated a constant search for effective solutions to reduce the use of fossil fuels, which are the main source of CO₂ today [1, 2]. Biofuels such as biodiesel and bioethanol have been highlighted as a renewable energy alternative to replace fossil fuels fully or partially. Biodiesel is a mixture of alkyl esters produced by the transesterification of fatty acids from vegetable oils such as palm oil, soybean, sunflower, canola, palmitic, rapeseed, oleic, among others. It has also been made with used cooking oil and animal fats as byproducts of the agri-food industry [3, 4]. Bioethanol is produced by fermentation of biomass containing high starch or sugar content, such as corn, wheat, sugar cane, sugar beet and non-edible biomass such as lignocellulosic residues and agricultural forest residues (wood) [5, 6]. The main advantages of using biofuels are that they are biodegradable, reduce greenhouse gas emissions, produce fewer local pollutants, such as sulfur oxides (SO_X) and fine particles, compared to fossil fuels [7, 3]. This can contribute to improve the air quality in urban areas and reduce health problems related to air pollution. Biodiesel is completely miscible with petroleum diesel, which means that it can be used both in its pure form and in blends with conventional diesel. These blends are identified by the notation "BXX," where "XX" represents the percentage of biodiesel in the blend. For example, B100 refers to pure biodiesel, while a blend called B80 contains 80% biodiesel and 20% petroleum diesel [8]. While ethanol is used as an additive in gasoline to increase the octane number, which increases engine performance and reduces polluting emissions. The most common mixture is E10, which contains 10% ethanol and 90% gasoline [9]. More concentrated mixtures are also used, such as E85 (85% ethanol). However, some authors point out that ethanol when produced from raw materials such as corn or sugar cane can have more evident corrosive effects when its concentration increases to 20% or more. Kumar et al. carried out an evaluation of a piston composed of aluminum alloy and a carbon steel valve, exposing them to ethanol-gasoline fuel blend at different concentrations: E0, E20, E50 and E100, at room temperature. The results revealed that the corrosion rate was in the order of E100 < E50 < E20 < E0 during a period of 4320 hours [10]. Baena et al. evaluated the corrosion susceptibility of stainless steel, tin, carbon steel and copper in ethanol-gasoline fuel blend with concentrations of E30, E50, E85 and E100 at 45 ºC. Based on these results, it was observed that carbon steel presented a greater susceptibility to corrosion, showing a notable increase in the corrosion rate when exposed to concentrations of E100. On the other hand, it was observed that both stainless steel and tin exhibited a lower susceptibility to corrosion. However, an increase in the corrosion rate was observed in the following order: E100 < E85 < E50 < E30 [11].

Biofuels have a wide application globally, especially in the transportation sector, where they are mainly used in vehicles. However, they have some disadvantages such as lower caloric value and lower energy, miscibility with water reduces oxidative stability, which can result in corrosion problems and proliferation of microorganisms. Bioethanol, due to its ability to absorb water can form acetic acid, which leads to a reduction in the pH of the fuel and therefore causes a corrosive and degradative effect on the internal components of the engine. This affects both metallic materials, such as steel, zinc, aluminum and its alloys, copper and its alloys, as well as non-metallic materials, such as rubber and polymer components. Additionally, high temperature conditions within the engine can accelerate the corrosion process in these materials, which in turn can cause engine performance problems and failure [11–13]. To address this problem, the use of corrosion inhibitors in ethanol-gasoline systems has been widely investigated. Inhibitors composed of amines such as diethylenetriamine [14–16] or from plant leaves (Vitex negundo, Catharanthus roseu, Aegle marmelos, Elaeocarpus ganitrus [17], Aganonerion polymorphum [18] are effective.

Soursop (Annona muricata) is an evergreen plant native to the tropical areas of Central and South America, Africa, and Southeast Asia. The bark, fruits, seeds, and leaves have been used in a wide variety of diseases due to their anti-inflammatory, antibacterial, antimicrobial, anticancer, antineoplastic, antidiabetic, antimalarial and antioxidant properties. A. muricata has more than 200 varieties of phytochemicals present, such as alkaloids, phenols, flavonoids, and acetogenins. Acetogenins have been identified as one of the main bioactive components of A. muricata, responsible for its anticancer potential. The phenolic compounds present in A. muricata, such as quercetin and gallic acid, are the main compounds that give it its antioxidant capacity. These compounds are what allow you to neutralize free radicals and protect cells from oxidative damage [19].

In the present work, the effect of A. muricata leaves extract as a green corrosion for aluminum in 20% ethanol-80% gasoline blend solution was investigated using weight loss and electrochemical techniques.

2.1. Testing material

The material used in this study was aluminum rod with a purity of 99.999%. For electrochemical tests, samples with a diameter of 0.64 cm and a length of 1 cm were prepared. The samples were subjected to a sanding process, using SiC emery paper from 120 to 3000 grade. To remove any sanding residue, the samples were rinsed with distilled water, followed by an additional cleaning using an ultrasonic bath.

2.2 Test fuel

The fuel used for the tests consisted of a blend of 20% sugarcane ethanol with a purity of 99.8% and 80% commercial unleaded gasoline.

2.3 Preparation of Inhibitor

A. muricata leaves were subjected to a maceration process, in which the dry leaves were crushed and immersed in 99.8% methanol. After 30 days, the resulting liquid was filtered and immediately allowed to evaporate at room temperature until a greenish solid extract was obtained.

Once the extract was obtained, the inhibitor was prepared using a solution with a concentration of 2000 ppm from 0.2 g of A. muricata extract and distilled water. Subsequently, this solution was added to the electrolyte solution at concentrations of 0, 5, 10, 20, 25 and 50 ppm.

