Patent Description:
Copper and copper alloy components are commonly used in industrial systems due to copper's high thermal conductivity and anti-microbial properties. Copper and copper alloys (e.g., bronze and brass) are relatively resistant to corrosion as a result of protective film layers that naturally coat the surface of copper, which include an inner cuprous oxide film layer and an outer cupric oxide film layer. Under anaerobic conditions, these protective layers generally reduce the rate of further corrosion of the metal surface. However, under certain conditions, copper and copper alloys are susceptible to corrosion. In the presence of oxygen and under acidic conditions, oxidation of copper and dissolution of the copper (II) ion into water can occur.

Copper corrosion inhibitors are commonly added to industrial water systems to prevent and reduce dissolution of copper from system surfaces. In particular, the use of nitrogen-containing compounds such as azoles is well known for inhibiting the corrosion of copper and copper alloys. It is generally believed that the nitrogen lone pair electrons coordinate to the metal, resulting in the formation of a thin organic film layer that protects the copper surface from elements present in the aqueous system. Nitrogen-containing compounds such as azoles are also known to precipitate copper (II) from the aqueous solution, hindering corrosion that can occur due to galvanic reactions between copper and other metals.

Oxidizing halogens are commonly used as biocides in industrial systems to control slime and microbiological growth in water. The protective film provided by many azoles erodes in the presence of oxidizing halogens such as chlorine, hypochlorite, and hypobromite, reducing the effectiveness of the corrosion inhibitor. Moreover, a decrease in copper (II) precipitation often occurs in the presence of oxidizing halogens due to halogen attack of the corrosion inhibitor in solution. Thus, in the presence of oxidizing halogens, an excess or continuous injection of corrosion inhibitor is often required to maintain the organic protective film.

A serious concern in the industry is the environmental pollution caused by introduction of toxic corrosion inhibitors into the environment. While many heterocyclic compounds have found wide application as corrosion inhibitors, many commonly used anticorrosive agents such as benzotriazole and its derivatives are non-biodegradable and toxic. The industry is steadily moving toward the development of environmentally-friendly corrosion inhibitors that provide excellent inhibitory activity while having both non-toxic and biodegradable properties.

An environmentally-friendly method of inhibiting metal corrosion would be beneficial to the industry. Moreover, it would be desirable to provide a method that provides protection of copper in the absence and presence of oxidizing halogen agents.

In an embodiment, the invention provides a method for inhibiting corrosion of a metal surface in contact with an aqueous system according to claim <NUM>.

In another embodiment, the invention provides a compound according to claim <NUM>.

The following definitions are provided to determine how terms used in this application, and in particular, how the claims are to be construed. The organization of the definitions is for convenience only and is not intended to limit any of the definitions to any particular category.

For convenience of reference herein, the structure of the compounds of formula (I) is numbered as follows:
<CHM>.

For convenience of reference herein, the structure of the compounds of formula (II) is numbered as follows:
<CHM>.

Whenever a range of the number of atoms in a structure is indicated (e.g., a C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, etc.), it is specifically contemplated that any sub-range or individual number of carbon atoms falling within the indicated range also can be used. Thus, for instance, the recitation of a range of <NUM>-<NUM> carbon atoms (e.g., C<NUM>-C<NUM>), <NUM>-<NUM> carbon atoms (e.g., C<NUM>-C<NUM>), <NUM>-<NUM> carbon atoms (e.g., C<NUM>-C<NUM>), <NUM>-<NUM> carbon atoms (e.g., C<NUM>-C<NUM>), or <NUM>-<NUM> carbon atoms (e.g., C<NUM>-C<NUM>) as used with respect to any chemical group (e.g., alkyl) referenced herein encompasses and specifically describes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM> carbon atoms, as appropriate, as well as any sub-range thereof (e.g., <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, <NUM>-<NUM> carbon atoms, and/or <NUM>-<NUM> carbon atoms, etc., as appropriate).

