Composition and method for inhibiting metal corrosion against acid

Abstract

A method for inhibiting corrosion of a metal article includes contacting the metal article with a corrosive medium containing an acid and a zinc phthalocyanine (Zn-Pc) compound thereby adsorbing the Zn-Pc compound onto at least one surface of the metal article. The Zn-Pc compound is present in the corrosive medium in an amount of 0.01 to 1 millimoles per liter (mmol / L). The Zn-Pc compound is of formula (I).

Description

BACKGROUNDTechnical Field

[0001] The present disclosure is directed to zinc phthalocyanine (Zn-Pc) compounds, compositions containing zinc phthalocyanine (Zn-Pc) compounds, and more particularly to methods for inhibiting corrosion of a metal article in a corrosive medium in the presence of a zinc phthalocyanine (Zn-Pc) compound.Description of Related Art

[0002] The “background” description provided herein is to present the context of the disclosure generally. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.

[0003] Metal surfaces are prone to corrosion, which may cause safety and financial challenges for industries utilizing such metals in infrastructure. Nitrogen-based heterocycles have been evaluated as corrosion inhibitors (See: Verma et al. J. Mol. Liquids 334 (2021) 116441). Many of these compounds exhibit their inhibitory mechanism through physiochemisorption mode. It is recognized that the inhibitory potential of heterocyclic compounds depends on various factors such as concentration, temperature, substitutions, nature of metal, exposure time, and availability of salts. Phthalocyanins are heterocyclic compounds that may form complexes with metallic atoms through non-bonding and π-electrons.

[0004] CN108977813B discloses an inhibitor composition containing a zinc phthalocyanine (Zn-Pc) compound. However, CN108977813B does not describe a Zn-Pc compound having a ball-type geometry.

[0005] CN106280886B discloses a graphene-oxide modified Zn-Pc compound. The graphene-oxide modified Zn-Pc compound may be a tetra-nitro zinc phthalocyanine loaded with graphene-oxide. However, CN106280886B does not describe a Zn-Pc compound having a ball-type geometry.

[0006] Khan et al. (See: Surf. Eng. Appl. Electrochem., 2023) discloses an amide substituted Zn-Pc compound. The amide substituted Zn-Pc compound may be a tetra-nitro zinc phthalocyanine. However, Khan does not describe a Zn-Pc compound having a ball-type geometry.

[0007] Samal et al. (See: Colloids Surf. A Physicochem. Eng. Asp., 2022) discloses an inhibitor composition containing a zinc phthalocyanine (Zn-Pc) compound, and a method for inhibiting corrosion of a copper article. However, Samal does not describe a Zn-Pc compound having a ball-type geometry, or a method for inhibiting corrosion of a metal article made from aluminium.

[0008] Bilgiçli et al. (See: J. Photochem. Photobiol., A., 2019) discloses a ball-type zinc phthalocyanine (Zn-Pc) compound. The Zn-Pc compound contains a 4,4′-disulfanediyldiphthalonitrile motif. However, Bilgiçli does not describe a Zn-Pc compound a method for inhibiting corrosion of a aluminium metal article.

[0009] The utilization of phthalocyanins for anti-corrosive applications in the industry is limited by their insolubility in aqueous-based electrolytes when in a pure form. Although a few phthalocyanine-based anti-corrosive materials have been used, each of them suffers from one or more drawbacks hindering their effective adoption for corrosion inhibition in acidic media. Hence, there is a need to develop a corrosion inhibitor that may overcome or reduce the limitations above.

[0010] In view of the foregoing, it is one objective of the present disclosure to provide a method for inhibiting corrosion of a metal article in a corrosive medium. A second objective of the present disclosure is to provide a method of preparing a zinc phthalocyanine (Zn-Pc) compound.SUMMARY

[0011] In an exemplary embodiment, a method for inhibiting corrosion of a metal article in contact with a corrosive medium is described. The method includes contacting the metal article with the corrosive medium comprising an acid and a zinc phthalocyanine (Zn-Pc) compound thereby adsorbing the Zn-Pc compound onto at least one surface of the metal article. In some embodiments, the Zn-Pc compound is present in the corrosive medium in an amount of 0.01 to 1 millimoles per liter (mmol / L). In some embodiments, the Zn-Pc compound has a formula (I)

[0012] In some embodiments, R1, R2, and R3 are each independently selected from the group consisting of a hydrogen atom, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, an amine group, a nitro group, and a cyano group.

[0013] In some embodiments, the metal article is made of Aluminium.

[0014] In some embodiments, at least one surface of the metal article is made of aluminium.

[0015] In some embodiments, the metal article is part of a casing, a pipe, a pump, a screen, a valve, or a fitting of an oil or a gas well.

[0016] In some embodiments, the acid is at least one selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), acetic acid, and hydrofluoric acid (HF).

[0017] In some embodiments, the contacting the metal article with the corrosive medium is at a temperature of 290 to 340 Kelvin (K).

[0018] In some embodiments, the metal article has a corrosion rate of about 50 to 500 millimeter penetration per year (mmpy). In some embodiments, the at least one surface of the metal article is in contact with the corrosive medium at 298 to 333 K. In some embodiments, the Zn-Pc compound is present in the corrosive medium in an amount from 0.01 to 0.4 mmol / L.

[0019] In some embodiments, introducing the Zn-Pc compound provides an inhibition efficiency of 10 to 75% when the at least one surface of the metal article is in contact with the corrosive medium at 298 to 333 K. In some embodiments, the Zn-Pc compound is present in the corrosive medium in an amount from 0.01 to 0.4 mmol / L.

[0020] In some embodiments, the metal article is made of aluminium. In some embodiments, the metal article has an activation energy of 6 to 14 kilojoules per mole (KJ / mole) when the metal article is in contact with the corrosive medium at 298 to 333 K. In some embodiments, the Zn-Pc compound is present in the corrosive medium in an amount from 0.01 to 0.4 mmol / L.

[0021] In some embodiments, the Zn-Pc has a ball-type geometry.

[0022] In some embodiments, the Zn-Pc compound has a formula (II)

[0023] In some embodiments, the Zn-Pc compound absorbed onto at least one surface of the metal article is present in the form of a film.

[0024] In some embodiments, at least 70% of the one surface of the metal article is covered by a film of the Zn-Pc compound, each % based on a total surface area of at least one surface of the metal article.

[0025] In some embodiments, the at least one surface of the metal article is made of aluminium. In some embodiments, the at least one surface has a smoother surface morphology compared to a same surface of the metal article in contact with the corrosive medium in the absence of the Zn-Pc compound.

[0026] In some embodiments, the at least one surface of the metal article comprises about 0.1 to 1 wt. % carbon, about 0.1 to 1 wt. % nitrogen, about 1 to 4 wt. % oxygen, about 0.1 to 1 wt. % zinc, and about 90 to 99.9 wt. % aluminum, each wt. % based on a total weight of the metal article, as determined by Energy Dispersive X-ray Spectroscopy (EDS).

[0027] In some embodiments, the at least one surface of the metal article comprises about 0.53 wt. % carbon, about 0.36 wt. % nitrogen, about 2.19 wt. % oxygen, about 0.52 wt. % zinc, and about 96.41 wt. % aluminum, each wt. % based on the total weight of the metal article, as determined by EDS.

[0028] In an exemplary embodiment, a method of preparing the Zn-Pc compound is described. The method includes mixing and heating a nitrophthalonitrile of Formula (III), a biphenol of formula (IV) and DMSO in the presence of a base to form a precursor. The method of preparing the Zn-Pc compound further includes heating the precursor and zinc (II) acetate to form a mixture, and washing.

[0029] In some embodiments, R1, R2, and R3 are each independently selected from the group consisting of a hydrogen atom, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, an amine group, a nitro group, and a cyano group.

[0030] In some embodiments, the nitrophthalonitrile is 3-nitrophthalonitrile.

[0031] In some embodiments, the biphenol is 4,4′-dihydroxybiphenyl.

[0032] In some embodiments, the base comprises sodium carbonate, and potassium carbonate.

[0033] The foregoing general description of the illustrative present disclosure and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure and are not restrictive.BRIEF DESCRIPTION OF THE DRAWINGS

[0034] A more complete appreciation of this disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0035] FIG. 1A is a flow chart depicting a method for inhibiting corrosion of a metal article in contact with a corrosive medium, according to certain embodiments;

[0036] FIG. 1B is a flow chart depicting a method of preparing a Zn-Pc compound, according to certain embodiments;

[0037] FIG. 1C is a schematic illustration depicting the synthesis of a ball-type phthalocyanine, according to certain embodiments;

[0038] FIG. 2A shows Fourier-Transform Infrared (FTIR) spectra of compound 3, according to certain embodiments;

[0039] FIG. 2B shows FTIR spectra of Zn-Pc ball-type, compound 4 of formula (II), according to certain embodiments;

[0040] FIG. 3 shows ultraviolet (UV) visible (UV-Vis) light spectra of compound 4 of formula (II), according to certain embodiments;

[0041] FIG. 4 shows photoluminescence spectra of compound 4 of formula (II), according to certain embodiments;

[0042] FIG. 5 shows a Langmuir isotherm plot for Zn-Pc corrosion inhibition of aluminium in 1 M HCl at 293 K, according to certain embodiments;

[0043] FIG. 6A shows an Arrhenius plot for corrosion of aluminum in 1 M HCl with and without Zn-Pc (0.01-0.4 mmol / L), according to certain embodiments;

[0044] FIG. 6B shows transition state plots for corrosion of aluminum in 1 M HCl with and without Zn-Pc (0.01-0.4 mmol / L), according to certain embodiments;

[0045] FIG. 7A shows a scanning electron micrograph (SEM) micrograph of a freshly polished aluminum specimen at 20 μm magnification, according to certain embodiments;

[0046] FIG. 7B shows an SEM micrograph of aluminum specimen immersed in the absence of ball-type Zn-Pc at 20 μm magnification, according to certain embodiments;