2.4 Weight loss measurements

For weight loss measurements, Al samples with a diameter of 0.64 cm and a length of 1 cm were used. The samples were subjected to a sanding process, using SiC emery paper to a mirror finish, then rinsed with distilled water and cleaned using an ultrasonic bath for 10 min. They were then weighed and placed in 20% ethanol – 80% gasoline fuel blend, without and with the different concentrations of inhibitor for 91 days at room temperature. Subsequently, the samples were cleaned to eliminate corrosion products with 5 washing cycles, using nitric acid, according to the ASTM G1 standard and the weight loss, ΔW, was determined. Finally, the samples were characterized by SEM/EDS. Inhibitor efficiency, I.E., was calculated as follows:

$$I.E.\left( \% \right)=\frac{{\Delta {W_2} - \Delta {W_1}}}{{\Delta {W_2}}} \times 100$$

where ΔW₂ and ΔW₁ are the weight loss in absence and presence of the inhibitor respectively. At each inhibitor concentration, the tests were repeated three times.

2.5 Electrochemical measurements

All electrochemical measurements were carried out on an ACM Instruments potentiostat/galvanostat. A standard three-electrode electrochemical cell was used, in which a graphite bar was used as an auxiliary electrode, an Ag/AgCl electrode as a reference electrode and an Al specimen as a working electrode. The electrolyte consisted in 20% ethanol – 80% gasoline fuel blend at room temperature. Open circuit potential (OCP) measurements were recorded over an interval of 1800 s. Subsequently, linear polarization resistance (LPR) tests were performed in a potential range of -15 mV + 15 mV with a scan rate of 60 mV/s. Electrochemical impedance spectroscopy (EIS) tests were performed in a frequency range of 0.1 Hz to 10000 Hz, by applying a signal with an amplitude of ± 10 mV. Electrochemical noise (EN) measurement was performed in both current and potential simultaneously in blocks of 1024 readings taking a reading/s. Noise in current readings was taken by using a nominally identical working electrode, whereas the noise in potential was taken by using the Ag/AgCl reference electrode. All these tests were carried out for corrosion potential (E_corr) every week during 91 days.

2.6 Chemical characterization

The extract of A. Muricata leaves was characterized by Fourier transform infrared spectroscopy (FTIR) using a Varian 660-IR infrared (IR) spectrometer, the scanning absorption range was 1000 to 4000 cm^− 1 and gas chromatography coupled with mass spectrometry (GC-MS) by using an Agilent Technology 6890 gas chromatograph coupled to a 5973N mass detector.

2.7 Surface characterization

To analyze the morphology of the surface of Al immersed in 20% ethanol – 80% gasoline fuel blend, without and with different concentrations of inhibitor for 91 days, a Hitachi SU1510 Scanning Electron Microscope (SEM) was used. Chemical analysis was also performed using energy-dispersive X-ray spectroscopy (EDX).

3.1 Characterization of Annona muricata extract.

The functional groups present in the extract of A. muricata leaves were determined by interpreting the FTIR spectrum (Fig. 1). The peak observed in the spectrum at 3330 cm^− 1 corresponds to the characteristic stretching of the functional group -OH present in alcohols and phenols. The peaks observed at 2922 and 2851 cm^− 1 can be attributed to the methylene, -CH₂, and methyl, -CH₃, terminal groups of the fatty acids contained in the A. muricata extract. The peak present at 1621 cm^− 1 is related to the stretching of the C = O bond, indicating the presence of carboxylic acids, esters, and ketones. The peak at 1442 cm^− 1 showed the presence of aromatic compounds corresponding to the C = C stretching.

The GC-MS analysis identified the active compounds present in the A. muricata extract, which are detailed in Table 1 according to their retention times, RT. The presence of phenolic compounds, such as Phen-1,4, -diol, 2,3-dimethyl-5-trifluoromethyl and arbutin was identified, which have antioxidant properties, as it contribute to the reduction of reactive oxygen species levels and eliminate free radicals [20]. The presence of methyl esters of fatty acids was detected, such as lauric acid (Dodecanoic acid, 3-hydroxy), palmitic acid (Hexadecanoic acid) and 5,8,11,14-Eicosatetraenoic acid. These compounds have antioxidant, anti-inflammatory, and antimicrobial properties [21, 22]. On the other hand, methyl esters of linoleic acid were identified, such as 7,10-Octadecadiynoic and 9,12,15-Octadecatrienoic acids, which show antioxidant and anticancer properties [23]. The presence of terpenes such as R-Limonene and Curcurbitacin b is observed, which have been widely studied due to their strong anticancer activity and their ability to inhibit the growth of cancer cells [24]. Other compounds that exhibit antioxidant properties and have cancer-fighting potential have been identified, such as Vitamin E, Folic Acid, and Desulphosinigrin [25–27]. Some of these compounds, such as lauric acid, folic acid and vitamin E have been proven to be efficient corrosion inhibitors for different metals/environment combinations [28–30]. All these compounds are organic ones and contain heteroatoms within their structure such as N, S, O and P which share their free π electrons with the empty d orbitals of metals to form protective corrosion products onto the metal surface.

Table 1

GC-MS analysis of *Annona muricata* extract.
RT (min)	Component	Chemical formula
6.66–9.46	DL-Arabinose	C₅H₁₀O₅
10.44	1-Pentanol, 2-methyl-acetate	C₈H₁₆O₂
11.11	Folic Acid	C₁₉H₁₉N₇O₆
12.64–12.89	R-Limonene	C₁₀H₁₆O₃
13.23	Dodecanoic acid, 3-hidroxy	C₁₂H₂₄O₃
15.49–15.83	Desulphosinigrin	C₁₀H₁₇NO₆S
17.14	Arbutin	C₁₂H₁₆O₇
18.47	Hexadecanoic acid, methyl ester	C₁₃H₂₂O₂
18.99	1,1’-Bicyclopropyl-2-octanoic acid, 2’-hexil-, methyl ester	C₂₁H₃₈O₂
20.10	7,10-Octadecadiynoic acid, methyl ester	C₁₉H₃₄O₂
20.16	9,12,15-Octadecatrienoic acid, 2,3-dihydroxypropyl ester, (Z, Z, Z)-	C₃₆H₃₄O₄
20.37	5,8,11,14-Eicosatetraenoic acid, methyl ester	C₂₁H₃₄O₂
24.48	Phen-1,4-diol, 2,3- dimethyl-5-trifluromethyl	C₉H₉F₃O₂
27.59	1,3-Benzenedicarboxylic acid, bis (2-ethylhexyl) ester	C₂₄H₃₈O₄
29.18	Curcurbitacin b, 25-desacetoxy	C₃₀H₄₄O₆
31.55	1,2-Bis [1-(2-hydroxyethyl)-3,6-diazahomoadamantantydene	C₂₂H₃₆N₆O₂
32.59	Vitamin E	C₂₉H₅₀O₂

