USING NON-TRIAZOLE COMPOUNDS

TECHNICAL FIELD

[0001] This application relates generally to non-triazole compounds and their use as corrosion inhibitors to inhibit corrosion in aqueous systems.

BACKGROUND

[0002] Corrosion of metal surfaces in water systems is a serious problem. Corrosion can cause undesirable consequences, including loss of heat transfer, increased cleaning frequency, equipment repairs and replacements, shutdowns, environmental problems and the increasing resources and costs associated with each. Some causes of increased corrosion of metal surfaces include high dissolved solids, acidic environments, elevated temperatures, microbiological growth, organic and mineral deposits, and fluids that contain relatively high concentration of gases such as oxygen, hydrogen sulfide, or carbon dioxide.

[0003] Ferrous metals such as stainless steel are commonly used in industrial water systems such as for heat exchangers in cooling waters. Stainless steel has good mechanical and physical properties for long service life, as well as generally good corrosion resistance. However, even stainless steel can be subject to pitting and crevice corrosion.

[0004] Copper and its alloys (all referred to generally as "yellow metals") are also commonly used in cooling water treatment systems for heat exchanger tubing, pump impellers, and various other applications due to the natural corrosion resistance and high thermal conductivity of these metals. However, copper and its alloys are not immune to corrosion in cooling water applications especially in the presence of halogen based oxidizing biocides such as hypochlorous acid (HOC1) or hypobromous acid (HOBr). Current corrosion inhibitors for copper and its alloys include triazole-based compounds, i.e., a heterocyclic compound that includes a five-membered ring of two carbon atoms and three nitrogen atoms. Conventional triazole corrosion inhibitors include tolyltriazole (TT), benzotriazole (BZT), and chlorinated tolyltriazole (Cl-TT). The triazoles work as yellow metal corrosion inhibitors by forming an inhibitor film on the surface of yellow metals through bonding with copper. However, the film formed by triazoles can be disrupted by halogen-based biocides (e.g. H0C1), which can lead to corrosion and equipment failure. The film formed by triazoles on the metal surface is also affected by high free chlorine and it requires additional triazole to repassivate the film for corrosion protection. Additionally, in the bulk water, the triazole inhibitor can react and be degraded by halogen-containing biocide and its corrosion inhibition capacity reduced. Triazole inhibitors and their halogenated derivatives also have high aquatic toxicity which can limit their application in industrial cooling water treatment, and the raw materials required to manufacture triazoles are often impacted by cost fluctuation and supply chain vulnerability.

[0005] These and other issues are addressed by the present disclosure.

SUMMARY

[0006] According to one aspect, this disclosure provides a method of inhibiting corrosion of a corrodible metal surface that contacts a water stream in a water system. The method includes introducing into the water stream at least one non-triazole compound that is selected from a compound that is represented by Formula (I), Formula (II), or Formula (III) below: in which Ri is a polyhydroxy group; R2 and R3 are independently selected from a hydrogen or a hydrocarbon group with the proviso that at least one of R2 and R3 includes a hydrocarbon group; R ₄ is a polyhydroxy group; R ₅ is a hydrocarbon group; R ₆ is a hydrogen or a hydrocarbon group; R7 and R« are independently selected from a hydrogen or a hydrocarbon group with the proviso that at least one of R7 and Rx includes a hydrocarbon group; and R9 is a hydrocarbon group that includes at least one hydroxyl group.

[0007] According to another aspect, this disclosure provides A method of inhibiting corrosion of a yellow metal that contacts a water stream in a water system. The method includes introducing into the water stream at least one non-triazole compound that is selected from a compound that is represented by Formula (I): in which R1 is a polyhydroxy group with 3 to 10 carbon atoms and 2 to 9 hydroxyl groups, and R2 and R3 are independently selected from a hydrogen or a hydrocarbon group with the proviso that at least one of R2 and R3 includes a hydrocarbon group with 3 to 10 carbon atoms. The non-triazole compound is introduced into the water stream in an amount of from 0.5 ppm to 100 ppm.