The invention provides methods of using heterocyclic compounds, novel heterocyclic compounds, and formulations that are particularly useful for inhibiting corrosion of metallic components in industrial water systems. The methods of the present invention employ compounds of relatively low acute toxicity to aquatic organisms, presenting a more environmentally friendly alternative to existing methods. Applicants have discovered that pyrazole compounds substituted with a heteroatom-containing alkyl group at the <NUM>-position have increased water-solubility. The water-soluble pyrazoles of the present methods provide excellent metal corrosion resistance when added to an aqueous system in contact with a metal surface. While pyrazole provides poor protection against corrosion of copper, (<NUM>-pyrazol-<NUM>-yl)methanol provides excellent copper corrosion resistance (<NUM> mpy vs. <NUM> mpy).

Applicants have also surprisingly and unexpectedly discovered that pyrazole derivatives of the present methods have exemplary stability in the presence of oxidizing halogen compounds. While not wishing to be bound by any particular theory, it is believed that the pyrazole derivatives of the present methods provide a protective film that is impenetrable or essentially impenetrable to common oxidizing halogen compounds. Thus, in certain embodiments, methods of the present invention provide protection against metal corrosion in aqueous systems which employ oxidizing halogen compounds as biocides.

In an embodiment, the invention provides a method for inhibiting corrosion of a metal surface in contact with an aqueous system. The method comprises adding to the aqueous system a compound of formula (I),
<CHM>
wherein X is -OH;.

In certain preferred embodiments, R<NUM> and R<NUM> are hydrogen.

In certain preferred embodiments, R<NUM> is hydrogen.

In certain preferred embodiments, R<NUM> is methyl.

In certain preferred embodiments, R<NUM> is phenyl.

In certain preferred embodiments, R<NUM> is methyl and R<NUM> is methyl.

In certain preferred embodiments, R<NUM> is methyl and R<NUM> is hydrogen.

In certain preferred embodiments, the compound of formula (I) is
<CHM>.

In certain preferred embodiments, the compound of formula (I) is
<CHM>
wherein Me is methyl.

When R<NUM> and R<NUM> form a six-membered aromatic ring, the aromatic ring is optionally substituted and has the following structure:
<CHM>
wherein each of Z is the same or different, and is selected from the group consisting of hydrogen, C<NUM>-C<NUM> alkyl, aryl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, heteroaryl, C<NUM>-C<NUM> cycloalkyl, benzyl, alkylheteroaryl, halogen, halosubstituted alkyl, amino, aminoalkyl, cyano, alkoxy, hydroxyl, thiol, alkylthio, carbonyl, nitro, phosphoryl, phosphonyl, and sulfonyl; X is -OH; Y is -CR<NUM>; m is <NUM>; and n is <NUM>, <NUM>, <NUM>, or <NUM>; or a salt thereof. R<NUM>-R<NUM> are defined as shown above.

The compounds of formula (I) can be a single enantiomer (i.e., (R)-isomer or (S)-isomer), a racemate, or a mixture of enantiomers at any ratio.

The compounds of formula (I) can be prepared by any suitable synthetic chemical method. One method of preparation is a one-step synthesis using commercially available materials. A pyrazole compound undergoes a condensation reaction with an aldehyde to form the <NUM>-substituted pyrazole compound. For example, <NUM>,<NUM>-dimethylpyrazole reacts with formaldehyde to form (<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl) methanol.

In another embodiment (not according to the invention), the disclosure provides a method for inhibiting corrosion of a metal surface in contact with an aqueous system comprising an oxidizing halogen compound. The method comprises adding to the aqueous system a compound of formula (II),
<CHM>.

In the following, embodiments referring to or comprising a compound of formula (II) are not according to the invention:.

In certain preferred embodiments, R<NUM> and R<NUM> are C<NUM>-C<NUM> alkyl.

In certain preferred embodiments, R<NUM> and R<NUM> are methyl.

In certain preferred embodiments, R<NUM> is a halogen.

In certain preferred embodiments, R<NUM> is a chloride.

In certain preferred embodiments, the compound of formula (II) is
<CHM>
wherein Me is methyl.

In certain preferred embodiments, the compound of formula (II) is
<CHM>
wherein Ph is phenyl.