3.2. Gravimetric weight loss measurement

The effect of the inhibitor concentration (C_inh) on the weight loss (ΔW) and the inhibition efficiency (I.E.) on Al exposed to the 20% ethanol – 80% gasoline blend is shown in Fig. 2. A decrease in the Al corrosion rate is observed at all inhibitor concentrations, indicating that A. muricata extract delays the dissolution of Al in the ethanol-gasoline blend solution. This decrease in the Al weight loss is due to the adsorption of the A. muricata extract onto the metal to form a layer of corrosion products which protects the metal from corrosion. The lowest weight loss value, and thus, was obtained with an inhibitor concentration of 20 ppm, however, above this concentration, an increase in the weight loss rate is observed compared to lower concentrations. This increase suggests the possibility that absorbed and unabsorbed molecules interact, causing desorption [31]. The inhibition efficiency reaches its maximum value of 69% at the concentration of 20 ppm, indicating that at this concentration the greatest coverage of the Al surface with the inhibitor molecules is achieved.

To describe the adsorption behavior of A. muricata extract onto the Al surface, several adsorption isotherms, such as Langmuir, Frumkin, and Temkin, were used. The adsorption of the inhibitor involves the displacement of the water molecules from the metal surface by the inhibitor molecules according to following mechanism:

$$In{h_{(sol)}}+n{H_2}{O_{(ads)}} \to In{h_{(ads)}}+n{H_2}{O_{(sol)}}$$

where Inh_(sol) and Inh_(ads) stand for the inhibitor molecules in solution and adsorbed on the metal surface, and n is the number of water molecules. In this study, it was found that the Langmuir isotherm demonstrated a better fit to the experimental data according to the correlation coefficient R² of 0.95 (Fig. 3). This implies that the adsorbed inhibitor molecules are distributed homogeneously on the Al surface, forming a monolayer and there is not interaction among their molecules [32]. Mathematical expression of the Langmuir adsorption isotherm that relates the surface coverage of the inhibitor, θ, which is given by dividing the inhibitor efficiency value by 100, and the inhibitor concentration is presented by Eq. 3 as follows:

$$\frac{{{C_{inh}}}}{\theta }=\frac{1}{{{K_{ads}}}}+{C_{inh}}$$

where K_ads is the adsorption equilibrium constant, it is determined by Eq. 4:

$${K_{ads}}=\frac{\theta }{{{C_{inh}}\left( {1 - \theta } \right)}}$$

K_ads is fundamental in determining the standard adsorption Gibbs free energy (ΔGº_ads), which remains constant regardless of the degree of coverage. The ΔGº_ads, is defined by Eq. 5:

$$\Delta G_{{ads}}^{ \circ }= - RTIn{K_{ads}}{C_{{H_2}O\left( {aq} \right)}}$$

where C_H2O(aq) is the concentration of water in the electrolyte solution. The molarity of water at 25 ºC is 55.5 M. It is established that if ΔGº_ads is greater than − 20 kJ/mol, this indicates physical adsorption, while if ΔGº_ads is less than − 40 kJ/mol, it is considered chemical adsorption [33, 34]. The ΔGº_ads value for this study was − 28.03 kJ/mol, which is an indication that the adsorption process of A. muricata extract on the Al surface is a mixture of physical and chemical dominated by a weak, physical type of adsorption, whereas the negative sign means that this process is spontaneous. This process indicates the electrostatic interaction, which consists of the attraction of opposite charges between the inhibitor molecules and the metal surface, leading to the formation of a protective layer. However, the presence of various compounds in the extract implies the possibility of a chemical interaction between the metal and the π electrons involved in both the double bonds and free electrons present in the phenolic, nitrogenous, and heterocyclic compounds, terpenes, carboxylic acids. and esters that constitute the inhibitor molecules [35].

3.3 Electrochemical tests

3.3.1 OCP

The evolution of the Open circuit potential value, E_OCP, with time for Al immersed in the 20% ethanol – 80% gasoline blend solution, without and with A. muricata extract is shown in Fig. 4. In the absence of the inhibitor, the E_OCP value decreases from − 0.35 V to -0.43 V over 1800 s. The shift toward a slightly more negative E_OCP value may be related to the reaction of Al and ethanol. According to Song et al., in the absence of water, ethanol causes the corrosion of Al through an alkoxidation reaction [36] where oxygen will react with ethanol to form acetic acid and water plus according to [37]:

$${C_2}{H_5}OH+{O_2} \to C{H_3}COOH+{H_2}O$$

Because the ethanol-gasoline blend has a high resistivity, acetic acid will corrode Al not in an electrochemical way, but in a chemical way that produces hydrogen gas and aluminum acetate:

$$Al+C{H_3}COOH \to Al{\left( {C{H_3}COO} \right)_3}+{H_2}$$

Corrosion process will be enhanced by water and will produce protective layers of corrosion products, such as bayerite (Al(OH)₃) or boehmite (AlOOH). The addition of the inhibitor causes a decrease in the E_OCP value in the presence of 5 ppm, moving towards more active values from − 0.46 V to -0.48 V, indicating a greater susceptibility to corrosion, which can be attributed to a limited adsorption of the inhibitor. However, at concentrations of 10 ppm an increase in the E_OCP value is observed compared to the concentration of 5 ppm. At concentrations of 20 ppm and 25 ppm, a slight variation in the E_OCP values is evident, ranging between − 0.26 V to -0.32 V with a stable behavior. At a concentration of 50 ppm, the noblest potential is observed from − 0.28 V to 0.03 V with a trend towards more positive values as the immersion time passes. This shift of the E_OCP value into the noble direction is due to the formation of a protective layer of corrosion products onto Al due to the adsorption of A. muricata extract which suggests a greater protection provided by the inhibitor due to its ability to adsorb on the Al surface.

