Corrosion Behavior of Aluminium-Coated Cans

Hundreds of billions of aluminium-based cans are manufactured and used every year worldwide including those containing soft drinks. This study investigates and evaluates the performance and quality of two well-known energy and soft drinks brands, Green Cola and Red Bull. Recent health hazards and concerns have been associated with aluminium leakage and bisphenol A (BPA) dissociation from the can’s internal protective coating. The cans were examined under four conditions, including coated and uncoated samples, the soft drink’s main solution, and 0.1 M acetic acid solution. Electrochemical measurements such as potentiodynamic polarization and impedance spectroscopy (EIS), element analyses using inductively coupled plasma optical emission spectrometry (ICP-OES), and energy dispersive X-ray spectroscopy (EDS) were performed. In addition, sample characterization by scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) were employed to comprehensively study and analyze the effect of corrosion on the samples. Even though the internal coating provided superior corrosion protection concerning main or acetic acid solutions, it failed to prevent aluminium from dissolving in the electrolyte. Green Cola’s primary solution appears to be extremely corrosive, as the corrosion rate increased by approximately 333% relative to the acetic acid solution. Uncoated samples resulted in increases in the percentage of oxygen, the appearance of more corrosion spots, and decreases in crystallinity. The ICP-OES test detected dangerous levels of aluminium in the Green Cola solution, which increased significantly after increasing the conductivity of the solution.


Introduction
Aluminium (Al) is a common industrial metal, especially in beverage and food packaging. The inclusion of more electropositive components in soft drinks, such as chloride and copper ions, facilitates the corrosion of aluminium and its alloys [1]. Although aluminium is a relatively corrosion-impervious metal, drinks with a low pH can dissolve the aluminium oxide layer, which serves as a natural passivation layer. Since the invention of the metal can more than two centuries ago, the globe produces more than 250 billion of them annually [2]. Leaking metal from cans into drinks can cause Alzheimer's, Parkinson's, and multiple sclerosis. Aluminium food and drink containers have a thin polymer coating or internal coating layer to reduce metal-to-product contact and corrosion. Thin-layer corrosion protection includes vinylic or phenolic lacquers and epoxy resins [3]. Marijan Seruga and Damir Hasenay say aluminium leaching into soft drinks is a slow, time-dependent process influenced by PH level and brand [4]. Oxygen concentration in the package; pH; product composition; dissolved salts, ions, and molecules; and the environment, temperature, and pressure all affect metal corrosion. Depolarizing oxygen and dissolved ions accelerate corrosion [5].

Characterization
SEM (JEOL JSM-IT300LV, JEOL, Tokyo, Japan) with 100×, 250×, 500× and 1000× magnification) was used to examine aluminium alloy samples before and after corrosion. ICP-OES (inductively coupled plasma-optical emission spectrometry), an analytical technique in which the concentration of elements in (mostly water-dissolved) samples could be determined, was employed for Green Cola and Red Bull solutions.

Samples
Initially, a 1 cm 2 sheet cut from both Geen Cola and Red Bull cans. For the coated samples, the 1 cm 2 directly transferred to the corrosion electrochemical cell without any further preparation. However, for the uncoated samples, the inner coating was removed by polishing the samples with SiC paper 1200. It should be noted that the exposed area of the working electrode is 0.785 cm 2 . Samples were examined in terms of two types of corrosion electrolytes; namely the main solution for the drink (MS) or in acetic acid (Ac-OH). The samples were named as follows: MS-WC denotes samples examined in the main solution with the presence of an internal coating (WC).
MS-WOC denotes samples examined in the main solution without the presence of an internal coating (WOC). The same procedures were applied to acetic acid.
The content of Red Bull as labeled on the can is as follows: a Red Bull beverage can produced in Switzerland, filled by Rauch Trading AG, Widnau, Switzerland for Red Bull GmbH, Fuschl am See, Austria. Its nutrition information per 100 mL contains the following: water, sugar, glucose, citric acid, carbon dioxide, taurine (400 mg/100 mL), acidity regulator sodium bicarbonate, natural and artificial flavours (vanilla, pineapple, berries), acidity regulator magnesium carbonate, colour caramel, caffeine (32 mg/100 mL), niacin, pantothenic acid, vitamin B6, colour riboflavin, vitamin B12.
Furthermore, 1 M KCl as a supporting electrolyte was added to all tested solutions to enhance the solution conductivity.