[0047] FIG. 7C shows an SEM micrograph of aluminum specimen immersed in the presence of ball-type Zn-Pc at 20 μm magnification in 1.0 M HCl, according to certain embodiments;

[0048] FIG. 7D shows an SEM micrograph of freshly polished aluminum specimen at 50 μm magnification, according to certain embodiments;

[0049] FIG. 7E shows an SEM micrograph of aluminum specimen immersed in the absence of ball-type Zn-Pc at 50 μm magnification, according to certain embodiments;

[0050] FIG. 7F shows an SEM micrograph of Al specimen immersed in the presence of ball-type Zn-Pc at 50 μm magnification in 1.0 M HCl, according to certain embodiments;

[0051] FIG. 8A shows energy-dispersive X-ray spectrum (EDS) of aluminum specimen immersed in the absence of ball-type Zn-Pc, according to certain embodiments;

[0052] FIG. 8B shows EDS spectrum of aluminum specimen immersed in presence of ball-type Zn-Pc in 1.0 M HCl, according to certain embodiments;

[0053] FIG. 9A shows the structural geometry, highest occupied molecular orbital (HOMO)-least unoccupied molecular orbital (LUMO) frontier orbital distribution, and the electrostatic potential (ESP) map of of Zn-Pc, according to certain embodiments;

[0054] FIG. 9B shows the structural geometry, HOMO-LUMO frontier orbital distribution, and the electrostatic potential (ESP) map of H+—Zn-Pc, according to certain embodiments;

[0055] FIG. 10 shows the electronic properties of Zn-Pc and H+—Zn-Pc in an aqueous medium at the B3LYP / 6-31G* & SDD levels of theory, according to certain embodiments;

[0056] FIG. 11 depicts hydrogen nuclear magnetic resonance (1H NMR) spectra of the compound (3) in FIG. 1C, according to certain embodiments;

[0057] FIG. 12 depicts carbon nuclear magnetic resonance (13C NMR) spectra of the compound (3) in FIG. 1C, according to certain embodiments; and

[0058] FIG. 13 depicts hydrogen nuclear magnetic resonance (1H NMR) spectra of the compound (4) in FIG. 1C, according to certain embodiments.DETAILED DESCRIPTION

[0059] When describing the present disclosure, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0060] Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings wherever applicable, in that some, but not all embodiments of the disclosure are shown.

[0061] In the drawings, like reference numerals designate identical or corresponding parts throughout the several views. Further, as used herein, the words “a,”“an” and the like generally carry a meaning of “one or more,” unless stated otherwise.

[0062] As used herein, the words “about,”“approximately,” or “substantially similar” may be used when describing magnitude and / or position to indicate that the value and / or position described is within a reasonable expected range of values and / or positions. For example, a numeric value may have a value that is + / −0.1% of the stated value (or range of values), + / −1% of the stated value (or range of values), + / −2% of the stated value (or range of values), + / −5% of the stated value (or range of values), + / −10% of the stated value (or range of values), + / −15% of the stated value (or range of values), or + / −20% of the stated value (or range of values). Within the description of this disclosure, where a numerical limit or range is stated, the endpoints are included unless stated otherwise. Also, all values and subranges within a numerical limit or range are specifically included as if explicitly written out.

[0063] The use of the terms “include,”“includes”, “including,”“have,”“has,” or “having” should be generally understood as open-ended and non-limiting unless specifically stated otherwise.

[0064] As used herein, the term “compound” generally refers to a variety of chemicals composed of one or more chemical elements, whether as a solid, liquid, or gas, and whether in a crude mixture or isolated and purified.

[0065] As used herein, the term “corrosion” generally refers to that material decomposes because chemical reaction occurs with its surrounding environment. There are two main types of corrosion: general or uniform attack corrosion and galvanic corrosion. Typical or uniform corrosion happens, for instance, when the iron is in a humid environment, creating iron oxide and corroding.

[0066] As used herein, a “corrosive medium” is a material that attacks and damages the surface it encounters.

[0067] As used herein, the term “corrosion inhibitor” generally refers to the chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy, that meets the fluid. The effectiveness of a corrosion inhibitor may depend on fluid composition, quantity of water, and flow regime.

[0068] As used herein, the term “alkyl” unless otherwise specified refers to both branched and straight chain saturated aliphatic primary, secondary, and / or tertiary hydrocarbons of typically C1 to C20, preferably C6-C18, more preferably C10-C16, for example C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, and specifically includes, but is not limited to, methyl, trifluoromethyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, t-butyl, pentyl, cyclopentyl, isopentyl, neopentyl, hexyl, isohexyl, cyclohexyl, cyclohexylmethyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 2-ethylhexyl, heptyl, octyl, nonyl, 3,7-dimethyloctyl, decyl, undecyl, dodecyl, tridecyl, 2-propylheptyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl. As used herein, the term optionally includes substituted alkyl groups. Exemplary moieties with which the alkyl group can be substituted may be selected from the group including, but not limited to, hydroxyl, amino, alkylamino, arylamino, alkoxy, aryloxy, nitro, cyano, sulfonic acid, sulfate, phosphonic acid, phosphate, halo, or phosphonate or mixtures thereof. The substituted moiety may be either protected or unprotected as necessary, as known to those skilled in the art. As used herein, the term “cycloalkyl” refers to a non-aromatic ring that is fully hydrogenated having one, two or three rings wherein such rings may be condensed. Cycloalkyl also includes bicyclic structures that may be bridged or spirocyclic in nature with each individual ring within the bicycle varying from 3-8 atoms. Exemplary cyclic hydrocarbon (i.e. cycloalkyl) groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, norbornyl, and adamantyl. Branched cycloalkyl groups, such as exemplary 1-methylcyclopropyl and 2-methylcyclopropyl groups, are included in the definition of cycloalkyl as used in the present disclosure.

[0069] As used herein, the term “substituted” refers to at least one hydrogen atom that is replaced with a non-hydrogen group, provided that normal valencies are maintained and that the substitution results in a stable compound. When a compound or a R group (denoted as R1, R2, and so forth) is noted as “optionally substituted”, the substituents are selected from the exemplary group including, but not limited to, aroyl (as defined hereinafter), halogen (e.g. chlorine, bromine, fluorine or iodine), alkoxy (i.e. straight or branched chain alkoxy having 1 to 10 carbon atoms, and includes, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, secondary butoxy, tertiary butoxy, pentoxy, isopentoxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, and decyloxy), cycloalkyloxy including cyclopentyloxy, cyclohexyloxy, and cycloheptyloxy, aryloxy including phenoxy and phenoxy substituted with halo, alkyl, alkoxy, and haloalkyl (which refers to straight or branched chain alkyl having 1 to 8 carbon atoms which are substituted by at least one halogen, and includes, for example, chloromethyl, bromomethyl, fluoromethyl, iodomethyl, 2-chloroethyl, 2-bromoethyl, 2-fluoroethyl, 3-chloropropyl, 3-bromopropyl, 3-fluoropropyl, 4-chlorobutyl, 4-fluorobutyl, dichloromethyl, dibromomethyl, difluoromethyl, diiodomethyl, 2,2-dichloroethyl, 2,2-dibromoethyl, 2,2-difluoroethyl, 3,3-dichloropropyl, 3,3-difluoropropyl, 4,4-dichlorobutyl, 4,4-difluorobutyl, trichloromethyl, trifluoromethyl, 2,2,2-tri-fluoroethyl, 2,3,3-trifluoropropyl, 1,1,2,2-tetrafluoroethyl, 2,2,3,3-tetrafluoropropyl), hydrocarbyl, arylalkyl, hydroxy, alkoxy, oxo, alkanoyl, alkanoyloxy, amino, alkylamino, arylamino, arylalkylamino, disubstituted amines (e.g. in which the two amino substituents are selected from the exemplary group including, but not limited to, alkyl, aryl, or arylalkyl), alkanylamino, arylamino, alkanoylamino, thiol, alkylthio, arylthio, arylalkylthio, alkylthiono, arylthiono, aryalkylthiono, alkylsulfonyl, arylsulfonyl, arylalkylsulfonyl, sulfonamido (e.g. —SO2NH2), substituted sulfonamide, nitro, cyano, carboxy, carbamyl (e.g. —CONH2, —CONHalkyl, —CONHaryl, —CONHarylalkyl or cases where there are two substituents on one nitrogen from alkyl, aryl, or arylalkyl), alkoxycarbonyl, aryl, guanidine, heteroarylcarbonyl, heterocyclyl, and mixtures thereof and the like. The substituents may be either unprotected, or protected as necessary, as known to those skilled in the art, for example, as taught in Greene, et al., “Protective Groups in Organic Synthesis”, John Wiley and Sons, Second Edition, 1991, hereby incorporated by reference in its entirety).

[0070] As used herein, the term “optionally” generally refers to includes substituted alkyl groups. The examples include, but are not limited to, hydroxy, amino, alkylamino, arylamino, alkoxy, aryloxy, nitro, cyano, sulfonic acid, sulfate, phosphonic acid, phosphate, halo, or phosphonate or mixtures thereof. The substituted moiety may be either protected or unprotected as necessary, as known to those skilled in the art.

[0071] As used herein, the term “cycloalkyl” generally refers to cyclized alkyl groups. Suitable examples of cycloalkyl groups include but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, norbornyl, and adamantly, 1-methylcyclopropyl and 2-methylcyclopropyl.

[0072] As used herein, the term “alkoxy” generally refers to a straight or branched chain alkoxy including, but not limited to, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, secondary butoxy, tertiary butoxy, pentoxy, isopentoxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, and decyloxy.

[0073] As used herein, the term “aryl” unless otherwise specified generally refers to functional groups or substituents derived from an aromatic ring including, but not limited to, phenyl, biphenyl, napthyl, thienyl, and indolyl.