3.3.2 LPR experiments

The linear polarization resistance (LPR) technique was used to determine the polarization resistance (R_p). The value of Rp can be used to calculate the corrosion current, which is inversely proportional to Rp, according to the Stern-Geary Eq. (8):

$${i_{corr}}=\frac{B}{{{R_p}}}$$

Where B is a constant which depends upon the anodic and cathodic Tafel slopes, β_a and β_c respectively, according to following expression [38]:

$$B=\frac{{{\beta _a}{\beta _c}}}{{2.303({\beta _a}+{\beta _b})}}$$

In the present study, the variation of R_p with time at different concentrations of the A. muricata extract over the Al exposed to the 20% ethanol-80% gasoline blend solution was evaluated as shown in Fig. 5. This figure shows that the R_p values of Al without corrosion inhibitor fluctuate between 1.2 x10⁷ and 2.3 x10⁸ ohm cm² over time, indicating the formation and desorption of an aluminum oxide layer, Al₂O₃, on the surface of the material. When adding the A. muricata extract to concentrations higher than 5 ppm, an increase in the R_p values is observed due to the formation of a protective layer of corrosion products onto the metal surface, although some fluctuations ranging between 1.6 x10⁷ and 9.5 x10⁸ ohm cm² can be observed. These fluctuations are to the adsorption/desorption processes of the corrosion products layer from the Al surface. It is evident that the highest R_p value during the first weeks of exposure is obtained with an inhibitor concentration between 25 and 50 ppm; however, as exposure time continues, towards the end of the test, the highest R_p values are obtained with an inhibitor concentration of 25 ppm due to the inhibitor degradation and desorption from the Al surface. It is evident that A. muricata extract provides protection to Al during the whole time of exposure and continues to demonstrate its effectiveness after 90 days. These results demonstrate the adsorption capacity of the molecules present in the A. muricata extract.

3.3.3 Electrochemical Impedance Spectroscopy (EIS)

To have an insight on the corrosion mechanism for Al in the ethanol-gasoline blend solution in the absence and in the presence of different concentrations of the A. muricata extract, EIS diagrams in both the Nyquist and Bode representations, obtained after 7 and 91 immersion, are represented in Fig. 6 and Fig. 7 respectively. The Nyquist diagram after 7 days of immersion is shown in Fig. 6a, where it can be observed the presence of a single depressed, capacitive semicircle at high and low frequencies, indicating that the corrosion process is controlled by charge transfer. The addition of the inhibitor at all concentrations does not modify the shape of the spectra, indicating that the corrosion mechanism remains unaltered by the addition of the inhibitor, and is controlled by the transfer of electrons through the double electrochemical layer. The diameter of the semicircle increased in the presence of the inhibitor, reaching its maximum value when 50 ppm of A. muricata extract was added. This indicates the formation of a protective layer formed by the adsorption of the inhibitor on the metal surface, which increases the corrosion resistance of Al in the ethanol-gasoline blend solution.

On the other hand, bode plots in the modulus-frequency mode (Fig. 6b), shows that the impedance modulus values increased with the addition of the inhibitor, reaching values between 10⁷ and 10⁸ ohm cm², but there is a decrease in the concentration of 25 ppm, the protective layer formed on the metal surface may be desorbed in this case. In the bode phase angle diagram (Fig. 6b), broader peaks can be observed at low frequencies with the addition of the inhibitor at all concentrations, where the phase angle remained constant over a wide interval of frequencies, which implies the presence of at least two time constants and at the frequency intermediate, the phase angle is close to 90º, which represents the capacitive behavior of the Al surface. According to the literature, a phase angle of 90º corresponds to an ideal capacitive behavior indicating a metal covered by a very protective corrosion products layer [39].

After 91 days of immersion, Nyquist diagrams (Fig. 7a), a single capacitive semicircle can be observed at all frequency values without and with the A. muricata extract, indicating that the corrosion mechanism is still controlled by charge transfer. With the addition of the inhibitor, the diameter of the semicircle increased at all concentrations, which means that the dissolution of Al in the ethanol-gasoline blend solution decreased considerably. This is attributed to the adsorption of the A. muricata extract molecules on the metal surface.

The bode plots (Fig. 7b) show higher impedance modulus values than those obtained after an exposure time of 7 days at all inhibitor concentrations, this indicates an improvement in protection over time that may be due to the continuous formation of a protective layer on the metal surface that acts as a barrier that reduces the transport of corrosive species to the Al surface. The phase angle (Fig. 7b) remains almost constant over a wide intervals of frequency values, with values close to -90, which is characteristic of the capacitive response of a compact protective film.

The data obtained by EIS were simulated using an equivalent electrical circuit model, as shown in Fig. 8. In this figure, R_s represents the solution resistance, R_ct is the charge transfer resistance, CPE_dl is a phase element constant that replaces the electrochemical double layer capacitance (C_dl), due to surface roughness, non-uniform distribution of current during the corrosion process and inhomogeneous distribution of reaction rates on the electrode surface [40]. R_f and CPE_F are the resistance and constant phase element related to the capacitance of the corrosion products film formed on the Al surface, respectively. The electrochemical impedance of the constant phase element follows Eq. (6):

$${Z_{CPE}}=\frac{1}{{Q{{\left( {J\omega } \right)}^n}}}$$

where Q is a constant associated with the double layer capacitance, j=√-1 is the imaginary unit, ω is the angular frequency and n represents the empirical exponent with values between − 1 and 1. The value of n is related to the electrode surface heterogeneity in relation to the electrochemical response of the EIS measurement. A value of n = 1 corresponds to an ideal capacitor behavior, n = 0 to an ideal resistance and n=-1 to an ideal inductance [41, 42].