Electrochemical Experiments
Electrochemical experiments were performed using a traditional three-electrode flat cell containing a platinum mesh as a counter electrode, an Ag/AgCl/KClsat as a reference electrode, and a working electrode with the surface of 0.785 cm 2 . An SP-200 potentiostat (BioLogic Company, Grenoble, France) was employed to run four electrochemical experiments at room temperature using EC Laboratory software for data fitting. Initially, an open circuit potential was measured for 1 h. Subsequently, electrochemical impedance spectroscopy measurements were obtained using an AC signal at an open-circuit potential in the 10 −1 to 10 5 Hz frequency range by the application of a sinusoidal voltage at ±10 mV. Additionally, double-layer capacitance (Q), F.s (n−1) .cm −2 , was calculated using the following formula [14]: GmbH, Fuschl am See, Austria. Its nutrition information per 100 mL contains the follo ing: water, sugar, glucose, citric acid, carbon dioxide, taurine (400 mg/100 mL), acid regulator sodium bicarbonate, natural and artificial flavours (vanilla, pineapple, berri acidity regulator magnesium carbonate, colour caramel, caffeine (32 mg/100 mL), nia pantothenic acid, vitamin B6, colour riboflavin, vitamin B12. Furthermore, 1 M KCl as a supporting electrolyte was added to all tested soluti to enhance the solution conductivity.

Electrochemical Experiments
Electrochemical experiments were performed using a traditional three-electrode cell containing a platinum mesh as a counter electrode, an Ag/AgCl/KClsat as a refere electrode, and a working electrode with the surface of 0.785 cm 2 . An SP-200 potentio (BioLogic Company, Grenoble, France) was employed to run four electrochemical exp iments at room temperature using EC Laboratory software for data fitting. Initially open circuit potential was measured for 1 h. Subsequently, electrochemical impeda spectroscopy measurements were obtained using an AC signal at an open-circuit poten in the 10 −1 to 10 5 Hz frequency range by the application of a sinusoidal voltage at ±10 m Additionally, double-layer capacitance (Q), F.s (n−1) .cm −2 , was calculated using the follo ing formula [14]: Y0 is a proportional factor, ꙍ is the angular frequency at the maximum impeda of the imaginary axis, and n is a deviation factor from −1 to +1 from a pure inductor pure capacitor. Then, potentiodynamic polarization was performed at a scan rate of 0. mV/s and different working electrode potentials of +500 mV and −250 mV with respec OCP.
The corrosion current density icorr is calculated using the following formula [15]: where i, E, Ecorr, bc, and ba are the current density, applied potential, corrosion poten cathodic Tafel slope, and anodic Tafel slope, respectively, which are calculated using Laboratory software for data fitting. The corrosion rate (rcorr in mils per year, mpy,) was calculated based on the follow [16]: where icorr, MW, , and n represent the corrosion current density (µA cm −2 ), atomic m of aluminium alloy 3004 (g/mol), sample density (g/cm 3 ), and number of electrons changed by the corrosion reaction, respectively. Finally, a cyclic polarization scan fr +500 mV to −250 mV with respect to OCP at a scan rate of 1 mV/s was performed hysteresis analyses and examination of localized corrosion susceptibility.

Open Circuit Potential
One-hour open circuit potential curves for Green Cola and Red Bull can samples w (WC) and without (WOC) organic coating are shown in Figures 1 and 2 Y 0 is a proportional factor, GmbH, Fuschl am See, Austria. Its nutrition information per 100 mL contains the following: water, sugar, glucose, citric acid, carbon dioxide, taurine (400 mg/100 mL), acidity regulator sodium bicarbonate, natural and artificial flavours (vanilla, pineapple, berries), acidity regulator magnesium carbonate, colour caramel, caffeine (32 mg/100 mL), niacin, pantothenic acid, vitamin B6, colour riboflavin, vitamin B12. Furthermore, 1 M KCl as a supporting electrolyte was added to all tested solutions to enhance the solution conductivity.