[0074] As used herein, the term “halogen” generally refers to fluorine, chlorine, bromine and iodine.

[0075] Unless otherwise noted, the present disclosure is intended to include all isotopes of a given compound or formula.

[0076] As used herein, “inhibition efficiency” is a measure of effectiveness in inhibiting the corrosion of the metal article when in contact with the corrosive medium.

[0077] As used herein, the term “room temperature” generally refers to a temperature in a range of “25° C.±3° C. in the present disclosure.

[0078] As used herein, the term “activation energy” refers to a barrier set by the inhibitor compound, thereby hampering the progress of the corrosion process in the presence of the compound.

[0079] Aspects of the present disclosure are directed to a method for inhibiting / reducing corrosion of a metal article that is susceptible to corrosion, e,g, in an acidic environment using a zinc phthalocyanine (Zn-Pc) compound. In some embodiments, the Zn-Pc compound has a formula (I).

[0080] In some embodiments, R1, R2, and R3 are each independently selected from the group consisting of a hydrogen atom, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, an amine group, a nitro group, and a cyano group. In a preferred embodiment, R1, R2, and R3 are H, as depicted by a compound of formula (II).

[0081] However, a person skilled in the art will appreciate other possible substitutions on the Zn-Pc compound, well within the scope of this invention.

[0082] In some embodiments, the Zn-Pc compound of formula (I) has a ball-type geometry. In some further embodiments, the Zn-Pc compound of formula (II) has a ball-type geometry.

[0083] As used herein, the “ball-type geometry” generally refers to a configuration or shape that resembles a ball. In the present disclosure, the ball-type structure may refer to the physical arrangements of the Zn-Pc compound, whose shape or structure is characterized by a spherical or ball-shaped geometry.

[0084] The structures of the compounds described in the present disclosure may be characterized by nuclear magnetic resonance (NMR) spectroscopy. In some embodiments, the NMR may be collected in a JEOL-LA 500 NMR spectrophotometer, and / or a Bruker 500 MHZ spectrometer using the deuterated DMSO as solvent.

[0085] 1H and 13C NMR spectra may be recorded using the residual DMSO-d6 at δ 2.50 ppm, 13C DMSO-d6 signal at δ 39.52 ppm, as internal standards

[0086] 1H nuclear magnetic resonance (NMR) spectra of the Zn-Pc compound of formula (II) was collected in DMSO. In some embodiments, the Zn-Pc compound of formula (II) has peaks in a range of 6 to 8.9, preferably 6.2 to 8.7, preferably 6.4 to 8.5, preferably 6.6 to 8.3, or even more preferably 6.8 to 8.1. Other ranges are also possible.

[0087] The structures of the compounds described in the present disclosure may be characterized by Fourier transforms infrared spectroscopy (FT-IR). For the Fourier transform infrared spectra characterization, the KBr discs of the samples were prepared by mixing and grounding the samples with KBr powder in mortar with pestle. The mixture was then shaped into discs under mechanical pressure. The samples discs are put into Fourier transform infrared spectra and spectral measurements were recorded, e.g., in a Perkin Elmer FT-IR 180 spectrophotometer acquired in a range of 4000 to 400 centimeter inverse (cm−1) at 4 cm−1 resolution. 20 scans were carried out for each sample.

[0088] In some embodiments, the Zn-Pc compound of formula (II) has a first intense peak in a range of 500 to 750 cm−1, preferably 600 to 700 cm−1; a second intense peak in a range of 750 to 1100 cm−1, preferably 850 to 1000 cm−1; a third intense peak in a range of 1100 to 1600 cm−1, preferably 1160 to 1750 cm−1; and a fourth intense peak in a range of 2950 to 3100 cm−1, preferably about 3067 cm−1 in an FTIR spectrum, as depicted in FIG. 2B. Other ranges are also possible.

[0089] In accordance with an aspect of an exemplary embodiment, the method for inhibiting corrosion of a metal article in contact with a corrosive medium includes contacting the metal article with the corrosive medium comprising an acid and a zinc phthalocyanine (Zn-Pc) compound thereby adsorbing the Zn-Pc compound onto at least one surface of the metal article.

[0090] In one embodiment, the contacting may include first applying a composition containing the Zn-Pc compound onto the at least one surface of the metal article, and drying to form a film on the at least one surface of the metal article. In some embodiments, the applying comprises spraying, brushing, wiping, dipping, dripping, or roll coating the composition containing the Zn-Pc compound onto the at least one surface of the metal article. In some further embodiments, the dying to form the film includes heating the metal article after the applying at a temperature of 20 to 100° C., preferably 25 to 80° C., preferably 30 to 60° C., or even more preferably 40 to 50° C. Other ranges are also possible. In some embodiments, the Zn-Pc compound is present in the composition at a concentration of 0.001 to 50 wt. %, preferably 0.05 to 40 wt. %, preferably 1 to 30 wt. %, preferably 3 to 20 wt. %, preferably 4 to 10 wt. %, or even more preferably about 5 wt. 9%. Other ranges are also possible. In one embodiment, the contacting may further include contacting the corrosive medium with the at least one surface containing the film. In general, applying techniques known to those skilled in the art, especially with respect to coating and anti-corrosion protection, may be employed.

[0091] In one embodiment, the contacting may further include forming the corrosive medium by mixing the acid, the Zn-Pc compound, and an aqueous liquid for an appropriate amount of time. In some embodiments, the aqueous liquid is at least one selected from the group consisting of tap water, ground water, distilled water, deionized water, hard water, and fresh water. In some preferred embodiments, the aqueous liquid may be distilled water, and deionized water.

[0092] In another exemplary embodiment, referring to FIG. 1A, a schematic flow diagram of method 50 for inhibiting corrosion of a metal article in contact with a corrosive medium is illustrated. The order in which the method 50 is described is not intended to be construed as a limitation, and any number of the described method steps may be combined in any order to implement the method 50. Additionally, individual steps may be removed or skipped from the method 50 without departing from the spirit and scope of the present disclosure.

[0093] At step 52, the method 50 includes immersing the metal article in the corrosive medium. In some embodiments, the metal article to be protected may be any metal surface susceptible to corrosion in an acidic environment, including, but not limited to, ferrous metals, low alloy metals (e.g., N-80 Grade), stainless steel, aluminum, copper alloys, brass, nickel alloys, and duplex stainless steel alloys. Such metal articles may be a part of a casing, a pipe, a pump, a screen, a valve, or a fitting of an oil or a gas well and the like. In a preferred embodiment, the metal article is made of aluminum. In a more preferred embodiment, at least one surface of the metal article is made of aluminum, and the at least one surface is immersed in the corrosive medium.

[0094] In some embodiments, the corrosive medium may be an acidic or an alkaline medium. In a preferred embodiment, the corrosive medium is an acidic medium. In some more preferred embodiments, the corrosive medium includes one or more acids selected from hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), acetic acid, hydrofluoric acid (HF), and / or combinations of. In a preferred embodiment, the acid is HCl. Other acids are also possible. In some embodiments, the acid is present in the corrosive medium at a concentration of from 0.05 to 35 wt. %, preferably 5 to 25 wt. %, more preferably 12 to 18 wt. %, and yet more preferably 15 wt. % based on the total weight of the corrosive medium. Other ranges are also possible.

[0095] In some embodiments, the corrosive medium may optionally include, but not limited to, surfactants, thickeners and / or viscosity modifiers, solubility modifiers, humectants, metal protecting agents, sequestrants and / or chelating agents, solidifying agent, sheeting agents, pH modifying components, including alkalinity and / or acidity sources, aesthetic enhancing agents (i.e., colorants, odorants, or perfumes), other cleaning agents, hydro tropes or couplers, and buffers.

[0096] The surfactant present in the corrosive medium may be non-ionic, anionic, cationic, or amphoteric. A non-ionic surfactant has no charged groups in its head. In some embodiments, the non-ionic surfactants may include alkanolamides of fatty acids, that is, amide reaction products between a fatty acid and an alkanolamine compound, such as coconut fatty acid monoethanolamide (e.g., N-methyl coco fatty ethanol amide), coconut fatty acid diethanolamide, oleic acid diethanolamide, and vegetable oil fatty acid diethanolamide. In some further embodiments, the non-ionic surfactants may include alkoxylated alkanolamides of fatty acids, preferably ethoxylated and / or propoxylated variants of the alkanolamides of fatty acids having anywhere from 2 to 30 EO and / or PO molar equivalents, preferably 3 to 15 EO and / or PO molar equivalents, preferably 4 to 10 EO and / or PO molar equivalents, preferably 5 to 8 EO and / or PO molar equivalents per moles of the alkanolamide of the fatty acid (e.g., coconut fatty acid monoethanolamide with 4 moles of ethylene oxide). In some preferred embodiments, the non-ionic surfactants may include amine oxides, such as N-cocoamidopropyl dimethyl amine oxide and dimethyl C6-C22 alkyl amine oxide (e.g., dimethyl coco amine oxide). In some further preferred embodiments, the non-ionic surfactants may include fatty esters, such as ethoxylated and / or propoxylated fatty acids (e.g., castor oil with 2 to 40 moles of ethylene oxide), alkoxylated glycerides (e.g., PEG-24 glyceryl monostearate), glycol esters and derivatives, monoglycerides, polyglyceryl esters, esters of polyalcohols, and sorbitan / sorbitol esters. In some even further preferred embodiments, the non-ionic surfactants may include ethers, such as (i) alkoxylated C1-C22 alkanols, which may include alkoxylated C1-C5 alkanols, preferably ethoxylated or propoxylated C1-C5 alkanols (e.g., dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, diethylene glycol n-butyl ether, triethylene glycol n-butyl ether, diethylene glycol methyl ether, triethylene glycol methyl ether) and alkoxylated C6-C26 alkanols (including alkoxylated fatty alcohols), preferably alkoxylated C7-C22 alkanols, more preferably alkoxylated C8-C14 alkanols, preferably ethoxylated or propoxylated (e.g., cetyl stearyl alcohol with 2 to 40 moles of ethylene oxide, lauric alcohol with 2 to 40 moles of ethylene oxide, oleic alcohol with 2 to 40 moles of ethylene oxide, ethoxylated lanoline derivatives, laureth-3, ceteareth-6, ceteareth-11, ceteareth-15, ceteareth-16, ceteareth-17, ceteareth-18, ceteareth-20, ceteareth-23, ceteareth-25, ceteareth-27, ceteareth-28, ceteareth-30, isoceteth-20, laureth-9 / myreth-9, and PPG-3 caprylyl ether), (ii) alkoxylated polysiloxanes, (iii) ethylene oxide / propylene oxide copolymers (e.g., PPG-1-PEG-9-lauryl glycol ether, PPG-12-buteth-16, PPG-3-buteth-5, PPG-5-buteth-7, PPG-7-buteth-10, PPG-9-buteth-12, PPG-12-buteth-16, PPG-15-buteth-20, PPG-20-buteth-30, PPG-28-buteth-35, and PPG-33-buteth-45), and (iv) alkoxylated alkylphenols.