In certain preferred embodiments, R<NUM> is hydrogen. While not wishing to be bound by any particular theory, it is postulated that when R<NUM> is hydrogen, hydrogen-bonding can occur between molecules when added to an aqueous system in contact with a metal surface, thereby resulting in enhanced strength of the corrosion inhibitor protective film on the metal surface. Moreover, compounds of formula (II) where R<NUM> is hydrogen generally have increased water solubility.

The compounds of formulae (I) and (II) may provide corrosion protection for any metal or metal alloy including, but not limited to, copper, iron, silver, steel (e.g., galvanized steel), and aluminum. In certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system in contact with a metal surface comprising copper to inhibit metal corrosion. In certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system in contact with a metal surface comprising a copper alloy to inhibit metal corrosion. In certain embodiments, copper complexes with one or more heteroatoms in a compound of formula (I) or (II). Copper has a wide-range of applications, including use as copper piping and tubing in plumbing and industrial machinery. Copper and copper alloys are well known for their use in cooling water and boiler water systems.

The compounds of formulae (I) and (II) can be used to protect any copper alloy, including bronze, copper-nickel, and brass. Bronze commonly comprises copper and tin, but may comprise other elements including aluminum, manganese, silicon, arsenic, and phosphorus. Brass comprises copper and zinc, and is commonly used in piping in water boiler systems. In certain embodiments, a compound of formula (I) or (II) is added to an aqueous system in contact with a metal surface comprising bronze to inhibit metal corrosion. In certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system in contact with a metal surface comprising brass (e.g., admirality brass) to inhibit metal corrosion. In certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system in contact with a metal surface comprising a copper-nickel alloy to inhibit metal corrosion.

In certain embodiments, a compound of formula (I) or (II) inhibits the corrosion of mild steel. In certain embodiments, a compound of formula (I) or (II) inhibits the corrosion of metal alloys including, but not limited to, galvanized steel, stainless steel, cast iron, nickel, and combinations thereof. While not wishing to be bound by any particular theory, it is postulated that the compounds of formulae (I) and (II) inactivate Cu (II) in solution, preventing the occurrence of galvanic cells on the steel surface. Thus, in certain embodiments, a compound of formula (I) or (II) inhibits pitting corrosion of mild steel.

The corrosion rate provided by compounds of formulae (I) and (II) is not limited. In certain embodiments, a method of inhibiting corrosion comprising using a compound of formula (I) or (II) provides a metal corrosion rate that is acceptable according to industry standards, e.g., about <NUM> mpy or less. In certain preferred embodiments, a compound of formula (I) or (II) provides a metal corrosion rate of about <NUM> mpy or less. Thus, in certain preferred embodiments, a compound of formula (I) or (II) provides a metal corrosion rate of about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, or about <NUM> mpy or less.

While compounds of formulae (I) and (II) can be added to an aqueous system at any dosage rate, the compounds of formulae (I) and (II) are generally added to an aqueous system at a dosage rate of from about <NUM> ppm to about <NUM> ppm. In certain embodiments, a compound of formula (I) or (II) is added to an aqueous system at a dosage rate of from about <NUM> ppm to about <NUM> ppm. Thus, in certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system at a dosage rate of from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, from about <NUM> ppm to about <NUM> ppm, or from about <NUM> ppm to about <NUM> ppm.

An advantage of the present methods is that the compounds of formulae (I) and (II) can be formulated at any pH, including at neutral pH. This is in contrast to many existing methods that employ corrosion inhibitors such as benzotriazole, which require formulation at more hazardous pH levels (e.g., basic pH). Moreover, the compounds of formulae (I) and (II) can be used to inhibit corrosion of metal in an aqueous system having any pH. In certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system having a pH of from about <NUM> to about <NUM>. Thus, in certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system having a pH of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

