Sustainable additives for corrosion protective coatings for substrates

Abstract

The present invention relates to sustainable additives for corrosion protective coatings for substrates. The present disclosure relates to methods, systems, and apparatuses for imparting corrosion protective properties to coatings for aluminum, aluminum alloys, copper, and copper alloys by preparing and applying a corrosion inhibiting formulation containing a plant extract that includes the corrosion protective properties.

Description

[0001] This application is a divisional application of the patent application filed on December 27, 2017, with application number 2017114413906, entitled "Sustainable Additive for Anti-corrosion Coatings for Substrates". Technical Field

[0002] This disclosure generally relates to the field of corrosion inhibitors for use with aluminum, aluminum alloys, copper, and copper alloys. More specifically, this disclosure relates to corrosion-resistant compositions and methods for manufacturing corrosion-resistant compositions that do not contain hexavalent chromium. Background Technology

[0003] Currently, industry continues to respond to strong regulatory needs to eliminate the use of compounds considered environmentally toxic and carcinogenic. Representative compounds include hexavalent chromium used in conjunction with corrosion inhibitors. Consequently, there is a need to identify chromium alternatives that offer sufficient or superior corrosion inhibition compared to unpopular chromium formulations.

[0004] The list of potential alternatives to chromium-containing compounds—which could be viable compounds exhibiting a predetermined degree of corrosion inhibition—is large. However, identifying viable corrosion-inhibiting candidates requires extensive testing and a corresponding amount of experimentation and funding to conduct such testing.

[0005] It would be advantageous to have corrosion-resistant coating alternatives that have corrosion resistance close to or exceeding that of corrosion-resistant coatings containing hexavalent chromium, along with the methods used to manufacture them. Summary of the Invention

[0006] This disclosure relates to methods for inhibiting corrosion of a substrate, comprising applying a composition to the substrate, wherein the composition comprises an extract derived from a plant genus, including: *Annona squamosa* (…). Annona ), Inca genus ( Inga Mango (genus) Mangifera ); Dandelion ( Taraxacum ); Bidens genus ( Bidens ); Plantago asiatica ( Plantango ); Matricaria ( Chamomilla Solidago ( ); Goldenrod genus ( Solidago ), and combinations thereof; and the inhibition of corrosion of the substrate, wherein the substrate includes the substrate surface.

[0007] On the other hand, in the step of applying the composition to the substrate, the composition includes an extract derived from a plant species, including: Annona squamosa (…). Annona crassiflora ); Inca bean (a certain type); mango ( Mangifera indica ); custard apple ( Annona squamosa ); Western dandelion ( Taraxacum officinale ); Bidens trifoliata ( Bidens pilosa ); Plantain (long-leaved plantain) Plantango major ); Matricaria ( Chamomilla recutita Chilean goldenrod ( Solidago chilensis ); and its combination.

[0008] In another aspect, in the step of applying the composition to the substrate, the composition includes extracts derived from plant species, including: custard apple, custard apple, mango, beggar-ticks, and combinations thereof.

[0009] In another aspect, in the step of applying the composition to the substrate, the composition includes an extract derived from a plant species, including custard apple, sweet custard apple, mango, beggar-ticks, and combinations thereof, wherein the extract is present in the composition at a concentration ranging from about 5% to about 20%.

[0010] On the other hand, in the step of applying the composition to the substrate, the substrate includes aluminum, aluminum alloys, copper, copper alloys, and combinations thereof.

[0011] In a further aspect, the substrate includes aluminum alloy 2024 T3 or aluminum alloy 7075.

[0012] In a further aspect, this disclosure considers compositions for inhibiting corrosion on substrates, wherein the compositions comprise extracts derived from plant genera including Annuae, Inca Inca, Mango, Taraxacum, Bidens, Plantago, Matricaria, Solidago, and combinations thereof.

[0013] On the other hand, the composition includes plant-derived extracts selected from plant species including Annona squamosa; Inca bean (a certain species); mango; Annona squamosa; dandelion; Bidens trifoliata; Plantago asiatica; Matricaria champaca; Solidago camara; and combinations thereof.

[0014] On the other hand, the composition includes extracts derived from plant species, including custard apple, mango, and others. Mangifera indica L ); Bidens trifoliata; and its combination.

[0015] On the other hand, the composition includes a plant-derived extract selected from plant species including Annona squamosa, Annona squamosa, Bidens trifoliata, and combinations thereof, wherein the extract is present in the composition at a concentration ranging from about 5% to about 20%.

[0016] On another aspect, the composition includes extracts derived from plant genus, which are extracted from plant seeds, plant pulp, plant bark, plant leaves, and combinations thereof.

[0017] On the other hand, the composition further includes a primer.

[0018] In another aspect, the composition further includes a primer comprising a polyurethane compound.

[0019] On the other hand, compositions including the plant extracts described above are additives incorporated into coating formulations.

[0020] Further aspects involve coatings for inhibiting corrosion, wherein the coatings include extracts derived from plant genera, including: Annuae, Inca Inca, Mango; Taraxacum; Bidens; Plantago; Matricaria; Solidago; and combinations thereof.

[0021] On the other hand, the coating includes plant-derived extracts, selected from plants including: custard apple; *Inca Inca* (a certain species); mango; custard apple; dandelion; beggar-ticks; plantain; matricaria; goldenrod; and combinations thereof.

[0022] On the other hand, the coating includes a composition comprising plant-derived extracts selected from custard apple, sweet custard apple, mango, beggar-ticks, and combinations thereof.