Electrochemical Experiments
Electrochemical experiments were performed using a traditional three-electrode flat cell containing a platinum mesh as a counter electrode, an Ag/AgCl/KClsat as a reference electrode, and a working electrode with the surface of 0.785 cm 2 . An SP-200 potentiostat (BioLogic Company, Grenoble, France) was employed to run four electrochemical experiments at room temperature using EC Laboratory software for data fitting. Initially, an open circuit potential was measured for 1 h. Subsequently, electrochemical impedance spectroscopy measurements were obtained using an AC signal at an open-circuit potential in the 10 −1 to 10 5 Hz frequency range by the application of a sinusoidal voltage at ±10 mV. Additionally, double-layer capacitance (Q), F.s (n−1) .cm −2 , was calculated using the following formula [14]: Y0 is a proportional factor, ꙍ is the angular frequency at the maximum impedance of the imaginary axis, and n is a deviation factor from −1 to +1 from a pure inductor to a pure capacitor. Then, potentiodynamic polarization was performed at a scan rate of 0.166 mV/s and different working electrode potentials of +500 mV and −250 mV with respect to OCP.
The corrosion current density icorr is calculated using the following formula [15]: where i, E, Ecorr, bc, and ba are the current density, applied potential, corrosion potential, cathodic Tafel slope, and anodic Tafel slope, respectively, which are calculated using EC Laboratory software for data fitting. The corrosion rate (rcorr in mils per year, mpy,) was calculated based on the following [16]: where icorr, MW, , and n represent the corrosion current density (µA cm −2 ), atomic mass of aluminium alloy 3004 (g/mol), sample density (g/cm 3 ), and number of electrons exchanged by the corrosion reaction, respectively. Finally, a cyclic polarization scan from +500 mV to −250 mV with respect to OCP at a scan rate of 1 mV/s was performed for hysteresis analyses and examination of localized corrosion susceptibility.

Open Circuit Potential
One-hour open circuit potential curves for Green Cola and Red Bull can samples with (WC) and without (WOC) organic coating are shown in Figures 1 and 2, respectively.
Under the premise that the film is porous, the open circuit potential values for Green Cola and Red Bull samples in the presence of organic coating (i.e., as made) indicate fluctuating and unstable values during the immersion time for both samples. However, more stable and accurate open circuit potential values were obtained for uncoated cans, as seen m is the angular frequency at the maximum impedance of the imaginary axis, and n is a deviation factor from −1 to +1 from a pure inductor to a pure capacitor. Then, potentiodynamic polarization was performed at a scan rate of 0.166 mV/s and different working electrode potentials of +500 mV and −250 mV with respect to OCP.
The corrosion current density i corr is calculated using the following formula [15]: where i, E, E corr , b c , and b a are the current density, applied potential, corrosion potential, cathodic Tafel slope, and anodic Tafel slope, respectively, which are calculated using EC Laboratory software for data fitting. The corrosion rate (r corr in mils per year, mpy), was calculated based on the following [16]: where i corr , MW, ρ, and n represent the corrosion current density (µA cm −2 ), atomic mass of aluminium alloy 3004 (g/mol), sample density (g/cm 3 ), and number of electrons exchanged by the corrosion reaction, respectively. Finally, a cyclic polarization scan from +500 mV to −250 mV with respect to OCP at a scan rate of 1 mV/s was performed for hysteresis analyses and examination of localized corrosion susceptibility.

Open Circuit Potential
One-hour open circuit potential curves for Green Cola and Red Bull can samples with (WC) and without (WOC) organic coating are shown in Figures 1 and 2

Electrochemical Impedance Spectroscopy
Because of its adaptability and precision, electrochemical impedance spectroscopy (EIS) is frequently used in corrosion studies to examine the corrosion performance of coated metals [17]. EIS measurements were conducted to examine the degradation of the internal organic coating in main (MS) and acetic acid (AcOH) solutions.

Electrochemical Impedance Spectroscopy
Because of its adaptability and precision, electrochemical impedance spectroscopy (EIS) is frequently used in corrosion studies to examine the corrosion performance of coated metals [17]. EIS measurements were conducted to examine the degradation of the internal organic coating in main (MS) and acetic acid (AcOH) solutions.