Another advantage of the present methods is that the compounds of formulae (I) and (II) provide corrosion protection for metal surfaces in the presence of oxidizing halogens. In certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system in contact with a metal surface and inhibits corrosion of the metal surface in the presence of any oxidizing halogen compound. In certain preferred embodiments, a compound of formula (I) or (II) inhibits metal corrosion in the presence of oxidizing halogen compounds including, but not limited to, hypochlorite bleach, chlorine, bromine, hypochlorite, hypobromite, chlorine dioxide, iodine/hypoiodous acid, hypobromous acid, halogenated hydantoins, stabilized versions of hypochlorous or hypobromous acids, or combinations thereof. While not wishing to be bound by any particular theory, it is postulated that the relatively large number of heteroatoms of the compounds of formulae (I) and (II) provide a greater number of sites for bonding to metal surfaces and metal ions, which can provide enhanced corrosion inhibition as compared to many existing corrosion inhibitors. In addition, it is postulated that compounds of formula (I) can form stable films due in part to the formation of a chelation complex with the metal surface.

As discussed above, the compounds of formulae (I) and (II) can reduce the rate of corrosion of copper. In certain embodiments, a compound of formula (I) or (II) surprisingly and unexpectedly provides lower corrosion rates for copper in the presence of oxidizing halogen compounds than compounds commonly used as corrosion inhibitors, such as tolyltriazole. In certain embodiments, a compound of formula (I) or (II) provides a metal corrosion rate in the presence of an oxidizing halogen compound of about <NUM> mpy or less. In certain preferred embodiments, a compound of formula (I) or (II) provides a metal corrosion rate in the presence of an oxidizing halogen compound of about <NUM> mpy or less. Thus, in certain preferred embodiments, a compound of formula (I) or (II) provides a metal corrosion rate in the presence of an oxidizing halogen compound of about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, about <NUM> mpy or less, or about <NUM> mpy or less. In certain preferred embodiments, the metal corrosion rate provided by a compound of formula (I) or (II) is essentially the same in the absence or presence of an oxidizing compound.

In certain preferred embodiments, a compound of formula (I) or (II) inhibits corrosion of copper in the presence of oxidizing halogen compounds including, but not limited to, hypochlorite bleach, chlorine, bromine, hypochlorite, hypobromite, chlorine dioxide, iodine/hypoiodous acid, hypobromous acid, halogenated hydantoins, stabilized versions of hypochlorous or hypobromous acids, or combinations thereof.

In certain embodiments, a compound of formula (I) or (II) inhibits metal corrosion when added to an aqueous system comprising a non-halogen-containing oxidizing biocide including, but not limited to, peroxides (e.g., hydrogen peroxide), persulfates, permanganates, and peracetic acids.

Another advantage of the present methods is that a smaller amount of oxidizing halogen compound is required to maintain low microbial levels because the compounds of formulae (I) and (II) generally has reduced interaction with the oxidizing halogen compound. Furthermore, halogenated azoles that result from the reaction between an azole and oxidizing agent are known to be environmentally undesirable due to their toxicity. Thus, another advantage of the present methods is that the compounds of formulae (I) and (II) are resistant or essentially resistant to halogen attack, and do not lead to the release of halogenated azoles into the environment.

Another advantage of the present invention is that the compounds of formula (I) have enhanced water solubility. In certain embodiments, a compound of formula (I) is water-soluble. In certain preferred embodiments, a compound of formula (I) is soluble in water of from about <NUM>% to about ><NUM>% by weight, at <NUM>. In other words, in certain embodiments, about <NUM>% to about ><NUM>% of a compound of formula (I) dissolves in water at <NUM>. Thus, in certain preferred embodiments, a compound of formula (I) is soluble in water of from about <NUM>% to about ><NUM>%, from about <NUM>% to about ><NUM>%, from about <NUM>% to about ><NUM>%, from about <NUM>% to about ><NUM>%, from about <NUM>% to about ><NUM>%, from about <NUM>% to about ><NUM>%, or from about <NUM>% to about ><NUM>%, at <NUM>. In certain embodiments, ><NUM>% of a compound of formula (I) is soluble in water.

In certain preferred embodiments, the aqueous system is a cooling water system. The cooling water system can be a closed loop cooling water system or an open loop cooling water system. In certain preferred embodiments, a compound of formula (I) or (II) is added to a closed loop cooling water system at a dosage rate of from about <NUM> ppm to about <NUM> ppm. In certain preferred embodiments, a compound of formula (I) or (II) is added to an open loop cooling water system at a dosage rate of from about <NUM> ppm to about <NUM> ppm.