[0023] On the other hand, the coating includes a composition comprising an extract derived from a plant species, including custard apple, custard apple, mango, beggar-ticks, and combinations thereof, wherein the extract is present in the composition at a concentration ranging from about 5% to about 20%.

[0024] A further aspect of this disclosure relates to a substrate, which includes a coating for inhibiting corrosion on the substrate, wherein the coating includes extracts derived from plant genera, including: Annuae, Inca Inca, Mango; Taraxacum; Bidens; Plantago; Matricaria; Solidago; and combinations thereof.

[0025] In a further aspect, the base includes a coating comprising an extract derived from plant species, including: custard apple; *Inca Inca* (a certain species); mango; custard apple; dandelion; beggar-ticks; plantain; magnolia; goldenrod; and combinations thereof.

[0026] On the other hand, the base includes a coating comprising a composition having extracts derived from plant species including custard apple, custard apple, mango, beggar-ticks, and combinations thereof, wherein the extracts are present in the composition at a concentration ranging from about 5% to about 20%.

[0027] In a further aspect, the substrate includes aluminum, aluminum alloys, copper, copper alloys, and combinations thereof.

[0028] On the other hand, the substrate includes aluminum alloy 2024 T3, aluminum alloy 7075, and combinations thereof.

[0029] Further aspects involve objects having a base with a coating, wherein the coating comprises extracts derived from plant genera, including: Annuae, Inca Inca, Mango; Taraxacum; Bidens; Plantago; Matricaria; Solidago; and combinations thereof.

[0030] On the other hand, the object includes a substrate comprising a composition having extracts derived from plant species including custard apple, custard apple, mango, beggar-ticks, and combinations thereof, wherein the extracts are present in the composition at a concentration ranging from about 5% to about 20%.

[0031] In a further aspect, the object includes a stationary structure or a moving structure, wherein the moving structure includes, without limitation, vehicles.

[0032] On another aspect, means of transport include: manned aircraft, unmanned aircraft; manned spacecraft; unmanned spacecraft; manned rotorcraft; unmanned rotorcraft; manned land vehicles; unmanned land vehicles; manned water vehicles; unmanned water vehicles; manned underwater vehicles; unmanned underwater vehicles; and combinations thereof. Attached Figure Description

[0033] Having thus broadly described the variations of this disclosure, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which: Figure 1 It displays the current density (A / cm²). 2 The graph is plotted as a function of the applied potential (V) for a control compound sample, which is known to have antioxidant properties at a concentration of 1000 ppm. Figure 2 This is a graph showing the polarization curve (anodic scan) of the control compound sample—which is known to have antioxidant properties at a concentration of 1000 ppm—over 5000 s at -0.953 V; Figure 3 This is a graph showing the polarization curve (anodic scan) of the control compound sample—which is known to have antioxidant properties at a concentration of 1000 ppm—over 5000 s at -0.60 V; Figure 4 This is a graph showing the polarization curves (anodic scan) of the plant extract tested at a concentration of 1000 ppm against a control compound sample—which is known to have antioxidant properties—over 5000 s at -0.60 V; Figure 5 It displays the current density (A / cm²). 2The graph is plotted as a function of applied potential (V) for control compound samples known to have antioxidant properties at a concentration of 1000 ppm and plant extracts at a concentration of 1000 ppm. Figure 6 This is a graph showing the correlation between plant extract samples: the % DPPH free radical scavenging test of such samples as a function of % corrosion inhibition efficiency (% CIE); and Figure 7-11 This is a flowchart summarizing aspects of the content of this disclosure. Detailed Implementation

[0034] This disclosure relates to anti-corrosion compositions comprising specific plant extracts from plant genera and species—which have now been identified as possessing anti-corrosion properties and characteristics. A further aspect of this disclosure relates to coatings for substrates comprising anti-corrosion compositions, and methods for inhibiting corrosion on substrate surfaces, comprising applying the composition and coating to the substrate surface, particularly aluminum, aluminum alloys, copper, and copper alloy components.

[0035] It has now been determined that corrosion-resistant coatings can be successfully manufactured by incorporating compounds—including compounds extracted from naturally occurring plant species that exhibit antioxidant properties (e.g., “extracts”)—which are also equivalently referred to herein as “corrosion-inhibiting coatings.” Many naturally occurring antioxidant compounds have been found in and extracted from various plant species. However, not every candidate naturally occurring antioxidant compound will impart sufficient corrosion-resistant properties to the coating formulation for the purpose of inhibiting corrosion on a particular substrate material. “Sufficient corrosion-resistant properties” means that the corrosion-resistant properties are approximately equivalent to or greater than those of non-naturally occurring corrosion-resistant formulations, such as those containing hexavalent chromium compounds.

[0036] In fact, while many naturally occurring plant genera and species within such genera can exhibit some degree of antioxidant properties, it has been determined that not all such genera and species will produce extracts that impart sufficient anti-corrosion properties to anti-corrosion formulations for the purpose of inhibiting corrosion—inclusively including inhibiting corrosion on substrates including aluminum or aluminum alloys, copper or copper alloys, etc. Therefore, it may take considerable labor-intensive trial-and-error effort to obtain the necessary effective amount of extract from candidate plant genera or species for inclusion in anti-corrosion formulations to protect the substrate from corrosion, only to find that such anti-corrosion formulations provide substandard levels of corrosion protection to the substrate materials—e.g., aluminum, aluminum alloys, copper, copper alloys, etc.