[0008] According to another aspect, this disclosure provides a method of inhibiting corrosion of a corrodible metal surface that contacts a water stream in a water system. The method includes introducing into the water stream at least one non-triazole compound that is selected from a bicinchoninic acid, an acyl sarcosine, a fatty imidazoline, 8-hydroxyquinoline, a polyamine, a hydroxynapthalene sulfonate, a halogenated imidazole, an alkyl pyridine quat, a modified tertiary amine, an ethoxylated oleylamine, an alkyl dithiophosphate, adenosine, tryptophan, an alkyl thioethylamine, an ethoxylated tallow diamine, an imidazole carboxylate, a urea amine blend, and a fatty diamine.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. l is a graph showing the corrosion of a copper surface when treated with glucamide corrosion inhibitors and a conventional triazole corrosion inhibitor; and

[0010] Fig. 2 is a graph showing the corrosion of a copper surface when treated with other non-triazole corrosion inhibitors.

DETAILED DESCRIPTION OF EMBODIMENTS

[0011] This disclosure provides novel non-triazole chemistries that are effective to prevent corrosion of metal surfaces in contact with water. The non-triazole corrosion inhibitors overcome several of the drawbacks of known triazole-based corrosion inhibitors.

[0012] In embodiments, the non-triazole compounds can be represented by Formula (I), Formula (II), or Formula (III) below.

[0013] Formula (I)

[0014] In Formula (I), Ri is a polyhydroxy group. The polyhydroxy group can include, for example, 2-25 carbon atoms, from 3 to 10 carbon atoms, or from 4 to 7 carbon atoms, and can be linear, branched, cyclic, or heterocyclic, aliphatic or aromatic, saturated or unsaturated. The polyhydroxy group can include from 2 to 24 hydroxyl groups, from 2 to 9 hydroxyl groups, or from 3 to 6 hydroxyl groups, for example. The polyhydroxy group can consist solely of hydroxyl groups, carbon, and hydrogen, or alternatively may include heteroatoms in the hydrocarbon backbone. In some embodiments, the polyhydroxy group is a linear chain having 5 or 6 carbon atoms with 5 or 6 hydroxyl groups. In some embodiments, the polyhydroxy group includes one or more monosaccharide, disaccharide, or trisaccharide moieties.

[0015] In Formula (I), R2 and R ₃ can be independently selected from hydrogen or a hydrocarbon group with the proviso that at least one of R ₂ and R ₃ includes a hydrocarbon group. The hydrocarbon group can be linear, branched, cyclic or heterocyclic, aliphatic or aromatic, saturated or unsaturated. The hydrocarbon group can include from 2 to 20 carbon atoms, from 3 to 10 carbon atoms, or from 4 to 7 carbon atoms, for example. The hydrocarbon group can include one or more of the following atoms/moieties: halogen, heteroatom, amino, aminoalkyl, cyano, alkoxy, hydroxyl, thiol, alkythiol, carbonyl, nitro, phosphoryl, phosphonyl, sulfonyl. If heterocyclic groups are present, they can include an imidazole or a pyridine group, for example. If non-cyclic, the hydrocarbon group can be terminated with an amine or hydroxyl group, for example. If the hydrocarbon group includes heteroatoms, the heteroatoms can be present in the hydrocarbon backbone in numbers of, for example, 1, 2, 3, or 4 heteroatoms, including, e.g., N, O, S. The hydrocarbon group can also be substituted with a halogen atom. In some embodiments R ₂ and R ₃ can form a ring with the nitrogen atom in Formula (I), and in such cases R2 and R3 shall each be deemed to include a hydrocarbon group and share the number of carbon atoms in the ring. In some embodiments, if R2 and R3 form a ring with the nitrogen atom in Formula (I), the ring can include 4 to 7 carbon atoms, 3 to 5 carbon atoms, can optionally form a bicyclic or tricyclic ring, and may optionally also include an oxygen atom, or an additional nitrogen atom. This ring can include, for example, an imidazole moiety. The compound of Formula (I) does not include any triazole groups, and preferably does not include any tetrazole groups.

[0016] Compounds of Formula (I) can be synthesized by reacting a polyhydroxy compound with an amine compound. Exemplary polyhydroxy compounds that can be used in the reaction include derivatives of sugars, sugar acids, polysaccharides, gluconic acid, lactones of sugar acids, and lactones of gluconic acid (e.g., glucono delta lactone). Exemplary amine compounds that can be used include primary amines, secondary amines, diamines (e.g., dimethylaminopropylamine), triamines (e.g., diethylene triamine), cyclic or heterocyclic amines (e.g., morpholine), ethoxyamines (e.g., 3-methoxy propyl amine), alkanolamines (e.g., aminoethyl ethanolamine), imidazolidinones (e.g., 1 -(2 -hydroxy ethyl)-2- imidazolidinone), imidazolines, imidazole, pyrazoles, piperazines (e.g., 1 -(2 -hydroxy ethyl) piperzine), piperidines, and pyrrolidines.