The compounds of formulae (I) and (II) are contacted with a metal surface by any suitable method. In certain embodiments, a solution of a compound of formula (I) or (II) is contacted with a metal surface by immersion, spraying, or other coating techniques. In certain preferred embodiments, a solution of a compound of formula (I) or (II) is introduced into the water of the aqueous system by any conventional method and is fed into the aqueous system on either a periodic or continuous basis.

In certain embodiments, if a compound of formula (I) or (II) is relatively insoluble in water, the compound may be made soluble by forming an organic or inorganic salt of the compound. Thus, in certain embodiments, a compound of formula (I) or (II) is a water-soluble salt. In certain embodiments, a compound of formula (I) or (II) is added as a solution in a water-miscible co-solvent including, but not limited to, acetone, methanol, ethanol, propanol, formic acid, formamide, propylene glycol, or ethylene glycol. In certain embodiments, low molecular weight polyethylene glycol, polypropylene glycol, or a surfactant is used to increase the solubility of a compound of formula (I) or (II). In certain embodiments, a co-solvent is used to achieve maximum solubility of a compound of formula (I) or (II) in the aqueous system.

In another embodiment, the invention provides a formulation for inhibiting corrosion of a metal surface in contact with an aqueous system. The formulation comprises a compound of formula (I) or (II), a phosphoric acid, and a phosphinosuccinic oligomer. In a certain preferred embodiments, the phosphoric acid is orthophosphoric acid (i.e., phosphoric acid). In certain embodiments, the phosphinosuccinic oligomer is selected from the phosphinosuccinic oligomers as disclosed in <CIT>, which is hereby incorporated by reference.

In certain preferred embodiments, the formulation comprises a compound of formula (I) wherein X is selected from the group consisting of -OH, -NH<NUM>, -SH, and halogen; Y is selected from the group consisting of -CR<NUM> and nitrogen; R<NUM> and R<NUM> form a six-membered aromatic ring, or each of R<NUM> and R<NUM> is the same or different and selected from the group consisting of hydrogen, aryl, heteroaryl, C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, C<NUM>-C<NUM> cycloalkyl, benzyl, alkylheteroaryl, halogen, halosubstituted alkyl, amino, aminoalkyl, cyano, hydroxyl, alkoxy, thiol, alkylthio, carbonyl, nitro, phosphoryl, phosphonyl, and sulfonyl; R<NUM> is selected from the group consisting of hydrogen, aryl, heteroaryl, C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, C<NUM>-C<NUM> cycloalkyl, benzyl, alkylheteroaryl, halogen, halosubstituted alkyl, amino, aminoalkyl, cyano, hydroxyl, alkoxy, thiol, alkylthio, carbonyl, nitro, phosphoryl, phosphonyl, and sulfonyl; R<NUM> is selected from the group consisting of hydrogen, aryl, heteroaryl, C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, C<NUM>-C<NUM> cycloalkyl, benzyl, alkylheteroaryl, halogen, halosubstituted alkyl, amino, aminoalkyl, cyano, hydroxyl, alkoxy, thiol, alkylthio, carbonyl, nitro, phosphoryl, phosphonyl, and sulfonyl; and m is an integer of from <NUM> to <NUM>; or a salt thereof.

In certain preferred embodiments, the formulation comprises a compound of formula (II) wherein each of R<NUM>, R<NUM>, and R<NUM> is the same or different and selected from the group consisting of hydrogen, aryl, heteroaryl, C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, C<NUM>-C<NUM> cycloalkyl, benzyl, alkylheteroaryl, halogen, halosubstituted alkyl, amino, aminoalkyl, cyano, hydroxyl, alkoxy, thiol, alkylthio, carbonyl, nitro, phosphoryl, phosphonyl, and sulfonyl; and R<NUM> is selected from the group consisting of hydrogen, deuterium, C<NUM>-C<NUM> alkyl, aryl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, heteroaryl, C<NUM>-C<NUM> cycloalkyl, benzyl, alkylheteroaryl, halogen, hydroxyl, and carbonyl; or a salt thereof.