[0037] According to this disclosure, methods for predictively selecting plant extracts from plant genera and species that will provide predetermined and quantifiable anti-corrosion properties to the anti-corrosion agent for the purpose of inhibiting corrosion of the substrate have now been discovered. Preferably, the substrate includes aluminum, aluminum alloys, copper, copper alloys, etc.

[0038] DPPH (diphenylpiccrylhydrazyl) is a stable and commercially available organic nitrogen radical with a maximum UV-visible absorbance at 517 nm. After reduction, the purple color of the DPPH solution fades, allowing the reaction to be colorimetrically monitored using a spectrophotometer. The loss of the initial purple color and the change to pale yellow indicates an increase in the solution's antioxidant capacity (i.e., free radical scavenging). This antioxidant capacity (i.e., free radical scavenging) is therefore expressed as the percentage of DPPH inhibition (%). The absorbance of blank / control DPPH solutions and DPPH solutions containing the sample is measured using a spectrophotometer. The amount of free radicals scavenged is obtained by subtracting the absorbance of the test solution (sample) from the absorbance of the blank DPPH solution.

[0039] According to this disclosure, selected plants are tested in DPPH assays and then submitted for linear sweep voltammetry and chronoamperometry analysis. A collection of compounds with known properties is sampled as “controls” to generate reference points. For example, thiophenol, containing a thiol group, is known to have satisfactory corrosion inhibition and is used as a control in electrochemical tests. According to this disclosure, at a potential maintained at -0.6 V, compared with thiophenol and other control reference points, plant extract samples found to be useful as additives to corrosion inhibitors applied to the substrate (and tested at concentrations ranging from 1 ppm to 1000 ppm) showed particularly good results at concentrations ranging from approximately 500 ppm to approximately 1000 ppm.

[0040] According to this disclosure, plants believed to possess some degree of antioxidant capacity were identified and collected, including those abundantly found in nature. More specifically, five (5) species from the Asteraceae family, three (3) species from the Annonaceae family, one (1) species from the Astropurpurea variety, and one (1) species from the Euphorbiaceae family were collected, separated into leaves, branches, fruits, pulp, peel, and seeds, and then submitted to the extraction process.

[0041] Further considerations for obtaining plant extracts include extracting plant extract samples by methods comprising: treating plant seeds, plant pulp, plant peel, or combinations thereof to obtain a sample; adding a solvent to the sample; and precipitating the dry extract from the solvent. It should be understood that the solvent is essentially removed from the sample. “Treatment” of the sample includes any chemical or physical process that can act to reduce a natural plant form (e.g., seeds, leaves, peel, etc.) to a simplified form. Such “treatment” is not limited to impregnation, grinding, etc. Further understanding, impregnation of the sample refers to the process of softening or breaking down the sample, typically by adding a solvent.

[0042] Further extraction was performed as follows. The aerial parts of *Bidens trifoliata*, *Taraxacum mongolicum*, and *Chaenomeles speciosa*, the seeds and peel of *Annona squamosa*, and the leaves of *Mangosteeniae* and *Solidago canadensis* were frozen, ground, and freeze-dried in liquid nitrogen prior to extraction. Extracts were obtained from the plant material by using polar organic solvents such as alcohols—methanol or ethanol—and ethanol mixed with water (also equivalently referred to as 70% ethanol and ethanol:water, 7:3 (v / v)). One (1.0 g) gram of plant material was extracted with three (3.0) mL of methanol for 20 minutes with stirring. Extraction was performed three times. The resulting combined liquid extract was evaporated under vacuum at 45°C. The obtained extract was kept at 4°C protected from light. For *Annona squamosa* peel, the best solvent extractant was an ethanol / water (7:3) solution, also referred to as 70% ethanol v / v. One (1.0 g) gram of plant material was extracted with three (3.0) mL of 70% ethanol v / v for 20 minutes with stirring. The extraction was performed three times. The resulting combined liquid extract was evaporated under vacuum at 50°C. The remaining water was freeze-dried and the extract was kept at 4°C in the dark.

[0043] Thirty-seven (37) plant extracts from five (5) different plant species were subjected to a diphenylpicrylhydrazone (DPPH) radical scavenging assay. Such a DPPH assay is based on the ability of the test to transfer electrons from a compound containing an antioxidant to an oxidant. Three plant samples exhibiting more than 60% DPPH radical scavenging efficiency were selected as potential antioxidant sources. In addition, thiophene, 2,5-dimercapto-1,3,4-thiadiazole, and 6-amino-2-mercaptobenzothiazole were also evaluated and established as controls in the DPPH radical scavenging assay, showing radical scavenging efficiencies of 90.69%, 88.55%, and 88.42%, respectively. α-Tocopherol (vitamin E), ascorbic acid (vitamin C), and gallic acid were also used as positive controls, showing radical scavenging efficiencies of 90.17%, 89.01%, and 88.80%, respectively.

[0044] It has now been determined that the results obtained from plant extract samples—which undergo 1) DPPH testing and 2) electrochemical techniques (linear sweep voltammetry and chronoamperometry analysis)—correlating with the determination of corrosion can accurately predict the efficacy of candidate materials for imparting corrosion-resistant properties to corrosion inhibitors—which are used on substrate materials including aluminum, aluminum alloys, copper, and copper alloys.

[0045] Although specific results obtained for samples subjected to 1) DPPH radical scavenging tests and 2) electrochemical techniques (linear sweep voltammetry and chronoamperometry analysis) may vary, it has been established that plant extracts possess corrosion-inhibiting properties when there is an approximately 1:1 (+ / - 10%) correlation between specific extract values ​​and when the value is approximately 80.00 or higher. These properties can be incorporated into corrosion inhibitors for aluminum and aluminum alloy substrates to inhibit corrosion of substrates including aluminum, aluminum alloys, copper, and copper alloys.