[0097] Examples of surfactants include, but are not limited to, nonoxynol-9, poloxamers, tergitol, perfluorooctane sulfonate (PFOS), Pentax 99, benzalkonium chloride (BAC), cetylpyridinium chloride (CPC), and benzethonium chloride (BZT), betaines, and amino oxides.

[0098] In some embodiments, thickeners and / or viscosity modifiers include bauxite, bentonite, dolomite, limestone, calcite, vaterite, aragonite, magnesite, taconite, gypsum, quartz, marble, hematite, limonite, magnetite, andesite, garnet, basalt, dacite, nesosilicates or orthosilicates, sorosilicates, cyclosilicates, inosilicates, phyllosilicates, tectosilicates, kaolins, montmorillonite, fullers earth, halloysite, polysaccharide gelling agents (e.g., xanthan gum, scleroglucan, and diutan) as well as synthetic polymer gelling agents (e.g., polyacrylamides and co-polymers thereof), psyllium husk powder, hydroxyethyl cellulose, carboxymethylcellulose, and polyanionic cellulose, poly (diallyl amine), diallyl ketone, diallyl amine, styryl sulfonate, vinyl lactam, laponite. In some embodiments, the chelating agents as sequesteration agents of metal ions, include ethylene diamine tetraacetic acid (EDTA), diethylene triamine pentaacetic acid (DPTA), hydroxyethylene diamine triacetic acid (HEDTA), ethylene diamine di-ortho-hydroxy-phenyl acetic acid (EDDHA), ethylene diamine di-ortho-hydroxy-para-methyl phenyl acetic acid (EDDHMA), ethylene diamine di-ortho-hydroxy-para-carboxy-phenyl acetic acid (EDDCHA). In some embodiments, the stabilizing agents include polypropylene glycol, polyethylene glycol, carboxymethyl cellulose, hydroxyethyl cellulose, polysiloxane polyalkyl polyether copolymers, acrylic copolymers, alkali metal alginates and other water-soluble alginates, carboxyvinyl polymers, polyvinylpyrollidones, polyacrylates. In some embodiments, the dispersing agents include polymeric or co-polymeric compounds of polyacrylic acid, polyacrylic acid / maleic acid copolymers, styrene / maleic anhydride copolymers, polymethacrylic acid and polyaspartic acid. In some embodiments, the scale inhibitors include sodium hexametaphosphate, sodium tripolyphosphate, hydroxyethylidene diphosphonic acid, aminotris(methylenephosphonic acid (ATMP), vinyl sulfonic acid, allyl sulfonic acid, polycarboxylic acid polymers such as polymers containing 3-allyloxy-2-hydroxy-propionic acid monomers, sulfonated polymers such as vinyl monomers having a sulfonic acid group, polyacrylates and copolymers thereof. In some embodiments, the defoaming agents include silicone oils, silicone oil emulsions, organic defoamers, emulsions of organic defoamers, silicone-organic emulsions, silicone-glycol compounds, silicone / silica adducts, emulsions of silicone / silica adducts.

[0099] In some embodiments, the metal article is in contact with the corrosive medium at a temperature of 290 to 340 Kelvin (K), or preferably at a temperature from 300 to 330 K, or preferably at a temperature from 305 to 325 K, or preferably at a temperature from 310 to 320 K. Other ranges are also possible. In a preferred embodiment, the metal article is in contact with the corrosive medium at a temperature of 295 to 335 K. In some embodiments, at least one surface of the metal article is in contact with the corrosive medium from 298 to 333K, preferably from 300 to 330 K, preferably from 305 to 325 K, or preferably from 310 to 320 K. Other ranges are also possible.

[0100] At step 54, method 50 includes introducing the zinc phthalocyanine (Zn-Pc) compound into the corrosive medium in contact with the metal article, thereby adsorbing the Zn-Pc compound onto at least one surface of the metal article. In some embodiments, the Zn-Pc compound is present in the corrosive medium in an amount of from 0.001 to 1 mmol / L, or preferably in an amount ranging from 0.1 to 0.8 mmol / L, or preferably in an amount ranging from 0.2 to 0.6 mmol / L, or most preferably in an amount ranging from 0.01 to 0.4 mmol / L. Other ranges are also possible.

[0101] In some embodiments, the metal article is in contact with the corrosive medium containing the Zn-Pc compound for at least 12 hours, preferably at least 24 hours, preferably at least 12 days, preferably at least 24 days, preferably at least 36 days, or even more preferably at least 48 days. Other ranges are also possible.

[0102] In some embodiments, the Zn-Pc compound is adsorbed on at least one surface of the metal article (partially or wholly) further to the introduction of the Zn-Pc compound in the corrosive medium by forming a barrier layer in the form of a composite. In some embodiments, at least 90%, preferably at least 80%, preferably at least 60%, preferably at least 50%, preferably at least 40%, and most preferably at least 70% of the at least one surface of the metal article is covered by the film of the Zn-Pc compound. Other ranges are also possible. In some embodiments, when the metal article is aluminum, at least 70% of the at least one surface of the metal article is covered by the film of the Zn-Pc compound. The percentage as referred here is based on a total surface area of the at least one surface of the metal article.

[0103] Referring to FIGS. 7A and 7F, the surface of the metal article containing the barrier layer has a smoother surface morphology compared to the surface of the metal article in contact with a corrosive medium without the presence of the Zn-Pc compound. In some embodiments, the barrier layer contains irregular shaped aggregates formed after contacting with the solution including the acid. In some embodiments, the aggregates have an average particle size in a range of 0.1 to 50 micrometers (μm), preferably 0.5 to 20 μm, preferably 1 to 10 μm, or even more preferably 3 to 5 μm. In some further embodiments, the barrier layer has an average thickness in a range of 10 to 1000 nanometers (nm), preferably 100 to 800 nm, preferably 200 to 700 nm, preferably 300 to 600 nm, or even more preferably 400 to 500 nm. Other ranges are also possible.

[0104] In some embodiments, the Zn-Pc compound is adsorbed onto the surface of the metal article via a chemical interaction, an electrochemical interaction, or a combination thereof. In some embodiments, the chemical interaction includes at least one of chemical reaction, chemical bonding, chemical dissolution, chemical precipitation, chemical adsorption, chemical desorption, and chemical complexation. In some further embodiments, the chemical interaction is chemical bonding which involves the formation of chemical bonds between atoms or molecules of the metal article and molecules of the NHc composite. In some preferred embodiments, the chemical bonding includes covalent bonding, ionic bonding, and metallic bonding, hydrogen bonding, van der Waals forces, and dipole-dipole interactions. In some most preferred embodiments, iron atoms of the metal article are covalently bonded to the Zn-Pc compound. In some embodiments, the electrochemical interaction includes at least one of oxidation, reduction, ionization, and dissolution of the Zn-Pc compound in the acid containing corrosive medium. In some further embodiments, the electrochemical interaction occurs between the metal article surface and the surrounding environment that led to the deterioration of the metal.

[0105] In some embodiments, the scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) analysis may be conducted to determine and analyze the surface morphology, as well as the elemental mapping of Al, O, C, N, and Zn elements of a metal article specimen immersed in a corrosive medium in the presence / absence of the ball-type Zn-Pc compound. In some embodiments, the SEM analysis may be carried out on a JEOL-SEM analyzer (manufactured by JEOL, 11 Dearborn Road Peabody, MA, USA). In some further embodiments, the elemental mapping of Al, O, C, N, and Zn elements present in the metal article may be determined by EDS analysis. In this regard, a sample may be spread on a copper-covered stump. The sample was used to ensure proper analysis and high quality, and the image was magnified a million times. All the measurement may be conducted at ambient temperature.

[0106] In some embodiments, the at least one surface of the metal article after the introducing the Zn-Pc compound includes about 0.1 to 1 wt. % carbon, preferably about 0.25 to 0.75 wt. % carbon, or even more preferably about 0.4 to 0.6 wt. % carbon; about 0.1 to 1 wt. % nitrogen, preferably about 0.25 to 0.75 wt. % nitrogen, or even more preferably about 0.4 to 0.6 wt. % nitrogen; about 1 to 4 wt. % oxygen, preferably about 1.5 to 3.5 wt. % oxygen, or even more preferably about 2 to 3 wt. % oxygen; about 0.1 to 1 wt. % zinc, preferably about 0.25 to 0.75 wt. % zinc, or even more preferably about 0.4 to 0.6 wt. % zinc; and about 90 to 99.9 wt. % aluminum, preferably about 92 to 97 wt. % aluminium, or even more preferably about 94 to 96 wt. % aluminium, each wt. % based on the total weight of the metal article, as determined by energy dispersive X-ray spectroscopy (EDS). Other ranges are also possible. In the most preferred embodiment, the at least one surface of the metal article includes about 0.53 wt. % carbon, about 0.36 wt. % nitrogen, about 2.19 wt. % oxygen, about 0.52 wt. % zinc, and about 96.41 wt. % aluminum, each wt. % based on the total weight of the metal article, as depicted in FIG. 8B and determined by EDS. Other ranges are also possible.