[0017] An exemplary reaction mechanism for synthesizing a compound of Formula (I) is shown below, in which glucono delta lactone is reacted with morpholine in an approximately 1 : 1 molar ratio to produce a glucamide.

[0018] This compound, as well as other glucamide compounds, and other compounds of Formula (I), have been found to be effective to prevent corrosion of metal surfaces in aqueous environments. Other exemplary glucamides of Formula (I) are shown below:

[0019] Formula

(ID

[0020] In Formula (II), R4 is a polyhydroxy group. The polyhydroxy group can include, for example, 2-25 carbon atoms, from 3 to 10 carbon atoms, or from 4 to 7 carbon atoms, and can be linear, branched, cyclic, or heterocyclic, aliphatic or aromatic, saturated or unsaturated. The polyhydroxy group can include from 2 to 24 hydroxyl groups, from 2 to 9 hydroxyl groups, or from 3 to 6 hydroxyl groups, for example. The polyhydroxy group can consist solely of hydroxyl groups, carbon, and hydrogen, or alternatively may include heteroatoms in the hydrocarbon backbone. In some embodiments, the polyhydroxy group is a linear chain having 5 or 6 carbon atoms with 5 or 6 hydroxyl groups. In some embodiments, the polyhydroxy group includes one or more monosaccharide, disaccharide, or trisaccharide moieties. [0021] R ₅ is a hydrocarbon group. The hydrocarbon group can be linear, branched, cyclic or heterocyclic, aliphatic or aromatic, saturated or unsaturated. The hydrocarbon group can include from 2 to 20 carbon atoms, from 3 to 10 carbon atoms, or from 4 to 7 carbon atoms, for example. The hydrocarbon group can include one or more of the following atoms/moi eties: halogen, heteroatom, amino, aminoalkyl, cyano, alkoxy, hydroxyl, polyhydroxyl, thiol, alkythiol, carbonyl, nitro, phosphoryl, phosphonyl, sulfonyl. If non- cyclic, the hydrocarbon can be terminated with an amine or hydroxyl group. If the hydrocarbon group includes heteroatoms, the heteroatoms can be present in the hydrocarbon backbone in numbers of, for example, 1, 2, 3, or 4 heteroatoms, including, e.g., N, O, S, and the hydrocarbon group can also be substituted with a halogen atom. If aromatic groups are present, they can include heterocyclic aromatic groups, including a pyridine group, for example.

[0022] Rs is selected from hydrogen or a hydrocarbon group. The hydrocarbon group can be linear, branched, or cyclic, aliphatic or aromatic, saturated or unsaturated. The hydrocarbon group can include from 1 to 10 carbon atoms, from 1 to 5 carbon atoms, or from 1 to 3 carbon atoms, such as a methyl group, for example. The hydrocarbon group can include one or more of the following atoms/moi eties: halogen, heteroatom, amino, aminoalkyl, cyano, alkoxy, hydroxyl, polyhydroxyl, thiol, alkythiol, carbonyl, nitro, phosphoryl, phosphonyl, sulfonyl. Formula (II) does not include any triazole groups, and preferably does not include any tetrazole groups.

[0023] Compounds of Formula (II) can be synthesized by reacting a polyhydroxy amine compound with a hydrocarbon compound. An exemplary polyhydroxy amine compound that can be used in the reaction is a glucamine. The hydrocarbon compound can include a group that reacts with the amine of the polyhydroxy amine, including at least one of an acid chloride, amide, and ester group.

[0024] An exemplary reaction mechanism for synthesizing a compound of Formula (II) is shown below, in which glucamine is reacted with a pyridinecarboxylic acid methyl ester in an approximately 1 : 1 molar ratio. [0025] Other exemplary compounds of Formula (II) are shown below:

[0026] Formula (III) [0027] In Formula (III), R7 and R« can be independently selected from hydrogen or a hydrocarbon group with the proviso that at least one of R7 and R ₈ includes a hydrocarbon group. The hydrocarbon group can be linear, branched, cyclic or heterocyclic, aliphatic or aromatic, saturated or unsaturated. The hydrocarbon group can include from 2 to 20 carbon atoms, from 3 to 10 carbon atoms, or from 4 to 7 carbon atoms, for example. The hydrocarbon group can include one or more of the following atoms/moieties: halogen, heteroatom, amino, aminoalkyl, cyano, alkoxy, hydroxyl, polyhydroxyl, thiol, alkythiol, carbonyl, nitro, phosphoryl, phosphonyl, sulfonyl. If the hydrocarbon group of R ₇ and/or R ₈ includes heteroatoms, the heteroatoms can be present in the hydrocarbon backbone in numbers of, for example, 1, 2, 3, or 4 heteroatoms, including, e.g., N, O, S, and the hydrocarbon can also be substituted with a halogen atom. In some embodiments, the hydrocarbon group of R ₇ and/or R ₈ can include a polyhydroxy group. The polyhydroxy group can include from 2 to 24 hydroxyl groups, from 2 to 9 hydroxyl groups, or from 3 to 6 hydroxyl groups, for example. The polyhydroxy group can consist solely of hydroxyl groups, carbon, and hydrogen, or alternatively may include heteroatoms in the hydrocarbon backbone. In some embodiments, R ₇ and R ₈ can form a ring with the nitrogen atom in Formula (III), and in such cases R7 and R ₈ shall each be deemed to include a hydrocarbon group and share the number of carbon atoms in the ring. In some embodiments, if R7 and R ₈ form a ring with the nitrogen atom in Formula (III), the ring can include 4 to 7 carbon atoms, or 3 to 5 carbon atoms, can optionally form a bicyclic or tricyclic ring, and may optionally also include an oxygen atom, or an additional nitrogen atom. The ring can include, for example, an imidazole moiety.

[0028] R ₉ is a hydrocarbon group that includes at least one hydroxyl group (e.g., 1 to 3 hydroxyl groups). The hydrocarbon group can be linear, branched, cyclic, or heterocyclic, aliphatic or aromatic, saturated or unsaturated. The hydrocarbon group can include from 2 to 20 carbon atoms, from 2 to 10 carbon atoms, or from 3 to 5 carbon atoms, , for example. In some emboidments, the hydrocarbon group includes 2 to 4 carbon atoms and a single hydroxyl group. The hydrocarbon group can also include one or more of the following atoms/moieties: halogen, heteroatom, amino, aminoalkyl, cyano, alkoxy, thiol, alkythiol, carbonyl, nitro, phosphoryl, phosphonyl, sulfonyl. The compound of Formula (III) does not include any triazole groups, and preferably does not include any tetrazole groups.

[0029] In embodiments, compounds of Formula (III) can be synthesized by reacting a cyclic carbonate ester with an amine. The cyclic carbonate ester can include an ethylene carbonate or propylene carbonate, for example. Exemplary amine compounds that can be used include primary amines, secondary amines, diamines (e.g., dimethylaminopropylamine), triamines (e.g., diethylene triamine), cyclic or heterocyclic amines (e.g., morpholine), ethoxyamines (e.g., 3-methoxy propyl amine), alkanolamines (e.g., aminoethyl ethanolamine), polyhydroxy amines (e.g., glucamine), imidazolidinones (e.g., l-(2-hydroxyethyl)-2- imidazolidinone), imidazolines, imidazole, pyrazoles, piperazines (e.g., 1 -(2 -hydroxy ethyl) piperzine), piperidines, and pyrrolidines.

[0030] An exemplary reaction mechanism for synthesizing a compound of Formula (III) is shown below, in which propylene carbonate is reacted with imidazole in an approximately 1 : 1 molar ratio.

[0031] Other exemplary compounds of Formula (III) are shown below: [0032] Other Non-triazole Compounds

[0033] In addition to Formulas (I), (II), and (III) above, a fourth class of non- triazole compounds that may be useful as corrosion inhibitors can be formed by reacting a compound with multiple carboxylic acid groups, including dicarboxylic acids (e.g., 1H- imidazole-4,5 dicarboxylic acid) or tricarboxylic acids with an amine compound. Exemplary amine compounds that can be used include primary amines, secondary amines, diamines (e.g., dimethylaminopropylamine), triamines (e.g., diethylene triamine), cyclic or heterocyclic amines (e.g., morpholine), ethoxyamines (e.g., 3-methoxy propyl amine), alkanolamines (e.g., aminoethyl ethanolamine), imidazolidinones (e.g., l-(2-hydroxyethyl)-2-imidazolidinone), imidazolines, imidazole, pyrazoles, piperazines (e.g., 1 -(2 -hydroxy ethyl) piperzine), piperidines, and pyrrolidines.