[0046] Examples 1-7 Compounds with anti-corrosion properties, such as thiophene, 2,5-dimercapto-1,3,4-thiadiazole, and 6-amino-2-mercaptobenzothiazole, were used as controls. Additionally, α-tocopherol, ascorbic acid, and gallic acid (Sigma-Aldrich) were used as standard compounds with known and recognized antioxidant activities.

[0047] DPPH Radical Scavenging Assay – Antioxidant assays were performed in a Thermo Scientific Spectrophotometer (MultiskanGO, processed with SkanIt Software 3.2.1.4RE) (Erkin, Cetin, and Ayranci, 2011; Roesler, Carharino, Malta, Eberlin & Pastore, 2007). The assay was performed on 96-well microplates using six (6) different concentrations of each substance (1000, 500, 250, 125, 62.5, and 31.25 µg / mL). 0.004% (w / v) of DPPH methanol solution (250 µL) was added to a methanol solution (10 µL) of the compound to be tested. Absorbance was measured at 517 nm after 30 min. Controls were prepared as above but without any extracts, and methanol was used for baseline correction. Radical scavenging was expressed as a percentage of inhibition and calculated via the following formula: %Corrosion Inhibition = [(A DPPH –A Ext ) / A DPPH ] ×0.100 Where ADPPH This is the absorbance value of the DPPH blank sample; A Ext It is the absorbance value of the extract sample, which is evaluated as the difference between the absorbance value of the extract sample and the absorbance value of the corresponding blank.

[0048] Rotating disk experiment – ​​Linear sweep voltammetry (LSV) was performed on a Pine Research Instrument using a copper disk electrode rotator rotating at 1000 rpm with a Series G-750 potentionstat, a platinum counter electrode, and a glass Colonel Ag / AgCl reference electrode. Gamry Framework software was used. Copper disk (1 cm²) 2 The working electrode (OD 10 mm) was used in conjunction with an electrode polished between readings. LSV was measured as a potential scan at a scan rate of 0.002 V / s between -0.157 V and -1.150 V. Air was introduced into the solution via a pump before measurement. The current decay over 5000 seconds was measured at -0.953 V. A current plateau was observed between -0.7 and -0.6 V for most commercially available (known) compounds. Since the current plateau can be an indicator of corrosion inhibitor function, chronoamperometry experiments were run at a potential maintained at -0.6 V. Solutions were prepared using phosphate-buffered saline (PBS) buffer tablets (Sigma P4417). The purity of 99%+ pure copper was verified using a Baird DV4 Arc / Spark luminescence spectrometer. Two different experiments were performed: 1. Measure the current based on the applied potential ranging from -0.157 V to -1.150 V; 2. Polarization curves (anodic scan) at -0.953 V during 5000 s and current decay over time at -0.6 V.

[0049] Initial experiments were conducted at the following concentrations: 1000, 500, 100, and 10 ppm. Experiments maintaining a potential of -0.6 V were performed at 1000 ppm. A blank sample (100 mL of PBS) was prepared before each experiment.

[0050] Calculate the corrosion inhibition efficiency percentage (% CIE) using the following formula: % CIE = [1 - i(w / inhibitor)(S) / i(w / o inhibitor)(B)] × 100, Where % CIE is the percentage of corrosion inhibition efficiency; i(w / inhibitor)(S) is the current measured at 5000 s for the extract sample at a defined potential; and i(w / o inhibitor)(B) is the current measured at 5000 s for the corresponding blank sample, which consists of 100 mL of phosphate buffer solution.

[0051] Figure 1-3 The evaluation results for the control materials identified above are shown. The regulator was maintained at -0.800 V using the steady-state chronoamperometry method, where the current was measured over time. See also... Figure 3 The procedure used is as follows. calibrated and polished copper, aluminum, and platinum disc working electrodes, with dimensions of 11.3 mm OD × 1.5 mm thickness, were provided. A 150 mL beaker was clamped in place and filled with a 5% NaCl solution and phosphate-buffered saline (SigmaAldrich – P4417-100TAB; 0.137 M, 0.8% NaCl and 0.01 M phosphate buffer, 0.0027 M potassium chloride). The platinum wire reference electrode was rinsed and wiped with deionized water and clamped to one side of the beaker. The regulator working electrode cable was connected to the rotating disc rotator, ensuring that the electrodes did not contact each other in the beaker. The speed was adjusted to 1000 rpm and started. Validation was performed using a blank electrolyte and a solution with a known concentration of corrosion inhibitor.

[0052] This disclosure employs a copper rotating disk electrode. The copper rotating disk electrode enables the observation of oxygen reduction experiments. While not limited to specific theories, the use of a copper rotating disk electrode is considered important for determining the corrosion resistance potential of candidate materials used with aluminum and aluminum alloy substrates, as copper is a key element involved in the kinetics of aluminum corrosion. Previous corrosion analyses using electrodes (e.g., steel electrodes) would not discriminate the appropriate likelihood of corrosion resistance to compounds used with aluminum and aluminum alloy substrates. For example, while potassium phosphate is known to prevent corrosion on aluminum components, known % CIE analytical tests would produce negative results for potassium phosphate due to the use of a steel electrode.