Electrochemical parameters obtained by simulating the EIS data are shown in Tables 2 and 3. The efficiency of A. muricata extract (I.E.%) according to the EIS parameters can be evaluated by Eq. (7):

$$I.E.(\% )=\frac{{{R_{ct}} - R_{{ct}}^{ \circ }}}{{{R_{ct}}}} \times 100$$

where R_ct and R^º_ct represent the charge transfer resistance in the presence and absence of the A. muricata extract. Results given in Tables 2 and 3 show high values of R_s that can be attributed to a higher percentage of gasoline in the blend, resulting in an increase in the solution resistivity. The presence of A. muricata extract reduces the CPE_dl value due to the replacement of water molecules by the adsorbed organic molecules of the A. muricata extract at the metal-solution interface, which leads to an increase in the thickness of the electrochemical double layer because the inhibitor molecules size is higher than that for water, since, according to the following expression, the double electrochemical layer capacitance is given by:

$${C_{dl}}=\left( {\frac{{\varepsilon {\varepsilon _0}}}{\lambda }} \right)A$$

where ε₀ is the free space permittivity, ε the dielectric constant of that space, λ the thickness of the double layer, and A the electrode surface area. An increase in the thickness of the double layer leads to a decrease in the C_dl value [43]. On the other hand, the reduction in the CPE_f value is due to an increase in the film resistance value, R_f, when the inhibitor is added since these parameters are inversely proportional.

Generally speaking, the R_ct values were higher than those for R_f, and this is due to the low dissolution rate of Al in this environment, which implies a low diffusion of Al³⁺ ions through the double electrochemical layer. The values for R_ct and R_f increase from values of 10⁷ to 10⁸ ohm cm² in the presence of the A. muricata extract, indicating the adsorption of organic molecules to the Al surface. In addition, R_f and R_ct increase after 91 days of immersion in the ethanol-gasoline blend solution (Table 4). This suggests the formation of a more resistant protective layer on the surface of the metal that decreases the corrosion rate of Al. The values of n_dl and n_f are close to 1, which indicates a low heterogeneity on the surface of Al due to a low metal corrosion rate and a behavior capacitive. The inhibitory efficiency reaches a value of 94% at concentrations of 20 ppm and 25 ppm after 91 days of immersion. These concentrations agree with the results of greater efficiency obtained in the gravimetric measurement of weight loss.

Table 2

Electrochemical parameters used to simulate EIS data for Al exposed to the 20% ethanol-80% gasoline blend solution with different concentrations of *A. muricata* extract after 7 days of immersion.
C_inh (ppm)	R_s (ohm cm²)	CPE_dl (F/cm²)	n_dl	R_f (ohm cm²)	CPE_f (F/cm²)	n_f	R_ct (ohm cm²)	I.E. (%)
0	479	2.99 x 10^− 9	1.0	9.81 x 10⁶	1.06 x 10^− 8	0.9	3.13 x 10⁷	---
5	422	2.48 x 10^− 9	1.0	2.28 x 10⁷	2.28 x 10^− 7	0.9	1.04 x 10⁸	70
10	489	2.84 x 10^− 9	1.0	5.06 x 10⁷	5.10 x 10^− 8	0.9	4.84 x 10⁷	35
20	133	2.74 x 10^− 9	1.0	4.25 x 10⁷	1.36 x 10^− 9	0.9	7.65 x 10⁷	60
25	591	4.24 x 10^− 9	1.0	5.94 x 10⁶	3.41 x 10^− 8	0.8	2.09 x 10⁷	-50
50	480	2.54 x 10^− 9	1.0	3.27 x 10⁷	1.17 x 10^− 9	0.9	2.07 x 10⁸	85

Table 3

Electrochemical parameters used to simulate EIS data for Al exposed to the 20% ethanol-80% gasoline blend solution with different concentrations of *A. muricata* extract after 91 days of immersion.
C_inh (ppm)	R_s (ohm cm²)	CPE_dl (F/cm²)	n_dl	R_f (ohm cm²)	CPE_f (F/cm²)	n_f	R_ct (ohm cm²)	I.E. (%)
0	359	3.73 x 10^− 9	1.0	7.84 x 10⁷	1.22 x 10^− 8	0.9	1.25 x 10⁸	---
5	405	3.61 x 10^− 9	1.0	1.35 x 10⁸	1.39 x 10^− 8	0.9	4.52 x 10⁸	38
10	401	3.13 x 10^− 9	1.0	3.03 x 10⁸	5.08 x 10^− 9	0.9	1.75 x 10⁹	93
20	461	3.43 x 10^− 9	1.0	1.39 x 10⁹	1.71 x 10^− 9	1.0	2.15 x 10⁹	94
25	330	3.65 x 10^− 9	1.0	1.16 x 10⁹	2.68 x 10^− 8	0.9	1.93 x 10⁹	94
50	334	3.07 x 10^− 9	1.0	3.47 x 10⁸	1.21 x 10^− 9	0.9	1.23 x 10⁹	90

3.3.4 Electrochemical noise (EN)

The time noise series in current and potential obtained for Al after an immersion time of 91 days in the ethanol-gasoline blend solution and in the absence and presence of different concentrations of A. muricata extract are shown in Fig. 9.

In the absence of the inhibitor (Fig. 9a), low-frequency current transients in the order of 10^− 8 mA/cm² are observed, which are characterized by a rapid increase in current followed by a slow drop in current. These types of transients indicate the formation of a localized type of corrosion such a pitting, due to the breakdown of a passive layer formed on the metal surface when an increase in current occurs and a slow repassivation when the current decreases [44]. In the time series of electrochemical noise in potential, low-intensity transients are observed with a tendency towards more noble potentials that can be attributed to the ability of Al to form a passive layer of aluminum oxide on its surface.

With the addition of the A. muricata extract (Figs. 9b-9f), the current density decreases in the order of up to 10^− 9, that is, the A. muricata extract adsorbs to the Al surface, forming a layer of corrosion products much more resistant to be broken down, and thus, reducing the susceptibility to pitting corrosion. In the time series but in the potential, a trend towards more noble potentials is observed at all concentrations of the inhibitor, which indicates a lower susceptibility of aluminum to corrode in the 20% ethanol-80% gasoline blend solution in the presence of the inhibitor.