[0034] In addition to the above chemistries, other non-triazole/non-tetrazole compounds that may be useful as corrosion inhibitors in embodiments of the invention include aromatic nitrogen compounds (e.g., bicinchoninic acid, 8-hyroxyquinoline, hydroxynaphthalene sulfonate), amino acid or glycosylamine derivatives (e.g., acyl sarcosines, adensine, tryptophan), imidazoline derivatives (e.g., fatty imidazolines, halogenated imidazoles, imidazole carboxylates, benzimidazole), amine derivatives (e.g., polyamines, alkyl pyridine quat, modified tertiary amines, ethoxylated oleylamines, ethoxylated tallow diamines, urea amine blend, fatty diamines), and sulfur containing compounds (e.g., alkyl dithiophosphates, alkyl thioethylamines).

[0035] Treatment Methods

[0036] At least one non-triazole compound described above can be combined with water that is in contact with a metal surface to inhibit or prevent corrosion of the metal surface. In embodiments, the non-triazole compound may be introduced into open or closed water systems. Further, the non-triazole compound can be applied to the water stream while the water system is on-line. The methods of inhibiting corrosion can be used in aqueous systems including, but not limited to cooling water, cooling towers, water distribution systems, boilers, pasteurizers, water and brine carrying pipelines, storage tanks and the like. In general, water in these aqueous systems is at least 90 wt.% water, at least 95 wt.% water, or at least 99 wt.% water.

[0037] At least one non-triazole compound described above can be combined with the water in the water system in amounts that are effective to form a film of the non-triazole compound(s) on the metal surface and reduce corrosion of the metal surface to a desired degree. The at least one non-triazole compound can be added so that the non-triazole compound is present in the water in amounts of from 0.01 ppm to 500 ppm, from 0.5 ppm to 100 ppm, from 1 ppm to 50 ppm, or from 2 ppm to 15 ppm, for example. The non-triazole compounds can be added to the water continuously, periodically, or intermittently.

[0038] The compounds can be added in response to a measured parameter of the water or of the metal surface, including when a measured amount of corrosion inhibitor drops below a predetermined threshold.

[0039] The non-triazole compounds can be added to the water in the form of a powder or an aqueous solutions. If added as an aqueous solution, the non-triazole compound can be present in amounts of from 1 to 60 wt.% or from 5 to 40 wt.%, for example.

[0040] The metal surface that is in contact with the treated water can include ferrous metals such as steel (e.g., mild steel, stainless steel, etc.), aluminum and its alloys, and yellow metals (e.g., copper and copper-based alloys including bronzes, brasses, etc.). In one aspect, it has been discovered that non-triazole compounds are particularly useful in inhibiting corrosion of yellow metals. In this regard, the non-triazole compounds, and in particular compounds with polyhydroxy groups such as glucamide and glucono-imidazoline derivatives, can prevent corrosion on yellow metals by forming an insoluble protective film on the surface. It is believed that the film is stabilize by a molecular bond with the organic inhibitor and copper and prevents surface interaction with corrosive species.

[0041] The non-triazole inhibitors have improved aquatic toxicity, as compared to conventional azole inhibitors. Accordingly, in some embodiments, the treated water that is in contact with the metal surface is free of or substantially free of triazole compounds, e.g., less than 5 ppm triazole compounds, less than 1 ppm triazole compounds, or less than 0.1 ppm triazole compounds. In particular, the treated water can be free of or substantially free of tolyltri azole, benzotri azole, and chlorinated tolyltri azole.

[0042] In some embodiments, the non-triazole inhibitors can be added to the water in combination with other inhibitor treatment agents including triazoles, polymers, phosphonates, and/or phosphates.

[0043] The non-triazole corrosion inhibitors also have improved halogen stability, and remain effective to inhibit corrosion even in the water that contains halogen-containing biocides or free chlorine. In this regard, it is believed that these halogens do not substantially disrupt the film formed by the above-referenced non-triazole corrosion inhibitors and do not degrade those compounds in the bulk water. Accordingly, in some embodiments, the treated water that is in contact with the metal surface includes at least 0.1 ppm of a halogencontaining biocide and/or free chlorine, at least 0.5 ppm, at least 1 ppm, or from 1 ppm to 10 ppm. Halogen-containing biocides may include, for example, hypochlorous acid or hypobromous acid. Likewise, in some embodiments, methods of the invention include combining a halogen-containing biocide with the treated water in addition to the non-triazole compound.