[0053] Thiophenanthrene and 6-amino-2-mercaptobenzothiazole have been reported to provide corrosion inhibition in aluminum alloys (Vukmirovice et al., 2003), as well as DPPH scavenging activity at 1000 ppm (90.69% and 88.42%, respectively). Furthermore, 2,5-dimercapto-1,3,4-thiadiazole is known in the aluminum corrosion literature (it shows poor corrosion inhibition performance in the immersion procedure – ASTM G31-72). However, 2,5-dimercapto-1,3,4-thiadiazole showed good DPPH radical scavenging activity at sample concentrations of 250, 500, and 1000 ppm (74.81%, 83%, and 83.5%, respectively). Butylated hydroxytoluene (BHT) is known as a potent synthetic antioxidant. BHT showed good % DPPH radical scavenging at 250, 500, and 1000 ppm (69%, 85%, and 89%, respectively). Gallic acid, α-tocopherol, and ascorbic acid were used as positive controls in the DPPH antioxidant test. See Table 1, Examples 1A-7B. Table 1 Examples 8-39 Eight (8) species were collected and submitted to the extraction process. Different solvents and solvent mixtures were evaluated, with methanol selected as the optimal solvent. Thirty-seven (37) plant extracts from five (5) different plant species were subjected to DPPH radical scavenging tests. The percentage of DPPH inhibition (%) of the test samples (500 ppm and 1000 ppm) is presented in Table 1 above. The percentage of corrosion inhibition efficiency (% CIE) was then tested by subjecting the plant extract samples to linear sweep voltammetry and chronoamperometry experiments, with the results of %DPPH and %CIE for both plant samples and control samples presented in Table 2 below.

[0054] Thiophenanthrene, 2,5-dimercapto-1,3,4-thiadiazole, 6-amino-2-mercaptobenzothiazole, α-tocopherol (vitamin E), butylated hydroxytoluene, ascorbic acid (vitamin C), and gallic acid were evaluated as known corrosion inhibitors in linear sweep voltammetry and chronoamperometry experiments. Current-change curves are presented in... Figure 1 The applied potential is shown in the figure. A chronoamperometry experiment was conducted while maintaining a potential of -0.953 V, and the results are shown in... Figure 2 In the middle. For the inhibitor at a concentration of 1000 ppm, the current density (A / cm²) 2 The graph was plotted as a function of the applied potential (V). The results showed that, except for thiophenol, no plateau was observed for the tested inhibitors at a potential of -0.953 V.

[0055] The potential was changed and an anode scan curve was obtained using a potential maintained at -0.70 V (see [reference]). Figure 3 When some compounds were observed to have a plateau close to -0.60 V, new experiments were conducted while maintaining a potential of -0.60 V.

[0056] The seeds, pulp, and peel of *Annona squamosa* and *Annona squamosa* fruits were separated, frozen, and freeze-dried. The seeds were ground in a pre-cooled mortar and pestle under liquid nitrogen. The frozen powder was transferred to tubes and freeze-dried for two days. The weighed material was continuously extracted by immersion in hexane and ethanol (70% v / v) under ultrasonic treatment for 20 minutes. Immersion is understood as a process by which solids are softened or separated into constituent parts by soaking in a liquid—such as a solvent. The seed / solvent ratio was 1:3 (w / v). The solvent was removed using a rotary evaporator under reduced pressure (700 mm Hg, vacuum pump). The resulting hexane extract was obtained as a pale yellow oil, yielding 31.5% dry weight. The ethanol extract was obtained as a brown slurry, yielding 14% dry weight. The peel of *Annona squamosa* and *Annona squamosa* fruits, after grinding and freeze-drying, was extracted by immersion in 75% ethanol under ultrasonic treatment for 20 minutes. The peel / solvent ratio was 1:3 (w / v). The solvent was removed using a rotary evaporator under reduced pressure (700 mm Hg, vacuum pump). The resulting thick-petaled custard apple peel extract was obtained as a dark slurry, yielding 22.4% dry weight. The resulting custard apple peel extract was also obtained as a dark slurry, yielding 20.2% dry weight.

[0057] Leaves of a species of *Incainca* were ground in liquid nitrogen using a pre-cooled mortar and pestle. The frozen powder was transferred to tubes and freeze-dried for two days. The weighed material was extracted with methanol (MeOH) under sonication for 20 minutes. After solvent removal under reduced pressure, the methanol extract of the leaves was obtained. The leaf extract was maintained at 4ºC in the dark.

[0058] The obtained extracts were screened using a DPPH free radical scavenger assay. Antioxidant activity was tested in 96-well microplates using five different concentrations of each substance (500, 250, 125, 62.5, and 31.25 µg / mL) (Erkan, Cetin., Ayranci. 2011; Roesler, Catharino, Malta, Eberlin, & Pastore, 2007). DPPH MeOH solution (250 µL) was added 0.004% (w / v) to the MeOH solution (10 µL) of the compound to be tested. The absorbance was measured at 492 nm after 30 min. A control was prepared as above but without any extract, and methanol was used for baseline correction. Radical scavenging was expressed as a percentage of inhibition and calculated using the following formula: %suppression= [(A DPPH – A ext ) / A DPPH 100 Where ADPPH is the absorbance value of the blank sample for DPPH and AExt is the absorbance value of the test solution. AExt is evaluated as the difference between the absorbance value of the test solution and that of its blank. Report the % IC values ​​for the dry extract and isolated compounds at a final concentration of 500 µg / mL.