In certain embodiments, the formulation further comprises a fluorescent organic compound. In certain preferred embodiments, the fluorescent organic compound is selected from the group consisting of Rhodamine, a derivative of Rhodamine, an acridine dye, fluorescein, a derivative of fluorescein, and combinations thereof. In certain embodiments, the formulation further comprises a fluorescent tagged polymer.

In certain embodiments, the formulation has a pH of from about <NUM> to about <NUM>. Thus, in certain embodiments, the formulation has a pH of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. In certain embodiments, the formulation has a pH of from about <NUM> to about <NUM>. Thus, in certain embodiments, the formulation has a pH of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

In another embodiment, the invention provides a compound of formula (I):
<CHM>
wherein X is -OH;.

In certain preferred embodiments, R<NUM> is aryl or heteroaryl.

Those skilled in the art will appreciate that compounds of formula (I) or (II) can be added to an aqueous system alone or in combination with other corrosion inhibitors or treatment chemicals. Multiple corrosion inhibitors can be dosed as a combined corrosion inhibitor formulation or each corrosion inhibitor can be added separately, including two or more compounds of formula (I) and/or formula (II). Moreover, a compound of formula (I) or (II) can be added to an aqueous system in combination with a variety of additional corrosion inhibitors including, but not limited to, triazoles, benzotriazoles (e.g., benzotriazole or tolyltriazole), benzimidazoles, orthophosphate, polyphosphates, phosphonates, molybdates, silicates, oximes, and nitrites. The compounds of formulae (I) and (II) also can be added to an aqueous system in combination with a variety of additional additives, such as treatment polymers, anti-microbial agents, anti-scaling agents, colorants, fillers, buffers, surfactants, viscosity modifiers, chelating agents, dispersants, deodorants, masking agents, oxygen scavengers, indicator dyes, and combinations thereof.

The compounds of formulae (I) and (II) can be added to an aqueous system in any form. In certain embodiments, a compound of formula (I) or (II) is added to an aqueous system as a dried solid. In certain embodiments, a compound of formula (I) or (II) is added to an aqueous system as a solution in a co-solvent miscible with water. In certain preferred embodiments, a compound of formula (I) or (II) is added to an aqueous system as an aqueous solution.

In certain embodiments, the present invention provides methods of low aquatic toxicity. In certain embodiments, a compound of formulae (I) and (II) has reduced toxicity. In certain embodiments, a compound of formula (I) or (II) has a LC<NUM> of greater than <NUM>/L. In certain embodiments, a compound of formula (I) or (II) has a LC<NUM> of greater than <NUM>/L in a Oncorhynchus mykiss aquatic toxicity test.

In certain embodiments, a compound of formula (I) is added to a laundry system or a warewashing system.

In certain embodiments, a compound of formula (I) or (II) is added to an aqueous system that recirculates water. In certain embodiments, a compound of formula (I) or (II) is added to an aqueous system that has stagnant water.

The following examples further illustrate the invention.

This Example illustrates a method of synthesizing compounds of formulae (I) and (II).

General Chemistry Methods. The reactions were performed under positive pressure of nitrogen with oven-dried glassware. Pyrazole and <NUM>,<NUM>-dimethylpyrazole were purchased from TCI America. Formaldehyde, acetaldehyde, styrene oxide, N-succinimide, THF, and methanol were purchased from Sigma-Aldrich (St. Louis, MO).

Synthesis of (<NUM>-pyrazol-<NUM>-yl)methanol. A roundbottom flask comprising pyrazole (<NUM> mmol, <NUM>) and methanol (about <NUM>) was charged with formaldehyde (<NUM>, <NUM>% aq. The reaction mixture was stirred at <NUM> for <NUM> hours to give a homogenous solution. The solvent was removed under reduced pressure and dried in vacuo for <NUM> hours, yielding the title compound (<NUM>, <NUM>%).