The noise resistance (R_n) was calculated by the ratio of the standard deviation in potential, σ_E, and the standard deviation in the noise in current, σ_I, (Eq. 9) [45].

$${R_n}=\frac{{{\sigma _E}}}{{{\sigma _I}}}$$

Figure 10 shows the results obtained for the noise resistance of Al in relation to the concentration of the A. Muricata extract during 91 days of immersion in the ethanol-gasoline blend solution. The R_n values increased in the presence of the inhibitor in the order of 10⁸ ohm cm², which are in agreement with the values obtained for R_p and R_ct obtained in the linear polarization resistance and electrochemical impedance spectroscopy techniques, respectively, which is very encouraging.

3.4 SEM analysis

The Figs. 11 and 12 show the SEM micrographs and microchemical EDS analysis, respectively, of aluminum immersed in an 20% ethanol-80% gasoline blend solution without and with the optimal studied concentration of the A. muricata extract after 91 days. In the absence of the inhibitor (Fig. 11a), the presence of corrosion products can be observed as a protective oxide layer of Al₂O₃ formed. However, due to the instability of the protective layer, pitting may be noticed on the surface of the aluminum. These results are confirmed through EDS analysis (Fig. 12a), which reveals the detection of O y Al in the sample, indicating the presence of Al₂O₃ as part of the formation process of the protective layer. The presence of C in the sample could be due to the presence of acetic acid that is formed during the oxidation process of ethanol [46, 47].

With the addition of the inhibitor at the concentration of 20 ppm (Figs. 11b), no pits are observed on the surface, instead, black spots are observed that can be attributed to a possible interaction of the inhibitor with the metal surface. The EDS analysis (Fig. 12b) shows a decrease in the percentage of oxygen. In addition, an increase in the C contents was detected, which is attributed to the presence of organic compounds present in the Annona muricata extract adsorbed on the aluminum surface. These results indicate that the addition of A. muricata extract as an inhibitor has a positive effect on the reduction of Al corrosion in the 20% ethanol-80% gasoline blend solution due to the formation of an additional protective layer, thanks to the action of the inhibitor, on the already existing film of Al₂O₃.

The effect of Annona muricata leaves extract as a green corrosion inhibitor for aluminum in 20% ethanol-80% gasoline blend solution was investigated. Results have shown that Annona muricata extract is an efficient corrosion inhibitor, with an efficiency that increases with its concentration, reaching a maximum value with the addition of 20 and 25 ppm. The adsorption of the A. muricata extract on the aluminum surface obeyed the Langmuir adsorption isotherm and occurred mainly through physisorption. This adsorption leads to an increase in the R_p value due to the increase in the formed film thickness, and also to an increase in the R_ct value due to a decrease in the metal corrosion rate and a lower amount of metallic ions crossing across the double electrochemical layer. Noise resistance data have indicated that the adsorption of Annona muricata extract decreases the Al pitting corrosion susceptibility. FTIR and GC-MS analyses of A. muricata extract show the presence of phenolic compounds, lauric acid, palmitic acid, linoleic acid, vitamin E and other compounds, most of which exhibit antioxidant properties. SEM images demonstrated a reduction in pitting corrosion in the presence of the inhibitor.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Data availability statement

Data are included in the article; further inquiries can be directed to the corresponding author.

Competing Interests

The authors have no relevant financial or non-financial interests to disclose.