[0059] Those skilled in the art will understand that the accepted “abbreviated” list of various plant species lists the genera in an abbreviated manner, such as *Annona squamosa* (thick-petaled custard apple). A. crassiflora ) is thick-petaled custard apple ( Annona crassiflora Equivalent terms, etc. Furthermore, EtOH is the equivalent chemical abbreviation for ethanol, and MeOH is the equivalent chemical abbreviation for methanol. Extracts were obtained in 10 g amounts from each of the following five (5) plants: 1 – Sourdoughnut (Annona squamosa) – Seed Extract 2 – Soursop – Peel Extract 3 – Leaf extracts from certain species of the genus *Inca Inca* 4 – Mango – Leaf Extract 5 – Custard Apple – Peel Extract The following three (3) plant extracts showed good DPPH radical scavenging activity at 1000 ppm (where "good" DPPH assay is understood as DPPH radical scavenging activity >85%): Bidens trifoliata, Annona squamosa, and Annuus custardii. Bidens trifoliata leaves and branches were extracted with methanol, and the methanol extract showed 85.05% antioxidant activity at 1000 ppm. The fruit of Annuus custardii was separated into seeds, pulp, and peel and extracted with methanol, and the antioxidant activities presented in Tables 1 and 2 are shown.

[0060] The best-performing plant extracts are those with the following results: 1) high DPPH free radical scavenging test results (greater than approximately 80%) and 2) high % CIE percentage. These results are listed in Table 2 below, along with the performance of several control compounds (for comparison) known to have the necessary levels of corrosion inhibition [thiophenol, 2,5-dimercapto-1,3,4-thiadiazole, 6-amino-2-mercaptobenzothiazole, α-tocopherol (vitamin E), butylated hydroxytoluene (BHT), ascorbic acid (vitamin C), and gallic acid].

[0061] Table 2 As shown in Table 2, the plant extracts of Bidens trifoliata, Annona squamosa peel, and Annona squamosa thick-petaled peel all produced %DPPH and %CIE values ​​exceeding 80% at a concentration of 1000 ppm.

[0062] Figure 4 This is a graph showing the polarization curves (anodic scans) of the plant extract tested at a concentration of 1000 ppm against a control compound sample—which is known to possess antioxidant properties—over a period of 5000 s at -0.60 V. Figure 5 It displays the current density (A / cm²). 2 The graph is plotted as a function of the applied potential (V) for control compound samples known to have antioxidant properties at a concentration of 1000 ppm and plant extracts at a concentration of 1000 ppm. Figure 6 This is a graph showing the correlation between the % DPPH free radical scavenging test of plant extract samples as a function of % corrosion inhibition efficiency (% CIE).

[0063] The extract samples shown in Table 3 below were dissolved in methanol at concentrations of 5% and 20% and incorporated into the primer formulation as follows: 8 parts Duxone DXPU polyurethane; 1 part Duxone DX700 catalyst. Duxone DX 700 solvent diluent was also added. (Duxone products are manufactured by DuPont). Solids were removed by filtration through a sieve. The primer, including the sol-gel (DesogelEAP-9 (Gol Airlines)), was used to coat aluminum 2024 T3 plates. The plates were then coated using the extract formulation by painting. For reference, a formulation of Vanlube 829 (RT Vanderbilt Co.) at a 20% concentration was also prepared. Aluminum 2024 T3 plates were coated using Vanlube 829 by painting. The plates were then prepared for scratch testing according to ASTM D7091-13. After 336 hours of salt spray testing (ASTM B117), aluminum plates coated with extract / primer formulations—containing extracts of custard apple peel and mango leaf—visually and upon scanning electron microscopy (SEM) showed protection against corrosion to a degree substantially similar to that of plates coated with Vanlube 829. Mango extract samples were obtained using the methods and protocols described herein for obtaining other plant extract samples. Table 3 below shows the results of the 5% salt spray test on plates treated with the scratch test ASTM 1654. Each of the tested and reported extracts in Table 3 above represents more than 85% corrosion inhibition efficiency.

[0064] Table 3 Salt spray corrosion test matrix and results Figure 7-10 is a flowchart summarizing aspects of this disclosure. According to one aspect of this disclosure, Figure 7 A predictive method 70 for selecting plant extracts that have the required level of corrosion inhibition for aluminum and aluminum alloys is summarized, comprising performing a diphenylpicrylhydrazone (DPPH) radical scavenging test on a plant extract sample 71, obtaining a DPPH radical scavenging corrosion inhibition value for the plant extract sample 72, obtaining a percentage of corrosion inhibition efficiency for the plant extract sample 73, comparing the DPPH radical scavenging value with the percentage of corrosion inhibition efficiency for the plant extract sample 74, and selecting plant extracts exhibiting both a DPPH radical scavenging value greater than approximately 80% and a corrosion inhibition efficiency greater than approximately 80% for use in corrosion-inhibiting coatings for the substrate material 75.

[0065] According to further aspects of this disclosure, Figure 8 A predictive method 80 for selecting plant extracts with the required level of corrosion inhibition for aluminum and aluminum alloys is summarized, comprising: performing a diphenylpicrylhydrazone (DPPH) radical scavenging test on plant extract samples 81; obtaining the DPPH radical scavenging corrosion inhibition value of the plant extract samples 82; performing a linear sweep voltammetry test on the plant extract samples 86; obtaining the percentage of corrosion inhibition efficiency for each of a plurality of plant extract samples 83; comparing the DPPH radical scavenging test value of the plant extract samples with the percentage of corrosion inhibition efficiency of the plant extract samples 84; and selecting plant extracts exhibiting both a DPPH radical scavenging test value greater than approximately 80% and a corrosion inhibition efficiency greater than approximately 80% for corrosion-inhibiting coatings 85. Figure 7 The aspects shown in the middle can be incorporated into Figure 8 The method shown in the text.