Synthesis of <NUM>-(<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl)ethan-<NUM>-ol. A roundbottom flask comprising <NUM>,<NUM>-dimethylpyrazole (<NUM> mmol, <NUM>) and THF (<NUM>) was charged with acetaldehyde (<NUM> mmol, <NUM>). The reaction mixture was stirred at <NUM> for <NUM> hours. The solvent was removed under reduced pressure and the solid was dried in vacuo, yielding the title compound (<NUM>, <NUM>% yield).

Synthesis of (<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl)(phenyl)methanol. A roundbottom flask comprising <NUM>,<NUM>-dimethylpyrazole (<NUM> mmol, <NUM>) and xylene (<NUM>) was charged with styrene oxide (<NUM> mmol, <NUM>). The reaction mixture was stirred and refluxed at <NUM> for <NUM> hours. The reaction mixture was cooled to room temperature. The solid was collected by filtration, washed with xylene, and dried at <NUM>° C, yielding the title compound (<NUM>, <NUM>% yield).

Synthesis of <NUM>-chloro-<NUM>,<NUM>-dimethyl-<NUM>-pyrazole. A roundbottom flask comprising <NUM>,<NUM>-dimethylpyrazole (<NUM> mmol, <NUM>) and N-succinimide (<NUM> mmol, <NUM>) was charged with chloroform (<NUM>). The reaction mixture was stirred at <NUM> for <NUM> hours. The mixture was partitioned between chloroform and water. The organic phase was washed with water and brine and dried over Na<NUM>SO<NUM>. The mixture was filtered and solvent was removed in vacuo, yielding the title compound (<NUM>, <NUM>% yield).

This Example illustrates the corrosion rate of copper.

The corrosion rate of copper in the presence of (<NUM>-pyrazol-<NUM>-yl)methanol, (<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl)methanol, (<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl)(phenyl)methanol, <NUM>-(<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl)ethan-<NUM>-ol, <NUM>-(<NUM>-pyrazol-<NUM>-yl)ethan-<NUM>-ol, <NUM>-phenyl-<NUM>-pyrazole, <NUM>-chloro-<NUM>,<NUM>-dimethyl-<NUM>-pyrazole, and <NUM>,<NUM>-dimethylpyrazole was determined using linear polarization resistance measurements. In addition, the corrosion rate of copper in the presence of pyrazole, <NUM>-ethyl-<NUM>-pyrazole, and tolyltriazole was determined using linear polarization resistance measurements. (<NUM>-Pyrazol-<NUM>-yl)methanol, (<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl)methanol, (<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl)(phenyl)methanol, <NUM>-chloro-<NUM>,<NUM>-dimethyl-<NUM>-pyrazole, and <NUM>-(<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl)ethan-<NUM>-ol were prepared by Applicants. Pyrazole, <NUM>,<NUM>-dimethylpyrazole, <NUM>-(<NUM>-pyrazol-<NUM>-yl)ethan-<NUM>-ol, and <NUM>-ethyl-<NUM>-pyrazole were purchased from TCI America. <NUM>-Phenyl-<NUM>-pyrazole and tolyltriazole were purchased from Sigma-Aldrich (St. Louis, Mo).

For each experiment, cylindrical copper coupons pre-polished using SIC <NUM> paper and fitted on a Pine rotator were immersed in a solution of corrosion inhibitor. The test solution comprised <NUM> ppm calcium, <NUM> ppm magnesium, <NUM> ppm chloride, <NUM> ppm sulfate, and <NUM> ppm alkalinity, as CaCO<NUM>. The pH of the test water was maintained at <NUM> using carbon dioxide, and the water temperature was maintained at <NUM> throughout the experiment.

The copper samples were immersed in <NUM> liter electrochemical cells comprising a <NUM> ppm inhibitor solution, and the Rp (polarization resistance) was recorded over a <NUM> hour period. The analysis was conducted using the following testing conditions: Initial E: -<NUM>. 02V; Final E: +<NUM>. 02V; Scan rate: <NUM> mV/s; Sample period: <NUM> second; Repeat time: <NUM> minutes; Sample area: <NUM><NUM>; Density: <NUM>/cm<NUM>; Copper Eq. Weight: <NUM>; and Initial delay: <NUM> seconds.