Electrochemical Impedance Spectroscopy
Because of its adaptability and precision, electrochemical impedance spectroscopy (EIS) is frequently used in corrosion studies to examine the corrosion performance of coated metals [17]. EIS measurements were conducted to examine the degradation of the internal organic coating in main (MS) and acetic acid (AcOH) solutions. paper, resistance values in both axes dropped drastically over the supplied frequency d main, as illustrated in the Figures' insets (see Figures 3 and 4). This indicates that the i ternal organic coating serves a significant function from a corrosion protection point view.  The data acquired from the impedance spectra provided in Figures 3 and 4 were the fitted to an analogous electric circuit, namely a simplified Randles cell, for uncoated sam ples and a two-time constants circuit for coated samples, as depicted in Figure 5. Figu ternal organic coating serves a significant function from a corrosion protection poin view.  The data acquired from the impedance spectra provided in Figures 3 and 4 were th fitted to an analogous electric circuit, namely a simplified Randles cell, for uncoated sa ples and a two-time constants circuit for coated samples, as depicted in Figure 5. Fig The data acquired from the impedance spectra provided in Figures 3 and 4 were then fitted to an analogous electric circuit, namely a simplified Randles cell, for uncoated samples and a two-time constants circuit for coated samples, as depicted in Figure 5. Figure 5a,b are well-known models used for intact and damaged coated metals, respectively [12,18]. 5a,b are well-known models used for intact and damaged coated metals, respectiv [12,18]. These cell models account for solution resistance (Rs), double-layer capacita (CPE1), and (CPE2) for n < 1 meaning a non-ideal capacitor, where R2 the resistance of coating to the transfer of ions, C1 ideal capacitor for coating as an organic isolator and and (R3) are charge transfer resistances of the polished aluminium metal and expo metal through conductive paths of the coating and oxide layers, respectively. One pressed semicircle, which is indicative of a single charge-transfer, is clearly present for uncoated samples. However, for coated samples, the diffusion process predominate low frequencies, leading to noisy behaviour and ill-defined segments. Tables 1 and 2 s marize the data derived from impedance spectra using the parameters listed there. Coated samples of Green Cola and Red Bull showed double layer capacitance va significantly higher than those observed with polished samples. This signifies that m ionization occurred on the surfaces without the internal organic coating. In addition, polarization resistance (R3) values for Green Cola and Red Bull samples with organic c ing (WS) are much higher compared with Rp values without a coating (WOC), rang from 31 to 1349 folds for Green Cola's main and Red Bull's AcOH solutions, respectiv These cell models account for solution resistance (Rs), double-layer capacitance (CPE 1 ), and (CPE 2 ) for n < 1 meaning a non-ideal capacitor, where R 2 the resistance of the coating to the transfer of ions, C 1 ideal capacitor for coating as an organic isolator and (R p ) and (R 3 ) are charge transfer resistances of the polished aluminium metal and exposed metal through conductive paths of the coating and oxide layers, respectively. One depressed semicircle, which is indicative of a single charge-transfer, is clearly present for the uncoated samples. However, for coated samples, the diffusion process predominates at low frequencies, leading to noisy behaviour and ill-defined segments. Tables 1 and 2 summarize the data derived from impedance spectra using the parameters listed there. solutions were more corrosive for coated samples. The impedance results for Green Cola are comparable to those reported for cola-flavored soft drinks [12].

Polarization Measurements
Following open circuit potential measurements, potentiodynamic polarizations were conducted to evaluate the corrosion resistance of the samples under four conditions (MS-WC, MS-WOC, AcOH-WC, and AcOH-WOC). Representative Tafel plots are depicted in Figure 6. The corrosion current density and corrosion rate values were extracted from each polarization curve and are summarized in Table 3.
Materials 2023, 16, x FOR PEER REVIEW An indication of smoother surfaces is a slight rise in n values for uncoated sampl cording to Rp values, acetic acid addition was detrimental to uncoated samples, w main solutions were more corrosive for coated samples. The impedance results for Cola are comparable to those reported for cola-flavored soft drinks [12].