[0107] In some embodiments, the at least one surface of the metal article in the absence of the Zn-Pc compound includes about 10 to 20 wt. % carbon, preferably about 12 to 18 wt. % carbon, or even more preferably about 14 to 16 wt. % carbon; about 1.5 to 4 wt. % nitrogen, preferably about 1.8 to 3.7 wt. % nitrogen, or even more preferably about 2.1 to 3.4 wt. % nitrogen; about 12 to 32 wt. % oxygen, preferably about 15 to 28 wt. % oxygen, or even more preferably about 18 to 24 wt. % oxygen; and about 50 to 70 wt. % aluminum, preferably about 52 to 68 wt. % aluminium, or even more preferably about 54 to 66 wt. % aluminium, each wt. % based on the total weight of the metal article, as determined by energy dispersive X-ray spectroscopy (EDS). Other ranges are also possible. In the most preferred embodiment, the at least one surface of the metal article in the absence of the Zn-Pc compound includes about 15.63 wt. % carbon, about 2.42 wt. % nitrogen, about 22.63 wt. % oxygen, and about 59.32 wt. % aluminum, each wt. % based on the total weight of the metal article, as depicted in FIG. 8A and determined by EDS. Other ranges are also possible.

[0108] In some embodiments, the metal article has a corrosion rate of about 75 to 475 millimeter penetration per year (mmpy), preferably about 100 to 450 mmpy, preferably about 125 to 425 mmpy, preferably about 150 to 400 mmpy, preferably about 175 to 375 mmpy, preferably about 200 to 350 mmpy, preferably about 225 to 325 mmpy, preferably about 250 to 300 mmpy, and most preferably 50 to 500 mmpy when at least one surface of the metal article is in contact with the corrosive medium at from 298 to 333K, preferably from 300 to 330 K, preferably from 305 to 325 K, and more preferably from 310 to 320 K. Other ranges are also possible. In some embodiments, the Zn-Pc compound is present in the corrosive medium in an amount of from 0.001 to 1 mmol / L, or preferably in an amount of from 0.1 to 0.8 mmol / L, or preferably in an amount of from 0.2 to 0.6 mmol / L, or most preferably in an amount of from 0.01 to 0.4 mmol / L. Other ranges are also possible.

[0109] In some embodiments, the method of the present disclosure exhibits an inhibition efficiency of 5 to 80%, preferably an inhibition efficiency of 10 to 70%, preferably an inhibition efficiency of 20 to 60%, preferably an inhibition efficiency of 30 to 50%, most preferably an inhibition efficiency of 10 to 75% based on an initial weight of the metal article, when at least one surface of the metal article is in contact with the corrosive medium at from 298 to 333K, or preferably from 300 to 330 K, or preferably from 305 to 325 K, or preferably from 310 to 320 K. Other ranges are also possible. In some embodiments, the Zn-Pc compound is present in the corrosive medium in an amount of from 0.001 to 1 mmol / L, or preferably in an amount of from 0.1 to 0.8 mmol / L, or preferably in an amount of from 0.2 to 0.6 mmol / L, or most preferably in an amount of from 0.01 to 0.4 mmol / L. Other ranges are also possible.

[0110] In some embodiments, the metal article is made of aluminum. Here, the metal article has an activation energy of 5 to 15 kilojoules per mole (KJ / mol), or most preferably 6 to 14 KJ / mol when at least one surface of the metal article is in contact with the corrosive medium at from 298 to 333K, or preferably from 300 to 330 K, or preferably from 305 to 325 K, or preferably from 310 to 320 K, and the Zn-Pc compound is present in the corrosive medium in an amount of from 0.001 to 1 mmol / L, or preferably in an amount of from 0.1 to 0.8 mmol / L, or preferably in an amount of from 0.2 to 0.6 mmol / L, or most preferably in an amount of from 0.01 to 0.4 mmol / L. Other ranges are also possible.

[0111] In an embodiment, the metal article includes aluminum, and at least one surface of this metal article has a smoother surface morphology compared to a same surface of the metal article in contact with the corrosive medium in the absence of the Zn-Pc compound.

[0112] Referring to FIG. 1B, a schematic flow diagram of the method 100 for preparing the Zn-Pc compound is illustrated. The order in which the method 100 is described is not intended to be construed as a limitation, and any number of the described method steps may be combined in any order to implement the method 100. Additionally, individual steps may be removed or skipped from the method 100 without departing from the spirit and scope of the present disclosure.

[0113] At step 102, the method 100 includes mixing and heating a nitrophthalonitrile of formula (III), a biphenol of formula (IV) and DMSO in the presence of a base to form a precursor.

[0114] In some embodiments, R1, R2, and R3 are each independently selected from the group consisting of a hydrogen atom, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, an amine group, a nitro group, and a cyano group. In a preferred embodiment, the nitrophthalonitrile is 3-nitrophthalonitrile. In a preferred embodiment, the biphenol is 4,4′-dihydroxybiphenyl.

[0115] In some embodiments, a weight ratio of nitrophthalonitrile of formula (III) to biphenol of formula (IV) is in a range of 1:10 to 10:1, preferably 1:5 to 5:1, preferably 1:2 to 2:1, or even more preferably 1:1. Other ranges are also possible.

[0116] In some embodiments, the base includes sodium carbonate, and potassium carbonate.

[0117] 1H nuclear magnetic resonance (NMR) spectra of the precursor (also referred to as compound (3) in FIG. 1C) was collected in DMSO. In some embodiments, the precursor has peaks in a range of 7 to 8.2, preferably about 7.73, preferably about 7.4, preferably about 7.82, preferably about 7.86, or even more preferably about 7.88, in a 1H NMR spectra. Other ranges are also possible.

[0118] 13C nuclear magnetic resonance (NMR) spectra of the precursor (also referred to as compound (3) in FIG. 1C) was collected in DMSO. In some embodiments, the precursor has peaks in a range of about 105.90, about 113.87, about 116.12, about 116.41, about 120.86, about 122.92, about 128.94, about 129.29, about 136.57, about 137.02, about 154.36, about 160.11, in a 13C NMR spectra. Other ranges are also possible.

[0119] In some embodiments, the precursor has a first intense peak in a range of 1000 to 1400 cm−1, preferably 1180 to 1290 cm−1; a second intense peak in a range of 1400 to 1700 cm−1, preferably 1500 to 1590 cm−1; a third intense peak in a range of 2100 to 2300 cm−1, preferably about 2235 cm−1; and a fourth intense peak in a range of 300 to 3300 cm−1, preferably about 3100 cm−1 in an FTIR spectrum, in the FTIR spectra. Other ranges are also possible.

[0120] At step 104, the method 100 includes heating the precursor and zinc (II) acetate to form a mixture, and washing. In some embodiments, a molar ratio of the precursor to zinc (II) acetate is ia range of 1:10 to 10:1, preferably 1:5 to 5:1, preferably 1:2 to 2:1, or even more preferably 1:1. Other ranges are also possible. In some embodiments, the mixture is heated to a temperature in a range of 220-300° C., preferably 230° C., preferably 240° C., preferably 250° C., preferably 260° C., preferably 270° C., preferably 280° C., and more preferably at 290° C. for 5 to 480 minutes, preferably 10 to 240 minutes, preferably 15 to 120 minutes, preferably 20 to 60 minutes, or even more preferably about 30 minutes. The mixture was further washed with water and methanol to remove any unreacted reactants / impurities to obtain the Zn-Pc compound.EXAMPLES

[0121] The following examples demonstrate methods of preventing / reducing / inhibiting corrosion of a metal surface from a corrosive medium using a zinc phthalocyanine (Zn-Pc) compound, as described herein. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.Example 1: Materials

[0122] All chemicals and reagents used are of analytical quality and were used as supplied. The aluminum specimen, containing about 98.5% pure aluminum, underwent precision cutting to produce pieces with specific dimensions. These meticulously crafted segments measured, e.g., preferably about 5 centimeters in length, preferably about 2 centimeters in width, and preferably about 0.04 centimeters in thickness. This prepared aluminum material ensured uniformity and accuracy in the procedures described below. The chemicals such as zinc acetate, 3-nitrophthalonitrile, 4,4-biphenol, anhydrous potassium carbonate, dimethyl sulfoxide (DMSO), methanol, and acetic acid were purchased from Sigma Aldrich.Example 2: Preparation of Compound (3)

[0123] A mixture of compound (1) 3-nitrophthalonitrile (0.6497 g, 3.7 mmol) and compound (2) 4,4′-dihydroxybiphenyl (0.604 g, 3.2 mmol) in 20 ml of dry DMSO was stirred at room temperature under Ar. Then K2CO3 (0.9042 g 6.54 mmol) was added to the mixture over a period of 2 h (See: Keller et al. Journal of Polymer Science Part A: Polymer Chemistry 26 (12) (1988) 3199-3212, which is incorporated herein by reference in its entirety). After stirring the mixture for 72 h, the mixture was heated for 2 h at 40° C. The reaction mixture was poured into cold water (100 ml). The resulting precipitate was filtered and washed with water and ethanol. The solid was separated by column chromatography using CHCl3 / acetone 9:1 to give compound 3 (0.1637 g 0.22807 mmol). The resulting new compound was confirmed by Fourier-Transform Infrared (FT-IR) (FIG. 2A) with KBr pellets. A piece of evidence for the successful synthesis of compound (3) is the band's appearance (C—O—C) at 1290 / 1180 cm-1, and the disappearance of the (OH) peak and Ar (C═C) peaks at 1590 / 1500 cm−1. 1H nuclear magnetic resonance (NMR) spectra were recorded in DMSO-d6 confirming the desired compound's aromatic proton (Ar—H). 13C NMR shows twelve environments, the unique peaks are Sp CN around 115, Sp2 C═C around 130, Sp3 C—C around 114, and C—Ar around 160.