Author Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Dinora A. Nogueiron Benitez and José G. Gonzalez Rodriguez, software by Roy Lopez Sesenes and validation by America M. Ramirez Arteaga. The first draft of the manuscript was written by Ana K. Larios Galvez and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Orege JI, Oderinde O, Kifle GA, Ibikunle AA, Raheem SA, Ejeromedoghene O, Okeke ES, Olukowi OM, Orege OB, Fagbohun EO, Ogundipe TO, Avor EP, Ajayi OE, Daramola MO (2022) Recent advances in heterogeneous catalysis for green biodiesel production by transesterification. Energy Convers Manag 258:115406. https://doi.org/10.1016/j.enconman.2022.115406
Rajak J (2021) A Preliminary Review on Impact of Climate change and our Environment with Reference to Global Warming. Int J Environ Sci 10(1):11–14
Ramos M, Dias APS, Puna J, Gomes J, Bordado J (2019) Biodiesel Production Processes and Sustainable Raw Materials. Energies 12(23):4408. https://doi.org/10.3390/en12234408
Khan MAH, Bonifacio S, Clowes J, Foulds A, Holland R, Matthews J, Percival CJ, Shallcross DE (2021) Investigation of Biofuel as a Potential Renewable Energy Source. Atmosphere 12(10):1289. https://doi.org/10.3390/atmos12101289
Melendez JR, Mátyás B, Hena S, Lowy D, El Salous A (2022) Perspectives in the production of bioethanol: A review of sustainable methods, technologies, and bioprocesses. Renew Sustain Energy Rev 160:112260. https://doi.org/10.1016/j.rser.2022.112260
Tse TJ, Wiens DJ, Reaney MJT (2021) Production of Bioethanol—A Review of Factors Affecting Ethanol Yield. Fermentation 7:268. https://doi.org/10.3390/fermentation7040268
Rony ZI, Mofijur M, Hasan M, Rasul M, Jahirul M, Ahmed SF, Kalam MA, Badruddin IA, Khan TMY, Show P (2023) Alternative fuels to reduce greenhouse gas emissions from marine transport and promote UN sustainable development goals. Fuel 338:127220. https://doi.org/10.1016/j.fuel.2022.127220
Shaikh MZA (2020) A Review on Biodiesel as an Alternative Fuel for Diesel Engine Applications. Int j res appl sci eng Technol 8:941–964. https://doi.org/10.22214/ijraset.2020.31622
Göktaş M, Balki M, Sayin C, Canakci M (2021) An evaluation of the use of alcohol fuels in SI engines in terms of performance, emission and combustion characteristics: A review. Fuel 286:119425. https://doi.org/10.1016/j.fuel.2020.119425
Kumar TS, Ashok B (2023) Corrosion behaviour analysis of SI engine components for ethanol-gasoline blends in flex fuel vehicular application. Fuel Process. Technol. 240:107574. https://doi.org/10.1016/j.fuproc.2022.107574
Baena LM, Vásquez F, Calderón JA (2021) Corrosion assessment of metals in bioethanol-gasoline blends using electrochemical impedance spectroscopy. Heliyon 7(7):07585. https://doi.org/10.1016/j.heliyon.2021.e07585
Longanesi L, Pereira AP, Johnston N, Chuck CJ (2021) Oxidative stability of biodiesel: recent insights. Biofpr 16(1):265–289. https://doi.org/10.1002/bbb.2306
Niculescu RM, Clenci A, Iorga-Simăn V (2019) Review on the Use of Diesel–Biodiesel–Alcohol Blends in Compression Ignition Engines. Energies 12(7):1194. https://doi.org/10.3390/en12071194
Baroš P, Matějovský L, Macák J, Staš M, Pospı́Šil M (2022) Corrosion Aggressiveness of Ethanol–Gasoline and Butanol–Gasoline Blends on Steel: Application of Electrochemical Impedance Spectroscopy. Energy Fuels 36(5):2616–2629. https://doi.org/10.1021/acs.energyfuels.1c03680
Macák J, Matějovský L, Pleyer O, Arnoult-Růžičková M, Jelínek L (2022) Passivation of steel in ethanol–gasoline blends induced by diethylene triamine. Electrochim Acta 434:141263. https://doi.org/10.1016/j.electacta.2022.141263
Matějovský L, Macák J, Pleyer O, Straka P, Staš M (2019) Efficiency of Steel Corrosion Inhibitors in an Environment of Ethanol–Gasoline Blends. ACS Omega 4(5):8650–8660. https://doi.org/10.1021/acsomega.8b03686
Katuwal P, Regmi RS, Joshi S, Bhattarai J (2020) Assessment on the Effective Green-Based Nepal Origin Plants Extract as Corrosion Inhibitor for Mild Steel in Bioethanol and its Blend. Eur J Adv Chem Res 1(5). https://doi.org/10.24018/ejchem.2020.1.5.16
Vu NSH, Hiến PV, Mathesh M, Thu VTH, Nam NĐ (2019) Improved Corrosion Resistance of Steel in Ethanol Fuel Blend by Titania Nanoparticles and Aganonerion polymorphum Leaf Extract. ACS Omega 4(1):146–158. https://doi.org/10.1021/acsomega.8b02084
Chan WJ, McLachlan AJ, Hanrahan JR, Harnett J (2019) The safety and tolerability of Annona muricata leaf extract: a systematic review. J Pharm Pharmacol 72(1):1–16. https://doi.org/10.1111/jphp.13182
Boo YC (2021) Arbutin as a Skin Depigmenting Agent with Antimelanogenic and Antioxidant Properties. Antioxidants 10(7):1129. https://doi.org/10.3390/antiox10071129
Liu T, Su G, Yang T (2021) Functionalities of chitosan conjugated with lauric acid and l-carnitine and application of the modified chitosan in an oil-in-water emulsion. Food Chem 359:129851. https://doi.org/10.1016/j.foodchem.2021.129851
Nengroo ZR, Rauf A (2019) Fatty acid composition and antioxidant activities of five medicinal plants from Kashmir. Ind Crops Prod 140:111596. https://doi.org/10.1016/j.indcrop.2019.111596
Ukwubile C, Ahmed A, Katsayal U, Ya'u J, Mejida S (2019) GC-MS analysis of bioactive compounds from Melastomastrum capitatum (Vahl) Fern. leaf methanol extract: An anticancer plant. Sci Afr 3:e00059. https://doi.org/10.1016/j.sciaf.2019.e00059
Dai S, Wang C, Zhao X, Ma C, Fu K, Liu Y, Peng C, Li Y (2023) Cucurbitacin B: A review of its pharmacology, toxicity, and pharmacokinetics. Pharmacological Research 187 (2023):106587. https://doi.org/10.1016/j.phrs.2022.106587
Youssef A, Maaty D, Al-saraireh Y (2022) Phytochemistry and Anticancer Effects of Mangrove (Rhizophora mucronata Lam.) Leaves and Stems Extract against Different Cancer Cell Lines. Pharmaceuticals 16:4. https://doi.org/10.3390/ph16010004
Jiao Z, Wang X, Yin Y, Xia J (2018) Preparation and evaluation of vitamin C and folic acid-coloaded antioxidant liposomes. Part Sci Technol 37(4):453–459. https://doi.org/10.1080/02726351.2017.1391907
Abraham A, Kattoor A, Saldeen T, Mehta J (2018) Vitamin E and its anticancer effects. Crit Rev Food Sci Nutr 59:01–23. https://doi.org/10.1080/10408398.2018.1474169
Fuchs-Godec R, Zerjav G (2015) Corrosion resistance of high-level-hydrophobic layers in combination with Vitamin E – (α-tocopherol) as green inhibitor. Corros Sci 97:7–16. https://doi.org/10.1016/j.corsci.2015.03.016
Xu W, Wei J, Yang Z, Xu P, Yu Q (2020) Feasibility and corrosion inhibition efficacy of zeolite-supported lauric acid imidazoline as corrosion inhibitor in cementitious mortar. Constr Building Mater 250:118861. https://doi.org/10.1016/j.conbuildmat.2020.118861
Van Der Mei HC, Song H, Feng K, Chen Y, Yan H, Luo C, Liu D, Guan H, Chassagne L, Hu Z (2023) Corrosion protection of folic acid and lauric acid modified films prepared by anodic oxidation on WE43 magnesium alloys. Appl Surf Sci 638:158014. https://doi.org/10.1016/j.apsusc.2023.158014
Alhaffar MT, Umoren SA, Obot I, Ali SA (2018) Isoxazolidine derivatives as corrosion inhibitors for low carbon steel in HCl solution: experimental, theoretical and effect of KI studies. RSC Adv 8(4):1764–1777. https://doi.org/10.1039/c7ra11549k
Kalam S, Abu-Khamsin S, Kamal MS, Patil S (2021) Surfactant Adsorption Isotherms: A Review. ACS Omega 6:32342–32348. https://doi.org/10.1021/acsomega.1c04661
Kokalj A (2023) On the use of the Langmuir and other adsorption isotherms in corrosion inhibition. Corros Sci 217:111112. https://doi.org/10.1016/j.corsci.2023.111112
Vaszilcsinc CG, Putz MV, Kellenberger A, Dan ML (2023) On the evaluation of metal-corrosion inhibitor interactions by adsorption isotherms. J Mol Struct 1286:135643. https://doi.org/10.1016/j.molstruc.2023.135643
Salman TA, Al-Amiery AA, Shaker LM, Aadhum A, A H, Takriff MS (2019) A study on the inhibition of mild steel corrosion in hydrochloric acid environment by 4-methyl-2-(pyridin-3-yl) thiazole-5-carbohydrazide. Int J Corros Scale Inhib 8(4):1035–1059. https://doi.org/10.17675/2305-6894-2019-8-4-14
Song G, Liu M (2013) Corrosion and electrochemical evaluation of an Al–Si–Cu aluminum alloy in ethanol solutions. Corros Sci 72:73–81. https://doi.org/10.1016/j.corsci.2013.03.009
Marinov NM (1999) A detailed chemical kinetic model for high temperature ethanol oxidation. Int J Chem Kinet 31(3):183–220. https://doi.org/10.1002/(sici)1097-4601(1999)31:3
Sohail MG, Laurens S, Deby F, Balayssac J, Al-Nuaimi N (2021) Electrochemical corrosion parameters for active and passive reinforcing steel in carbonated and sound concrete. Mater Corros 72(12):1854–1871. https://doi.org/10.1002/maco.202112569
Kaushik RK, Batra U, Sharma J (2021) Electrochemical Corrosion Behavior of Sn–1.0Ag–0.5Cu and Sn–3.8Ag–0.7cu Lead Free Solder Alloys During Storage and Transportation Under Chloride Working Condition. Trans Electr Electron Mater 23(4):371–381. https://doi.org/10.1007/s42341-021-00354-9
Sadeghi S, Ebrahimifar H (2021) Effect of Electrolyte pH on Microstructure, Corrosion Behavior, and Mechanical Behavior of Ni-P-W-TiO2 Electroplated Coatings. J Mater Eng Perform 30(4):2409–2421. https://doi.org/10.1007/s11665-021-05462-4
Ouassir J, Bennis H, Benqlilou H, Galai M, Hassani Y, Touhami ME, Berrami K, Lemyasser M (2020) EIS study on erosion–corrosion behavior of BA35 and BA22 brasses in drinking water at various impingement angles. Colloids Surf A: Physicochem Eng Asp 586:124151. https://doi.org/10.1016/j.colsurfa.2019.124151
Protsenko VS, Butyrina TE, Bobrova L, Korniy S, А, Данилов, Ф И (2020) Enhancing corrosion resistance of nickel surface by electropolishing in a deep eutectic solvent. Mater Lett 270:127719. https://doi.org/10.1016/j.matlet.2020.127719
Fadhil AA, Khadom AA, Ahmed SK, Liu H, Fu C, Mahood HB (2020) Portulaca grandiflora as new green corrosion inhibitor for mild steel protection in hydrochloric acid: Quantitative, electrochemical, surface and spectroscopic investigations. Surf Interfaces 20:100595. https://doi.org/10.1016/j.surfin.2020.100595
Li T, Jun W, Frankel GS (2021) Localized corrosion: Passive film breakdown vs. Pit growth stability, Part VI: Pit dissolution kinetics of different alloys and a model for pitting and repassivation potentials. Corros Sci 182:109277. https://doi.org/10.1016/j.corsci.2021.109277
Zhang Z, Wang B, Zhao Z, Li X, Liu B, Bai P (2022) Effect of chloride ion concentration on corrosion process of selective laser melted AlSi10Mg with different heat treatments studied by electrochemical noise. J Mater Res Technol 16:1597–1609. https://doi.org/10.1016/j.jmrt.2021.12.102
Lin C, Ma L (2020) Influences of Water Content in Feedstock Oil on Burning Characteristics of Fatty Acid Methyl Esters. Processes 8(9):1130. https://doi.org/10.3390/pr8091130
Gonzalez GG, Zonetti PC, Silveira EB, De Souza Nogueira Sardinha Mendes F, De Avillez RR, Rabello CR, Zotin FMZ, Appel LG (2019) Two mechanisms for acetic acid synthesis from ethanol and water. J Catal 380:343–351. https://doi.org/10.1016/j.jcat.2019.09.031