Polarization Measurements
Following open circuit potential measurements, potentiodynamic polarization conducted to evaluate the corrosion resistance of the samples under four condition WC, MS-WOC, AcOH-WC, and AcOH-WOC). Representative Tafel plots are depi Figure 6. The corrosion current density and corrosion rate values were extracted fro polarization curve and are summarized in Table 3.  The samples from Green Cola examined in the main solution of the soft drin WOC) had the highest corrosion current density with an icorr of 41.3 µAcm −2 , wher same samples in the AcOH-WOC solution had a lower corrosion current density w icorr of 7.5 µAcm −2 , as depicted in Figure 6a. This indicates that the Green Cola soft main solution is more corrosive than acetic acid alone. The uncoated samples of R (4.3 mpy) showed a lower corrosion current density compared with Green Cola (17. in main solutions, and the coated samples had a comparable contrast. Overall, th ence of the internal organic coating reduced the corrosion rate by 80 to 99%. Accor organic-coated Green Cola and Red Bull samples demonstrated greater corros sistance, while samples without the organic coating showed an increase in curre decreased corrosion resistance ( Table 3). The samples studied in acetic acid displ negative shift in the corrosion potential for both types. This was probably related  The samples from Green Cola examined in the main solution of the soft drink (MS-WOC) had the highest corrosion current density with an i corr of 41.3 µAcm −2 , whereas the same samples in the AcOH-WOC solution had a lower corrosion current density with an i corr of 7.5 µAcm −2 , as depicted in Figure 6a. This indicates that the Green Cola soft drink's main solution is more corrosive than acetic acid alone. The uncoated samples of Red Bull (4.3 mpy) showed a lower corrosion current density compared with Green Cola (17.7 mpy) in main solutions, and the coated samples had a comparable contrast. Overall, the presence of the internal organic coating reduced the corrosion rate by 80 to 99%. Accordingly, organic-coated Green Cola and Red Bull samples demonstrated greater corrosion resistance, while samples without the organic coating showed an increase in current and decreased corrosion resistance ( Table 3). The samples studied in acetic acid displayed a negative shift in the corrosion potential for both types. This was probably related to an increase in the acidity close to the surface. Therefore, this resulted in an increase in H + ion concentration and cathodic current. E corr values were almost identical regardless of the presence or absence of the organic coating owing to porous or damaged coating. Samples of Red Bull showed similar results, but to a lesser extent.

Cyclic Polarization
The polarization was carried out with and without the organic coating, as shown in Figures 7 and 8. Several observations can be noticed. At both electrolytes, organic coated samples exhibit more negative corrosion potential, although the difference in the potential (∆E) between corrosion potential (E corr ) and re-passivation potential (E rep ) remains similar. E rep lies on nobler voltages than E corr for all samples, indicating aluminum oxide formation, but to a lesser extent for samples in acetic acid solutions owing to the higher acidity of the solution. Moreover, the measured current density of samples without an organic coating is higher than that of samples with an organic coating. In addition, the hysteresis loop in the presence of the organic coating is wider, thereby implying enhanced corrosion protection.
Materials 2023, 16, x FOR PEER REVIEW 8 increase in the acidity close to the surface. Therefore, this resulted in an increase in H concentration and cathodic current. Ecorr values were almost identical regardless o presence or absence of the organic coating owing to porous or damaged coating. Sam of Red Bull showed similar results, but to a lesser extent.

Cyclic Polarization
The polarization was carried out with and without the organic coating, as show Figures 7 and 8. Several observations can be noticed. At both electrolytes, organic co samples exhibit more negative corrosion potential, although the difference in the pote (ΔE) between corrosion potential (Ecorr) and re-passivation potential (Erep) remains sim Erep lies on nobler voltages than Ecorr for all samples, indicating aluminum oxide forma but to a lesser extent for samples in acetic acid solutions owing to the higher acidity o solution. Moreover, the measured current density of samples without an organic co is higher than that of samples with an organic coating. In addition, the hysteresis lo the presence of the organic coating is wider, thereby implying enhanced corrosion pr tion.  increase in the acidity close to the surface. Therefore, this resulted in an increase in concentration and cathodic current. Ecorr values were almost identical regardless presence or absence of the organic coating owing to porous or damaged coating. Sa of Red Bull showed similar results, but to a lesser extent.