[0124] FT-IR (KBr): 3100 (Ar—CH), 2235 (CN), 1590 / 1500 (C═C), and 1290 / 1180 (C—O—C). 1H NMR (500 MHz DMSO-d6) δ, (ppm)=7.73 (d, 4H), 7.4 (dd, 2H), 7.82 (d, 2H), 7.86 (d, 4H), 7.88 (t, 2H). 13C NMR (50 MHz, DMSO-d6) δ, (ppm): 105.90, 113.87, 116.12, 116.41, 120.86, 122.92, 128.94, 129.29, 136.57, 137.02, 154.36, 160.11. M.p. 289° C.Example 3: Synthesis of Ball-Type Zinc Phthalocyanine (Zn-Pc) (Compound 4)

[0125] A mixture of compound 3 (0.312 g 0.1566 mmol) as depicted in FIG. 1C and zinc (II) acetate (0.03 g 0.1626 mmol) was heated gradually in a sealed glass tube for 3 h and 30 min under Argon atmosphere at 290° C. After cooling to room temperature, the green solid was washed with hot water and hot methanol. Then, the product was dissolved in acetic acid, filtered, and dried to yield 0.1406 g (0.074607 mmol) of compound 4. UV-Vis (DMSO), Amax (nm): 697, and 322. FT-IR (ATR) (μmax / cm−1): 3067 (Ar—CH), 1723 (CO), 1474 (C═O), and 1266 / 1244 / 1163 (C—O—C). 1H NMR (500 MHz DMSO-d6) δ, (ppm)=6.90-8 (Ar—H). M.p.>386° C.Example 4: Apparatus and Methods

[0126] The chemical structures of all synthesized compounds were confirmed by using Fourier transform infrared (FTIR), nuclear magnetic resonance (H1, 13C 500 MHZ NMR), a fourth harmonic (266 nm), high energy Q-switched Nd-YAG (model: QUV-266-5) Laser-induced breakdown spectroscopy, and FP-8500 photoluminescence spectroscopy.Example 5: Corrosion Measurements

[0127] A thorough polishing process was employed using various grades of emery papers to prepare the aluminum samples. This procedure ensured that the surface of each sample was smooth and free from imperfections. Following the polishing step, the samples were meticulously cleaned by sequentially washing them with acetone to remove any residual contaminants, followed by distilled water to ensure purity. After this rigorous cleaning regimen, the aluminum samples were carefully dried, leaving them in an optimal state for subsequent analyses and investigations, where surface quality and cleanliness were of utmost importance. The corrosive medium is 1 M HCl, which was obtained by the dilution of concentrated HCl (37%) supplied by Fisher Scientific Company, using distilled water.Example 6: Gravimetric Measurements

[0128] The pre-polished aluminum coupons were used as supplied and freely suspended in glass bottles containing 50 mL of 1 M HCl solution with and without different amounts of Zn-Pc. After an appropriate period of time, the aluminum coupons were withdrawn from the test solution and dipped in fresh 1 M HCl solution to dislodge the corroded residues. This was followed by washing with distilled water, then acetone, and drying using a heat gun.

[0129] The mass difference of the aluminum coupons before immersion in 1 M HCl and after is used as weight loss. The weight loss of the aluminium sample was determined in the inhibited and uninhibited 1 M HCl solution for 24 h. The results as depicted in Table 1 show that the inhibition efficiency increases with the increasing concentration of compound 4, showing enhanced metal surface coverage by the compound thereby blanketing the aluminium surface from the aggressive medium (See: Haludu et al., Int. J. Electrochem. Sci. 12 (10) (2017) 9061-9083; Verma et al. RSC Adv. 6 (2016) 15639-54, which is incorporated herein by reference in its entirety). The effect of temperature (293-333 K) in Table 1 showed a decline in the inhibition efficiency as the temperature was elevated. This could be ascribed to the diminishing of the electrostatic force of attraction between the metal surface and the inhibitor due to the increased kinetic energy of the inhibitor and the result is an acceleration in the dissolution of the metal (See: Elsharif et al. J. Mol. Liq. 319 (2020) 114162, which is incorporated herein by reference in its entirety). The inhibition efficiency (IE), and corrosion rate (mmpy) were computed according to Eqs. 1 and 2 respectively:IE⁢ %=Wblank-WinhWblank×100(1)CR(mmpy)=87.6×WAtr(2)where Wblank and Winh stand for the respective average weight losses (mg) of aluminum coupons in pure 1 M HCl and in the presence of Zn-Pc, A stands for the surface area (cm2), t is the immersion time and r is the density of mild steel (g / cm−3).Example 7: Surface CharacterizationThe surface morphology of aluminum coupons were examined by immersing the aluminum coupons in 1 molar hydrochloric acid, in the presence and absence of the zinc ball-type phthalocyanine (compound 4 of formula (II) as depicted in FIG. 1C). A scanning electron microscope (SEM) was used to compare and analyze the surface characteristics. Prior to SEM analysis, any changes in mass due to the interactions was performed by gravimetric analysis. Subsequently, the samples underwent a thorough cleansing process involving acetone and water, followed by gentle drying at room temperature to ensure the removal of any residual contaminants. Additionally, Energy Dispersive X-ray Spectroscopy (EDS) was employed to identify and quantify various components present on the aluminum surface. Therefore, the influence of the zinc ball-type phthalocyanine (compound 4) on the examined aluminum surfaces was revealed by the chemical composition.Example 8: Laser-Induced Breakdown Measurements

[0131] A fourth harmonic (266 nm), high energy Q-switched Nd-YAG pulsed Laser (model: QUV-266-5), with an output pulse duration of 8 ns, repetition rate of 20 Hz, and maximum energy up to 50 mJ, was used in the LIBS system. A UV convex lens with a focal length of 30 nm collimated and focused the beam on the sample, and the plasma was collected by an optical fiber supported by a tiny lens and linked to a 500 mm spectrograph (Andor SR 500i A). The sample was continuously moving on an X-Y translational stage to prevent building a deep crust during the LIBS analysis. Setting the detection system (ICCD, model iStar 320 T, 690 X 255 pixels) as follows: A total of 25 accumulations and a gate width of 2 μs were chosen and applied for all the recorded LIBS setups as described in (See: A. M. Alhasmi, M. A. Gondal, M. M. Nasr, S. Shafik, Y. B. Habibullah, Detection of toxic elements using laser-induced breakdown spectroscopy in smokers' and nonsmokers' teeth and investigation of periodontal parameters, Applied optics 54 (24) (2015) 7342-7349, which is incoporated herein by reference in its entirety).Example 9: Calculations of Structural Models

[0132] Structural models of the ball-type zinc phthalocyanine (Zn-Pc) was built using the Gauss View 5.0 GUI (See: R. K. Dennington, J. Millam, GaussView, Version 5, Semichem Inc., Shawnee Mission, KS (2009), which is incoporated herein by reference in its entirety) and geometrically optimized using the Gaussian 16 modeling suite. The quantum mechanical density functional theory (DFT) method was used at the hybrid B3LYP functional, and the Pople's 6-31G* and the Stuttgart-Dresden (SDD) effective core potential (ECP) basis sets for the non-metals (C, H, N, O) and the metal (Zn) atoms, respectively. These basis sets have proven to be effective in calculating molecular geometries, structural interactions, and yield valid estimations of solvation energies in simulations involving implicit solvent models. Moreover, they yield results with good agreement with the above findings (See: F. M. Valadi, S. Shahsavari, E. Akbarzadeh, M. R. Gholami, Preparation of new MOF-808 / chitosan composite for Cr (VI) adsorption from aqueous solution: Experimental and DFT study, Carbohydrate Polymers 288 (2022) 119383; M. Malhotra, M. Puglia, A. Kalluri, D. Chowdhury, C. V. Kumar, Adsorption of metal ions on graphene sheet for applications in environmental sensing and wastewater treatment, Sensors and Actuators Reports 4 (2022) 100077; and K. Mohan, A. Purushothaman, D. Janardanan, K. R. Haridas, Experimental and theoretical studies of azo derivatives in terms of different donors, acceptors and position isomerism: Synthesis, characterization and a combined electronic absorption, electrochemical and DFT study, Journal of Molecular Structure 1249 (2022) 131621, each of which is incorporated herein by reference in their entireties), at a more modest computational cost (See: I. Abdulazeez, M. Khaled, A. A. Al-Saadi, Impact of electron-withdrawing and electron-donating substituents on the corrosion inhibitive properties of benzimidazole derivatives: A quantum chemical study, Journal of Molecular Structure 1196 (2019) 348-355; and A. M. Elsharif, I. Abdulazeez, M. A. Almarzooq, S. A. Haladu, Synthesis, and experimental evaluation of novel 4-(-3-(2-hydroxyethoxy)-3-oxopropenyl)-1,2-phenylene nanohybrid derivatives as potential corrosion inhibitors for mild steel in 1 M HCl, Journal of Industrial and Engineering Chemistry 116 (2022) 474-488, which is incorporated herein by reference in its entirety). The structure was optimized to the minima on the potential energy surface without enforcing symmetry restrictions. The PCM-SCRF model of solvation was chosen (See: C. C. Nnadiekwe, U. Mustapha, I. Abdulazeez, K. Alhooshani, A. A. J. S. Al-Saadi, Interfaces, Alkali metal ion-doped heptazine-based g-C3N4 quantum dots for efficient adsorption of methyl blue: A DFT perspective 38 (2023) 102852; and M. Umar, C. C. Nnadiekwe, I. Abdulazeez, K. Alhooshani, A. A. Al-Saadi, Nitrogen-Enhanced Charge Transfer Efficacy on the Carbon Sheet: A Theoretical Insight Into the Adsorption of Anionic Dyes, Arabian Journal for Science and Engineering 47 (1) (2022) 419-427, each of which is incorporated herein by reference in their entireties), and the solvent depicted as water. Acid media simulation was conducted by simply protonating the high electron density oxygen atoms within the molecule and adjusting the charge to match the overall added protons to the system. Reactivity descriptors were calculated according to the Pearson's DFT-Koopman theorem derived from the energy of the highest occupied molecular orbital (EHOMO) and the lowest un-occupied molecular orbital (ELUMO) (See: R. G. Pearson, Absolute electronegativity and hardness: application to inorganic chemistry, Inorganic Chemistry 27 (4) (1988) 734-740, which is incorporated here by reference in its entirety). These include the HOMO-LUMO energy gap (ΔEg), electronegativity (χ), global hardness (η) and the dipole moment (μ).Example 10: Results