[0066] According to another aspect of this disclosure, Figure 9 A predictive method 90 for selecting plant extracts with the required level of corrosion inhibition for aluminum and aluminum alloys is summarized, comprising: extracting multiple plant extract samples 91; performing a diphenylpicrylhydrazone (DPPH) radical scavenging test on the plant extract samples 81; obtaining the DPPH radical scavenging corrosion inhibition value of the plant extract samples 82; performing a linear sweep voltammetry test on the plant extract samples 86; obtaining the percentage of corrosion inhibition efficiency of the plant extract samples 83; comparing the DPPH radical scavenging test value with the percentage of corrosion inhibition efficiency of the plant extract samples 84; and selecting plant extracts exhibiting both a DPPH radical scavenging test value greater than approximately 80% and a corrosion inhibition efficiency greater than approximately 80% for corrosion-inhibiting coatings 85. Figure 7-8 The aspects shown in the middle can be incorporated into Figure 9 The method shown in the text.

[0067] According to another aspect of this disclosure, Figure 10A predictive method 100 for selecting plant extracts with the required level of corrosion inhibition for aluminum and aluminum alloys is summarized, comprising: treating a sample of plant seeds, plant pulp, plant peel, or a combination thereof to obtain a sample 101; adding a solvent to the sample 102; obtaining an extract 103 from the solvent; performing a diphenylpicrylhydrazone (DPPH) radical scavenging test 81 on the plant extract sample; obtaining a DPPH radical scavenging corrosion inhibition value 82 for the plant extract sample; performing a linear sweep voltammetry test 86 on multiple plant extract samples; obtaining a percentage corrosion inhibition efficiency 83 for the plant extract sample; comparing the DPPH radical scavenging test value with the percentage corrosion inhibition efficiency 84 for the plant extract sample; and selecting plant extracts exhibiting both a DPPH radical scavenging test value greater than approximately 80% and a corrosion inhibition efficiency greater than approximately 80% for corrosion-inhibiting coatings 85. Figure 7-9 The aspects shown in the middle can be incorporated into Figure 10 The method shown in the text.

[0068] Figure 11 This is a flowchart illustrating aspects of the present disclosure, thereby presenting a method 110 for inhibiting corrosion, which includes applying a composition 112 comprising plant extracts to a substrate and inhibiting corrosion of the substrate 114.

[0069] Variations and alternatives to this disclosure relate to the manufacture and coating of various aluminum, aluminum alloy, copper, and copper alloy substrates, which, in a non-limiting sense, include a variety of components and parts, such as, for example, components and parts of any size, including components and parts manufactured and used for making larger parts and structures. Such components and parts include, but are not limited to, components and parts designed to be mounted on the exterior or interior of stationary objects, which, in a non-limiting sense, include bridge trusses, support columns, general structural objects, buildings, etc. Further components and parts, in a non-limiting sense, include components and parts for manufacturing non-stationary objects, which, in a non-limiting sense, include all types of transportation, including atmospheric and air transport vehicles and other objects, and structures designed for space or other upper atmospheric environments, such as, for example, manned or unmanned vehicles and objects. The objects under consideration include, but are not limited to, vehicles, such as, for example, aircraft, spacecraft, satellites, rockets, missiles, etc., and therefore include manned and unmanned aircraft, manned and unmanned spacecraft, manned and unmanned land vehicles, manned and unmanned non-land vehicles, and even manned and unmanned water vehicles and manned and unmanned underwater vehicles and objects.

[0070] Further aspects are described in the following clauses: Clause 1. A method for inhibiting corrosion of a substrate, comprising: Apply the composition to the substrate, the composition comprising a plant genus including: Annonaceae. ， Inca Beans ， Extracts of the genera *Mangifera*, *Taraxacum*, *Bidens*, *Plantago*, *Matricaria*, *Solidago*, and combinations thereof; and Inhibit corrosion of the substrate, the substrate including the substrate surface.

[0071] Clause 2. The method of Clause 1, wherein, in the step of applying the composition to the substrate, the composition comprises an extract derived from plant species including: custard apple; *Inca inca* (a certain species); mango; custard apple; dandelion; beggar-ticks; plantain; magnolia; goldenrod; and combinations thereof.

[0072] Clause 3. The method of Clause 1 or 2, wherein in the step of applying the composition to the substrate, the composition comprises an extract derived from plant species including: custard apple, custard apple, mango, beggar-ticks, and combinations thereof.

[0073] Clause 4. The method of any one of Clauses 1-3, wherein in the step of applying the composition to the substrate, the composition comprises an extract derived from a plant species including: custard apple; custard apple; mango; Bidens trifoliata; and combinations thereof, and said extract is present in said composition at a concentration ranging from about 5% to about 20%.

[0074] Clause 5. The method of any one of Clauses 1-4, wherein in the step of applying the composition to the substrate, the substrate comprises aluminum, aluminum alloy, copper, copper alloy, and combinations thereof.

[0075] Clause 6. The method of any one of Clauses 1-5, wherein, in the step of applying the composition to the substrate, the substrate comprises aluminum alloy 2024 T3 or aluminum alloy 7075.

[0076] Clause 7. A composition for inhibiting corrosion on a substrate, said composition comprising: Extracts derived from genera including: Annuae, Inca Inca, Mango; Taraxacum; Bidens; Plantago; Matricaria; Solidago; and combinations thereof.