Cyclic Polarization
The polarization was carried out with and without the organic coating, as sho Figures 7 and 8. Several observations can be noticed. At both electrolytes, organic samples exhibit more negative corrosion potential, although the difference in the po (ΔE) between corrosion potential (Ecorr) and re-passivation potential (Erep) remains s Erep lies on nobler voltages than Ecorr for all samples, indicating aluminum oxide form but to a lesser extent for samples in acetic acid solutions owing to the higher acidity solution. Moreover, the measured current density of samples without an organic c is higher than that of samples with an organic coating. In addition, the hysteresis l the presence of the organic coating is wider, thereby implying enhanced corrosion p tion.

Scanning Electron Microscopy (SEM)
A non-corroded contact blank sample, with and without a coating, is shown in Figure 9. As depicted in Figures 10-13

Scanning Electron Microscopy (SEM)
A non-corroded contact blank sample, with and without a coating, is shown in Figure  9. As depicted in Figures 10-13, the morphology of the samples was examined following corrosion tests in both main (MS) and acetic acid [0.1 M] solutions.  Figure  9b showed almost pure aluminium. Furthermore, EDS analysis in Figure 10 shows a still high carbon percentage, but increased aluminum for coated samples (C = 70.2, Al = 19.2, O = 9.3), whereas in the absence of the coating, carbon and oxygen also spiked, implying the formation of corrosion products (C = 39.7, Al = 45.2, O = 11.1). Similar trends are observed in Figures 11-13. In addition, aluminium alloy constituents, such as mg, Cu, Mn, and Fe, are more prevalent after corrosion for coated samples, as a result of coating failure (see . Figure 13a illustrates a Red Bull AcOH WC sample with the most intact coating and fewest corrosion products. In accordance with Table 1's high impedance resistance, an increase in oxygen content could indicate the formation of aluminium oxide.       Figure 9b showed almost pure aluminium. Furthermore, EDS analysis in Figure 10 shows a still high carbon percentage, but increased aluminum for coated samples (C = 70.2, Al = 19.2, O = 9.3), whereas in the absence of the coating, carbon and oxygen also spiked, implying the formation of corrosion products (C = 39.7, Al = 45.2, O = 11.1). Similar trends are observed in Figures 11-13. In addition, aluminium alloy constituents, such as mg, Cu, Mn, and Fe, are more prevalent after corrosion for coated samples, as a result of coating failure (see Figures 10-12). Figure 13a illustrates a Red Bull AcOH WC sample with the most intact coating and fewest corrosion products. In accordance with Table 1's high impedance resistance, an increase in oxygen content could indicate the formation of aluminium oxide.

Elemental Analysis
Analytical techniques such as inductively coupled plasma optical emission spectrometry (ICP OES) are useful for determining the concentration of components in samples [19]. ICP OES was performed with either Green Cola, Green Cola with KCl, or acetic acid with KCl solutions, whereby, KCl was added to improve conductivity. Leakage of aluminium was examined using ICP OES in this investigation. After an electrochemical corrosion test on Green Cola, the aluminium content leached into the main solution as a corrosion electrolyte was 0.75 ppm, which is above the accepted contamination level, 0.2 mg/l, stipulated by the Agency for Toxic Substances and Disease Registry (ATSDR) [20]. This content increased significantly to 20.70 ppm after using supporting electrolyte (KCl).