[0044] In addition to the non-triazole corrosion inhibitor, other components can be added to the water as part of the treatment, including chelating agents, scale inhibitors, dispersants, biocides (such as the halogen-containing biocide noted above), and combinations thereof. These components can be included as part of a treatment composition with the non- triazole corrosion inhibitor or can be added to the water separately. Suitable chelating agents include, for example, citric acid, 2-Butenedioic acid (Z), and their derivatives. Suitable scale inhibitors and dispersants can include one or more of unsaturated carboxylic acid polymers such as polyacrylic acid, homo or co-polymaleic acid (synthesized from solvent and aqueous routes); acrylate/2-acrylamido-2-methylpropane sulfonic acid (APMS) copolymers, acrylate/acrylamide copolymers, acrylate homopolymers, terpolymers of carboxylate/sulfonate/maleate, terpolymers of acrylic acid/ AMPS; phosphonates and phosphinates including 2-phosphonobutane-l,2,4-tricarboxylic acid (PBTC), 1 -hydroxy ethylidene-l,l-diphosphonic acid (HEDP), amino tris methylene phosphonic acid (ATMP), 2-hydroxyphosphonocarboxylic acid (HP A), diethylenetriamine penta(methylene phosphonic acid) (DETPMP), phosphinosuccinic oligomer (PSO); salts of molybdenum and tungsten including nitrates and nitrites; amines such as N,N-diethylhydroxylamine (DEHA), diethyl amino ethanol (DEAE), dimethylethanolamine (DMAE), cyclohexylamine, morpholine, and monoethanolamine (MEA).

[0045] In some embodiments, one or more fluorescent agents can be combined with the non-triazole inhibitor or added to the water together with the non-triazole inhibitor to detect and quantify the amount of inhibitor in the water. In embodiments, the fluorescent agents can include a reactive chemical tracer (e.g., PTSA) that interacts with the non-triazole group in a way that affects the fluorescence intensity and a non-reactive chemical tracer such as a tagged polymer. Suitable fluorescent agents that can be used are described in U.S. Patent No. 10,024,751, the entirety of which is incorporated by reference herein.

[0046] Example 1 [0047] Several non-triazole glucamide compounds and tolyltriazole (as a comparative example) were tested to determine their potential to inhibit corrosion of copper in aqueous systems.

[0048] 1 liter samples of synthetic water were each dosed with 5 ppm of a different glucamide compound (A, B, C, D) according to Formula (I) above and 50 ppm of a standard scale inhibitor. Another 1 liter sample of synthetic water was dosed with 4 ppm of tolyltriazole and 50 ppm of the standard scale inhibitor product. The composition of the synthetic water is shown in Table I below.

Table 1

[0049] The apparatus used for the corrosion testing was a Gamry Multiport Corrosion Cell and Gamry Reference 600+ potentiostat with multiplexor. Copper coupons (CDA110) were added to the sample cells, and the cells were heated to 50°C and maintained at this temperature throughout the testing. The cells were continuously stirred at a speed of 350 rpm. A cylindrical working electrode was submerged into the test solutions, and an LPR sweep (linear polarization resistance) was performed every hour for 18 hours. After the one hour mark, 1 ppm of free chlorine was dosed into the corrosion cell.

[0050] The corrosion rates (in mpy) over the 18 hour period are shown in Fig. 1. As can be seen, the glucamide compounds of Formula (I) exhibit superior corrosion inhibition properties over the entire 18 hour period as compared to the triazole inhibitor. And, unlike the triazole inhibitor, the glucamide corrosion inhibitors do not exhibit any substantial deterioration in corrosion resistance when free chlorine is added.

[0051] Example 2

[0052] Several other classes of non-triazole compounds were tested to determine their potential to inhibit corrosion of copper in aqueous systems using the same testing procedures as in Example 1. These additional classes non-triazole compounds are bicinchoninic acid, acyl sarcosine, fatty imidazoline, 8-hydroxyquinoline, polyamine, hydroxynapthalene sulfonate, halogenated imidazole, alkyl pyridine quat, modified tertiary amine, ethoxylated oleylamine, alkyl dithiophosphate, adenosine, tryptophan, alkyl thioethylamine, ethoxylated tallow diamine, imidazole carboxylate, urea amine blend, and fatty diamine.

[0053] The corrosion rates (in mpy) over the 18 hour period are shown in Fig. 2. As can be seen, these non-triazole compounds exhibit beneficial corrosion resistance over the 18 hour testing period.

[0054] While the invention has been described in conjunction with the specific exemplary embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, exemplary embodiments of the invention as set forth herein are intended to be illustrative, not limiting. There are changes that may be made without departing from the spirit and scope of the invention.