[0133] Phthalonitriles (1) are chosen as the starting material for the synthesis of Pc complexes. 3-nitrophthalonitrile, a diphthalonitrile, was utilized to create ball-type Pcs, as illustrated in FIG. 1C. 3-nitrophthalonitrile and 4,4′-dihydroxybiphenyl in dry DMSO was stirred at room temperature under Ar. Then K2CO3 was added to the mixture as a base. After stirring the mixture for 72 h, the mixture was heated for 2 h at 40° C. After the workup, the resulting new compound was confirmed by FTIR (FIG. 2A) with KBr pellets. The synthesis of compound (3) is the band's appearance (C—O—C) at 1290 / 1180 cm−1, and also, the disappearance of the (OH) peak. Ar (C═C) peaks at 1590 / 1500 cm−1. 1H NMR spectra were recorded in DMSO-d6 confirming the desired compound's aromatic proton (Ar—H). 13C NMR shows twelve environments, the unique peaks are sp CN around 115, sp2 C═C around 130, sp3 C—C around 114, and C—Ar around 160.

[0134] The ball-type zinc phthalocyanine was obtained in low yield. The Pc structure was confirmed using FTIR (FIG. 2B), 1H NMR UV-Vis, and laser-induced breakdown spectroscopy. The IR spectra clearly exhibit the disappearance of the distinctive C≡N stretch from the spectrum after the conversion to Pc, confirming that metaled Pc was formed. The 1H NMR spectra of zinc Pc in DMSO was difficult to interpret, but it showed the presence of aromatic protons in the aromatic area. The aromatic protons were detected at nearly 6.90-8 ppm in the 1H NMR spectra of zinc Pc, which is attributable to the 4,4′-dihydroxybiphenyl substitution in the ball-type complex. Furthermore, the resulting peaks were quite broad, as is typical of face-to-face complexes.

[0135] The compound (4) was further characterized by ultraviolet-visible (UV-vis) spectra. Compound (4) have regular electronic spectra with two significant absorption bands, one in the UV range around 300-400 nm (B band or Soret) and the other in the visible region around 600-800 nm (Q band) due to the π→π* transition from the macrocyclic structure, the molar absorptivity frequently exceeds 10−5 L·mol−1·cm−1. Ball-type phthalocyanine (Pcs)′ electrical and other characteristics drastically depend on the bridging compounds, metals, and solvent. The degree of interaction is also affected by the bridging substituents and the distance between two Pc molecules of the ball-type Pcs. A slightly less intense absorption band (Q band) was observed in the electronic spectra of ball-type zinc phthalocyanine (compound 4) (FIG. 3) at 697 nm, which coincides with the π→π*transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). Aggregation is demonstrated by the low intensity and broadening of the Q bands and the intensity of the B bands of ball-type zinc phthalocyanine (compound 4). The electrical absorption spectra with the exception that the Q band at 697 nm is not divided due to the existence of a higher energy shoulder at 609 nm. This is consistent with the excitation coupling theory (See: Şengül et al. Dalton Transactions 41 (25) (2012) 7559-7572, which is incorporated herein by reference in its entirety). Because of the deeper level of LUMO transition, compound 4 exhibits high absorption in the UV area between 290 and 400 nm (B band).

[0136] The compound (4) was further characterized by photoluminescence (PL). PL is an effective probe for excited states because its features such as quantum yields, spectra, time frame decay, and temperature dependence can provide useful information. The (PL) spectrum of the ball-type Zn-Pc (compound 4) to examine the photogenerated charge transfer process since it is an effective approach to measure the photoinduced charge separation behavior. The luminescence characteristics of the materials and their photoluminescence spectra in the visible band from 200 to 800 nm (FIG. 4). The photoluminescence and corresponding excitation spectra were obtained at room temperature using FP-8500 Fluorescence Spectrometer. The sample was excited with a wavelength of 220 nm. The photoluminescence excitation spectra of the prepared ball-type Zn-Pc (compound 4) showed two shoulders of emission in the blue-green region at 300 and 400 nm. This might be because of the evident photogenerated charge recombination in the excited molecules (See: Yu et al. Physical Chemistry Chemical Physics 16 (9) (2014) 4106-4114; Bhattacharjee et al. The Journal of Physical Chemistry C 121 (1) (2017) 676-683, which is incorporated herein by reference in its entirety). The transition metal influences the intensity of the spectrum. In phthalocyanines, a phenomenon known as diamagnetic quenching occurs, which reduces the intensity of the spectra. The observed spectrum demonstrates that phthalocyanines are photosensitive (See: Gürel et al. Dalton Transactions 44 (13) (2015) 6202-6211; Liu et al. Sensors 15 (1) (2014) 642-655, which is incorporated herein by reference in its entirety).

[0137] The weight loss of the aluminium sample was determined in the inhibited and uninhibited 1 M HCl solution for 24 h. The results as depicted in Table 1 show that the inhibition efficiency rises with the rise in Zn-Pc concentration, implying increased metal surface coverage by the compound thereby blanketing the aluminium surface from the aggressive medium. The effect of temperature (293-333 K) was also examined. The result (Table 1) revealed a decline in the inhibition efficiency as the temperature was elevated. This could be ascribed to the diminishing of the electrostatic force of attraction between the metal surface and the inhibitor due to the increased kinetic energy of the inhibitor and the result is an acceleration in the dissolution of the metal.TABLE 1Inhibition efficiency and corrosion rate data for Aluminiumin 1M HCl with and without Zn-Pc at various temperatures.ConcentrationInhibition efficiency (%)Corrosion rate (mmpy)(mmol / L)298K313K333K298K313K333KBlank———326.13367.03454.950.0148.729.319.2167.40259.49367.810.0450.731.711.6160.70250.88402.170.0768.932.512.3101.50247.72398.790.169.434.410.699.92240.91406.960.472.935.412.68.32236.96397.67Example 11: Mechanism of Inhibition

[0138] The mechanism by which inhibitor compound (compound 4) mitigates corrosion is by adsorption onto the metal surface, which in turn suppresses corrosion (See: Umoren et al. J. Mol. Liq. 219 (2016) 946-58; Christov et al. Corros. Sci. 46 (2004) 1613-20, which is incorporated herein by reference in its entirety). Considering this, adsorption isotherms are applied to provide essential information about the process. Consequently, the widely obeyed Langmuir adsorption isotherm (Eq. 3) was employed.Cinhθ=1Kads+Cinh(3)