Elemental Analysis
Analytical techniques such as inductively coupled plasma optical emission spectrometry (ICP OES) are useful for determining the concentration of components in samples [19]. ICP OES was performed with either Green Cola, Green Cola with KCl, or acetic acid with KCl solutions, whereby, KCl was added to improve conductivity. Leakage of aluminium was examined using ICP OES in this investigation. After an electrochemical corrosion test on Green Cola, the aluminium content leached into the main solution as a corrosion electrolyte was 0.75 ppm, which is above the accepted contamination level, 0.2 mg/L, stipulated by the Agency for Toxic Substances and Disease Registry (ATSDR) [20]. This content increased significantly to 20.70 ppm after using supporting electrolyte (KCl). Furthermore, the amount of aluminium that leached from the Green Cola sample into acetic acid as a corrosion electrolyte was 13.20 ppm. Accordingly, solution conductivity and severity of content plays a significant role in soft drink can corrosion. The corrosion results in Table 3 and EDS analysis in Figure 10a are consistent with higher aluminium concentrations in the Green Cola main solution as determined by the (ICP OES) technique. Figure 14 represents the XRD of aluminium cans for Green Cola after corrosion in main and acetic acid solutions with and without a coating and a blank sample. All five figures display pure aluminium peaks, and a small peak appears for corroded samples as a result of impurities such as manganese, magnesium, and iron, which is highlighted by the arrow in the Figure [21]. The aluminium peaks at 2θ = 39.3, 45.5, 65.8, and 78.8 • in Figure 14 correspond to the pure aluminium profile in the literature (JCPDS number 89-4037) [22]. For the indexed peaks, there are three phases: boehmite (AlOOH) for 2θ = 39.3 and 65.8 • , face centred cubic aluminium for 2θ = 65.8 and 78.8 • , and cubic γ-Al2O3 for 2θ = 45.5 • [22]. Figure 14 clearly indicates that uncoated samples had lower crystallinity as the intensity of the (220) and (311) planes decreased owing to the corrosion of unprotected aluminium metal. In contrast, the uncoated samples' planes (111) and (200) peaks widened and remained the same, respectively, compared with the coated samples, which could be related to corrosion products' formation following aluminium oxidation. Green Cola coated samples showed an out of plane shift to lower angles because of the coating, which might indicate tensile stress of the sample reducing fault probabilities and strains [23]. The blank coated sample displayed lower crystallinity than the corroded ones, which may have been a result of the coating thickness thinning or failing during corrosion, allowing for the appearance of more intensified peaks. Figure 14 represents the XRD of aluminium cans for Green Cola after corrosion in main and acetic acid solutions with and without a coating and a blank sample. All five figures display pure aluminium peaks, and a small peak appears for corroded samples as a result of impurities such as manganese, magnesium, and iron, which is highlighted by the arrow in the Figure [21]. The aluminium peaks at 2θ = 39.3, 45.5, 65.8, and 78.8° in Figure 14 correspond to the pure aluminium profile in the literature (JCPDS number 89-4037) [22]. For the indexed peaks, there are three phases: boehmite (AlOOH) for 2θ = 39.3 and 65.8°, face centred cubic aluminium for 2θ = 65.8 and 78.8°, and cubic γ-Al2O3 for 2θ = 45.5° [22]. Figure 14 clearly indicates that uncoated samples had lower crystallinity as the intensity of the (220) and (311) planes decreased owing to the corrosion of unprotected aluminium metal. In contrast, the uncoated samples' planes (111) and (200) peaks widened and remained the same, respectively, compared with the coated samples, which could be related to corrosion products' formation following aluminium oxidation. Green Cola coated samples showed an out of plane shift to lower angles because of the coating, which might indicate tensile stress of the sample reducing fault probabilities and strains [23]. The blank coated sample displayed lower crystallinity than the corroded ones, which may have been a result of the coating thickness thinning or failing during corrosion, allowing for the appearance of more intensified peaks.

Conclusions
In this investigation, aluminium cans of Green Cola and Red Bull energy drinks were analyzed in two different solutions: main and 0.1 M acetic acid. The cans were examined both with and without the interior coating.
The coating provides substantial protection against corrosion in comparison with uncoated samples, as the corrosion rate was reduced by 80 to 99 percent based on Tafel plots,

Conclusions
In this investigation, aluminium cans of Green Cola and Red Bull energy drinks were analyzed in two different solutions: main and 0.1 M acetic acid. The cans were examined both with and without the interior coating.
The coating provides substantial protection against corrosion in comparison with uncoated samples, as the corrosion rate was reduced by 80 to 99 percent based on Tafel plots, and the polarization resistance obtained for EIS results increased by three orders of magnitude or more. The coating protects the metal, as evidenced by the increased intensity of aluminium peaks in coated samples, as determined by XRD results. It was discovered, despite the fact that the coating lessens the corrosion caused by the Green Cola primary solution, that the solution is still extremely corrosive.
Similar open circuit potential values between coated and uncoated samples, two time constants impedance model involving metal participation in the reaction, aluminum leakage detection from ICP OES test, grey areas in SEM images representing corrosion products, and increasing aluminum percentage detected by EDS analysis all indicate that the coating failed to fully prevent aluminum from contaminating the drinks. Data Availability Statement: All the raw data supporting the conclusion of this paper were provided by the authors.