[0077] Clause 8. The composition of Clause 7, wherein the composition comprises an extract derived from plant species including: custard apple; *Inca Inca* (a certain species); mango; custard apple; dandelion; beggar-ticks; plantain; magnolia; goldenrod; and combinations thereof.

[0078] Clause 9. The composition of Clause 7 or 8, wherein the composition comprises an extract derived from plant species including: custard apple; custard apple; mango; Bidens trifoliata; and combinations thereof.

[0079] Clause 10. A composition of any one of Clauses 7-9, wherein the composition comprises an extract derived from a plant species including: custard apple; custard apple; mango; Bidens trifoliata; and combinations thereof, and said extract is present in said composition at a concentration ranging from about 5% to about 20%.

[0080] Clause 11. A composition of any one of Clauses 7-10, wherein the extract derived from a plant genus is extracted from plant seeds, plant pulp, plant bark, plant leaves, and combinations thereof.

[0081] Clause 12. A composition of any one of Clauses 7-11, wherein the composition further comprises a primer.

[0082] Clause 13. The composition of Clause 12, wherein the primer comprises a polyurethane compound.

[0083] Clause 14. The composition of Clause 12, wherein the composition is used as an additive in a coating formulation.

[0084] Clause 15. A coating for inhibiting corrosion, said coating comprising: Extracts derived from genera including: Annuae, Inca Inca, Mango; Taraxacum; Bidens; Plantago; Matricaria; Solidago; and combinations thereof.

[0085] Clause 16. The coating of Clause 15, wherein the coating comprises extracts derived from plant species including: custard apple; *Inca Inca* (a certain species); mango; custard apple; *Bidens trifoliata*; and combinations thereof.

[0086] Clause 17. A base comprising a compound for inhibiting corrosion, said compound comprising: Extracts derived from genera including: Annuae, Inca Inca, Mango; Taraxacum; Bidens; Plantago; Matricaria; Solidago; and combinations thereof.

[0087] Clause 18. The base of Clause 17, wherein the compounds include extracts derived from plant species including: custard apple; *Inca inca* (a certain species); mango; custard apple; *Bidens trifoliata*; and combinations thereof.

[0088] Clause 19. The substrate of Clause 17 or 18, wherein the substrate comprises aluminum, aluminum alloys, copper, copper alloys, and combinations thereof.

[0089] Clause 20. The substrate of any one of Clauses 17-19, wherein the substrate comprises aluminum alloy 2024 T3, aluminum alloy 7075, and combinations thereof.

[0090] When describing elements of this disclosure or exemplary aspects thereof, the articles “a,” “an,” “the,” and “the” are intended to mean the presence of one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that additional elements may be present in addition to those listed. While this disclosure has been described with respect to specific aspects, the details of those aspects are not to be construed as limiting. While preferred variations and alternatives to this disclosure have been described and illustrated, it will be appreciated that various changes and substitutions may be made therein without departing from the spirit and scope of this disclosure.

Claims

1. A method for inhibiting corrosion of a substrate, comprising: Apply a composition to a substrate, the composition comprising extracts derived from plant genera including: *Annona squamosa*, *Inca indica*, *Mangifera*; *Taraxacum*; *Bidens*; *Plantago*; *Matricaria*; *Solidago canadensis*; and combinations thereof; and Suppress corrosion of the substrate, the substrate including a substrate surface.

2. The method of claim 1, wherein, In the step of applying the composition to the substrate, the composition comprises an extract derived from a plant species, including: custard apple; *Inca Inca* (a certain species); mango; custard apple; dandelion; beggar-ticks; plantain; matricaria; goldenrod; and combinations thereof.

3. The method of claim 1 or 2, wherein in the step of applying the composition to the substrate, the composition comprises an extract derived from a plant species, said plant species including: Thick-petaled custard apple; cherimoya; Mango; Bidens trifoliata; And its combination.

4. The method of any one of claims 1-3, wherein in the step of applying the composition to the substrate, the composition comprises an extract derived from a plant species, said plant species comprising: Thick-petaled custard apple; cherimoya; Mango; Bidens trifoliata; And in combination thereof, and the extract is present in the composition at a concentration ranging from about 5% to about 20%; or In the step of applying the composition to the substrate, the substrate comprises aluminum alloy 2024 T3 or aluminum alloy 7075.

5. A composition for inhibiting corrosion on a substrate, said composition comprising: Extracts derived from genera including: Annuae, Inca Inca, Mango; Taraxacum; Bidens; Plantago; Matricaria; Solidago; and combinations thereof.

6. The composition of claim 5, wherein the composition comprises an extract derived from a plant species, said plant species including: Thick-petaled custard apple; *Inca Inca* (a species); mango; custard apple; dandelion; Bidens trifoliata; long-leaved plantain; Matricaria; Chilean goldenrod; and their combinations.

7. The composition of claim 5 or 6, wherein the composition comprises an extract derived from a plant species, said plant species including: Thick-petaled custard apple; custard apple; mango; Bidens trifoliata; And its combination.

8. The composition of any one of claims 5-7, wherein the composition comprises an extract derived from a plant species, said plant species including: Thick-petaled custard apple; custard apple; mango; Bidens trifoliata; And in combination therewith, and the extract is present in the composition at a concentration ranging from about 5% to about 20%.

9. The composition of any one of claims 5-8, wherein the composition further comprises a primer.

10. The composition of claim 9, wherein the primer comprises a polyurethane compound.

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