[0139] where Cinh, θ, and Kads represent inhibitor concentration (mmol / L), surface coverage (IE / 100), and equilibrium constant (mol / L), respectively. The obtained Langmuir isotherm plot (Cinh / θ versus Cinh) shown in FIG. 5 is linear with an R2 value of 0.999 at 293K, which implies a good correlation with the model. Afterward, the Kads value (7.86×104 mol / L) obtained from the reciprocal of the Langmuir plot's intercept was used to compute the standard free energy of adsorption ΔGadso according to Eq. 4.Δ⁢Gadso=-RT⁢ln⁡(55.5 Kd)(4)where R is the molar gas constant, T is the absolute temperature, and 55.5 is the molar concentration of 1 L of water. The calculated ΔGadso value for Zn-Pc is −37.24 KJ / mol. When the absolute value of ΔGadso is high, the adsorption of the organic inhibitor is assumed to be strong onto the metal surface. Generally, ΔGadso values of around-20 KJ / mol or less negative indicate physisorption, while values around-40 KJ / mol or more indicative of chemisorption. Accordingly, the inhibitor's adsorption mechanism possibly involves a comprehensive (physisorption and chemisorption) mechanism (See: Kosari et al. Corros. Sci. 78 (2014) 138-50, which is incorporated herein by reference in its entirety).Furthermore, the activation energy for the corrosion of the aluminium sample was estimated using the Arrhenius equation (Eq. 5) in the presence and absence of compound 4.log⁢CR=log⁢A-(Ea2.303 RT)(5)where A is the exponential factor, R, T and CR as described earlier. The plot of Log CR VS. 1 / T for both inhibited and uninhibited systems are linear with R2 values close to unity. The results presented in Table 2 showed that the Ea is lower in the blank solution than in the presence of the inhibitor and increases as the inhibitor concentration increases. This shows that the inhibitor compound raises the activation barrier thereby hampering the progress of the corrosion process.TABLE 2Activation and thermodynamic parameters for Aluminiumin 1M HCl with and without compound 4.ConcentrationEa(mM)(KJ mol−1)AR2DH*(KJ mol-1)DS*(J · mol-1K-1)R2Blank2.9140.40.9594.11−182.810.9050.016.94160.00.99913.39−156.480.9990.048.06247.20.99715.98−148.150.9960.0712.111098.10.98125.30−119.600.9770.112.421230.90.98826.01−117.410.9850.413.321702.90.98028.09−111.200.976The thermodynamic parameters (ΔS* and ΔH*) were also calculated using transition state equation (Eq. 6).log⁢CRT=[(log⁢RNh)+(Δ⁢S*2.303T)]-Δ⁢H*2.303RT(6)where N is the Avogadro's number, h is the Planck's constant, R, T and CR as described earlier. A straight line was obtained by plotting Log CR / T as a function of 1 / T (FIG. 6A and FIG. 6B), from which ΔS* and ΔH* were computed from the intercept (Log (R / Nh)+ΔS* / 2.303T) and slope (−ΔH* / 2.303R), respectively.The data (Table 2) showed that the ΔH* values are positive and increased with increase in compound 4 concentration, indicating the process to be endothermic and that the decline in the corrosion rate is assumed to be predominantly controlled by kinetic parameters (See: Aljourani et al. Corros. Sci. 51 (2009) 1836-43, which is incorporated herein by reference in its entirety). On the other hand, the ΔS* values were negative and also increased with increasing concentration of compound 4, showing that, upon the addition of compound 4, the activation complex is more ordered as the corrosion process progresses, which supports the overall decrease in the corrosion rate (See: Elsharif et al. Arab J. Chem. 13 (2020) 5363-76, which is incorporated herein by reference in its entirety).The results of the SEM analysis showed differences in the surface morphology of the aluminum (Al) samples under various conditions. In the absence of compound 4, the surface exhibited severe pitting and rectangular cavities, indicative of extensive corrosion as shown in (FIGS. 7B-7E), however, the freshly polished surface showed no signs of pits or damage (FIGS. 7A-7D). However, when compound 4 was introduced, the level of damage was notably reduced, and a protective film appeared on the surface, covering approximately 70% (FIGS. 7C-7F). The presence of compound 4 played a crucial role in mitigating corrosion and preserving the integrity of the Al surface.The EDS analysis conducted on the aluminum samples yielded distinct elemental compositions when comparing the absence and presence of the compound 4 in 1 M HCl. In the absence of compound (4), the aluminum sample exhibited varying percentages of elements, with 15.63% carbon, 2.42% nitrogen, 22.63% oxygen, and 59.32% aluminum on the surface (FIG. 8A). However, when compound 4 was introduced, notable differences were observed (FIG. 8B). The percentage of oxygen decreased to 2.19%, indicating a reduction in surface oxidation, while the aluminum percentage significantly increased to 96.41%. This transformation in elemental composition indicates that the presence of compound 4 had an impact on altering the surface chemistry of the aluminum samples, reducing oxygen content, and enhancing aluminum concentration, which may have contributed to the observed protective effects against corrosions.Example 12: Corrosion Inhibition Potential-Density Functional Theory (DFT)The corrosion inhibition potential of the isolated compound (4) and the protonated H+-compound (4) molecules in aqueous medium was calculated using DFT. The optimized structural geometries, the HOMO-LUMO orbital distributions and the electrostatic potential (ESP) maps of both molecules are presented in FIG. 9A and FIG. 9B. Apparently, the HOMO-LUMO orbitals are fairly distributed across the aromatic units of the macrocyclic iso-indole fragments and the nitrogen heteroatoms on the compound (4) framework. This shows the potential of compound (4) to donate electron pairs to the vacant d-orbitals of aluminum ions and to accept electron pairs through back-donation during molecular level interactions, in accordance with the molecular orbital theory (See: Gece et al. Corrosion Science 51 (8) (2009) 1876-1878, which is incorporated herein by reference in its entirety). Moreover, the ESP maps of the molecules show high electron density on the bridging oxygen atoms, indicating that the regions likely to undergo charge donation to the aluminum surface ions. ESP is a graphical representation of the charge distribution on the surface of a molecule. It is often characterized by regions in red, which indicates centers of abundant electrons; blue regions, which imply electron-deficient centers; and neutral centers, depicted as green. Others are the greenish-blue regions, which represent the slightly electron-deficient centers, and the yellow regions, which show the slightly electron-rich centers.

[0146] Meanwhile, the electronic properties of the molecules (FIG. 10) vis-à-vis the HOMO-LUMO energy gap (ΔEg), the electronegativity (χ) which represent the electron attraction potential of the molecules, the global hardness (η) which depicts the resistance of the molecules to electron density distortions during interactions, and the dipole moment (μ) which represents the electronic charge separation within the molecules further indicate that while no significant distortion in electronic properties were observed on the molecules of H+—Zn-Pc (H+-compound 4) after protonation, the dipole moment exhibit a 3-fold increase showing stronger electrostatic attractions to the metallic surface. This consequently shows stronger adsorption and corrosion protection of the aluminum surface in the presence of the compound (4) in an acidic medium.

[0147] FIG. 3 and FIG. 4 show that there is a charge transfer that exists between the complex and the metal. Moreover, the weight loss of the aluminium sample which was determined in the inhibited and uninhibited 1 M HCl solution (Table 1) showed that the inhibition efficiency increased with the increasing concentrations of compound 4, indicating increased metal surface coverage by the compound thereby blanketing the aluminium surface from the aggressive medium. The Langmuir isotherm plot (Cinh / θ versus Cinh) shown in FIG. 5 is linear with an R2 value of 0.999 at 293K, showing a good correlation with the model. The resulting ΔGadso free energy of adsorption calculated from the plot for the inhibitor shows a mechanism involving physisorpotion and chemisorption. The thermodynamic data, ΔH*, from Table 2 is positive, increased with increasing concentrations of compound 4, showing the process to be endothermic and indicative of decrease in the corrosion rate. On the other hand, the ΔS* values are negative which also increases with increase in compound 4 concentration, implying that, upon the addition of compound 4, the activation complex is more ordered as the corrosion process progresses, which supports the overall decrease in the corrosion rate. The surface characteristics study by SEM (FIGS. 7C-7F) is indicative of a protective film on the surface of metal when compound 4 is introduced, the level of damage is notably reduced with a protective film appearing on the surface covering approximately 70%.

[0148] Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Claims

1: A method for inhibiting corrosion of a metal article in contact with a corrosive medium, the method comprising:contacting the metal article with the corrosive medium comprising an acid and a zinc phthalocyanine (Zn-Pc) compound thereby adsorbing the Zn-Pc compound onto at least one surface of the metal article;wherein the Zn-Pc compound is present in the corrosive medium in an amount of 0.01 to 1 millimoles per liter (mmol / L);wherein the Zn-Pc compound has a formula (I)wherein R1, R2, and R3 are each independently selected from the group consisting of a hydrogen atom, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, an amine group, a nitro group, and a cyano group.2: The method of claim 1, wherein the metal article is made of aluminum.3: The method of claim 1, wherein the at least one surface of the metal article is made of aluminum.4: The method of claim 1, wherein the metal article is part of a casing, a pipe, a pump, a screen, a valve, or a fitting of an oil or a gas well.5: The method of claim 1, wherein the acid is at least one selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), acetic acid, and hydrofluoric acid (HF).6: The method of claim 1, wherein the contacting the metal article with the corrosive medium is at a temperature of 290 to 340 Kelvin (K).7: The method of claim 1, wherein the metal article has a corrosion rate of about 50 to 500 millimeter penetration per year (mmpy), when the at least one surface of the metal article is in contact with the corrosive medium at from 298 to 333K, and the Zn-Pc compound is present in the corrosive medium in an amount of from 0.01 to 0.4 mmol / L.8: The method of claim 1, wherein contacting the Zn-Pc compound provides an inhibition efficiency of 10 to 75% when the at least one surface of the metal article is in contact with the corrosive medium at from 298 to 333K, and the Zn-Pc compound is present in the corrosive medium in an amount of from 0.01 to 0.4 mmol / L.9: The method of claim 1, wherein the metal article is made of aluminum, and wherein the metal article has an activation energy of 6 to 14 kilojoules per mole (kJ / mol) when the metal article is in contact with the corrosive medium at from 298 to 333K, and the Zn-Pc compound is present in the corrosive medium in an amount of from 0.01 to 0.4 mmol / L.10: The method of claim 1, wherein the Zn-Pc compound has a ball-type geometry.11: The method of claim 1, wherein the Zn-Pc compound has a formula (II)12: The method of claim 1, wherein the Zn-Pc compound absorbed onto the at least one surface of the metal article is present in the form of a film.13: The method of claim 12, wherein at least 70% of the at least one surface of the metal article is covered by the film of the Zn-Pc compound, each % based on a total surface area of the at least one surface of the metal article.14: The method of claim 1, wherein the at least one surface of the metal article is made of aluminum, and wherein the at least one surface has a smoother surface morphology compared to a same surface of the metal article in contact with the corrosive medium in the absence of the Zn-Pc compound.15: The method of claim 14, wherein the at least one surface of the metal article comprises about 0.1 to 1 wt. % carbon, about 0.1 to 1 wt. % nitrogen, about 1 to 4 wt. % oxygen, about 0.1 to 1 wt. % zinc, and about 90 to 99.9 wt. % aluminum, each wt. % based on a total weight of the metal article, as determined by energy dispersive X-ray spectroscopy (EDS).16: The method of claim 15, wherein the at least one surface of the metal article comprises about 0.53 wt. % carbon, about 0.36 wt. % nitrogen, about 2.19 wt. % oxygen, about 0.52 wt. % zinc, and about 96.41 wt. % aluminum, each wt. % based on the total weight of the metal article, as determined by EDS.17: The method of claim 1, further comprising preparing the Zn-Pc compound by:mixing and heating a nitrophthalonitrile of formula (III), a biphenol of formula (IV) and DMSO in the presence of a base to form a precursor; andheating the precursor and zinc (II) acetate to form a mixture, and washing;wherein formula (III) iswherein formula (IV) isandwherein R1, R2, and R3 are each independently selected from the group consisting of a hydrogen atom, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, an amine group, a nitro group, and a cyano group.18: The method of claim 17, wherein the nitrophthalonitrile is 3-nitrophthalonitrile.19: The method of claim 17, wherein the biphenol is 4,4′-dihydroxybiphenyl.20: The method of claim 17, wherein the base comprises sodium carbonate, and potassium carbonate.

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