No competing interests reported.

Download PDF

Editorial decision: Revision requested
10 Sep, 2024
Reviews received at journal
31 Aug, 2024
Reviews received at journal
28 Aug, 2024
Reviewers agreed at journal
23 Aug, 2024
Reviewers agreed at journal
21 Aug, 2024
Reviewers invited by journal
21 Aug, 2024
Submission checks completed at journal
02 May, 2024
Editor assigned by journal
02 May, 2024
First submitted to journal
30 Apr, 2024

You are reading this latest preprint version

A Study of the corrosion inhibition of aluminum in ethanol-gasoline blend by using Annona muricata leaves extract

Status:

Version 1

Abstract

Figures

1. Introduction

2. Experimental

2.1. Testing material

2.2 Test fuel

2.3 Preparation of Inhibitor

2.4 Weight loss measurements

2.5 Electrochemical measurements

2.6 Chemical characterization

2.7 Surface characterization

3. Results

3.1 Characterization of Annona muricata extract.

3.2. Gravimetric weight loss measurement

3.3 Electrochemical tests

3.3.1 OCP

3.3.2 LPR experiments

3.3.3 Electrochemical Impedance Spectroscopy (EIS)

3.3.4 Electrochemical noise (EN)

3.4 SEM analysis

4. Conclusions

Declarations

References

Additional Declarations

Status:

Version 1