Next, the copper samples were exposed to <NUM> ppm FRC by adding a few drops of <NUM>% bleach solution to the electrolyte solution. After the FRC reached <NUM> ppm, the copper samples were analyzed. Throughout the analysis, the bleach solution was added intermittently to maintain the FRC at <NUM> ppm. The Rp in the absence and presence of bleach was collected and analyzed, and the average corrosion rate was calculated and recorded in Table <NUM>. Corrosion rates were calculated in mils per year (mpy). <FIG> display data plots for compounds <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

As shown in Table <NUM> and <FIG>, compounds <NUM>-<NUM> provide copper corrosion rates less than <NUM> mpy. In particular, compounds <NUM>-<NUM> greatly decrease the rate of copper corrosion. The data suggests that alcohol substitution at the <NUM>-position of the pyrazole provides an overall decrease in the rate of copper corrosion. For example, it was surprisingly and unexpectedly discovered that (<NUM>-pyrazol-<NUM>-yl)methanol (compound <NUM>) provides greater corrosion protection than pyrazole (compound <NUM>). In addition, (<NUM>,<NUM>-dimethyl-<NUM>-pyrazol-<NUM>-yl) methanol (compound <NUM>) provides a lower corrosion rate than <NUM>,<NUM>-dimethylpyrazole (compound <NUM>). Moreover, the data suggests that substitution with secondary alcohols can provide enhanced corrosion inhibition (e.g., compounds <NUM> and <NUM> vs. compound <NUM>).

Upon the addition of bleach, it was found that compounds of the present method provide good protection against copper corrosion. The corrosion rate of copper in the presence of compounds <NUM>-<NUM>, <NUM>, and <NUM> remained well below <NUM> mpy in the presence of bleach, and provide greater corrosion protection than pyrazole and tolyltriazole.

This Example illustrates that a method of an embodiment of the present invention can reduce the rate of copper corrosion. Moreover, this Example illustrates that a method of an embodiment of the present invention can provide greater corrosion resistance in the presence of an oxidizing halogen than commonly used corrosion inhibitors such as tolyltriazole.

This Example illustrates the solubility of compounds of formulae (I) and (II) at various pH levels.

Solutions comprising (<NUM>-pyrazol-<NUM>-yl)methanol and <NUM>,<NUM>-dimethylpyrazole at various pH levels were prepared by dissolving the corresponding pyrazole (<NUM> grams) in deionized water (<NUM> grams). The solutions were adjusted to the desired pH by adding dilute sulfuric acid or aqueous sodium hydroxide (<NUM> N). The turbidity of each solution was measured using a HACH 2100Q Portable Turbidimeter.

As shown in <FIG> and <FIG>, the measured turbidity for all analyzed solutions was less than <NUM> NTU, confirming that (<NUM>-pyrazol-<NUM>-yl)methanol and <NUM>,<NUM>-dimethylpyrazole are water soluble and can be formulated at a wide-range of pH levels.

This Example illustrates the aquatic toxicity of a corrosion inhibitor.

The aquatic toxicity of (<NUM>-pyrazol-<NUM>-yl)methanol toward a variety of species was analyzed. The toxicity data is listed in Table <NUM>. (<NUM>-pyrazol-<NUM>-yl)methanol had lower aquatic toxicity than many commonly used corrosion inhibitors. For example, (<NUM>-pyrazol-<NUM>-yl)methanol had a LC<NUM> of ><NUM> in the presence of Oncorhynchus mykiss.

Claim 1:
A method for inhibiting corrosion of a metal surface in contact with an aqueous system, the method comprising adding to the aqueous system a compound of formula (I),
<CHM>
wherein X is -OH;
Y is -CR<NUM>;
R<NUM> and R<NUM> form a six-membered aromatic ring or each of R<NUM> and R<NUM> is the same or different and selected from the group consisting of hydrogen, aryl, heteroaryl, C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, C<NUM>-C<NUM> cycloalkyl, benzyl, alkylheteroaryl, ; R<NUM> is selected from the group consisting of hydrogen, aryl, heteroaryl, C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl, C<NUM>-C<NUM> cycloalkyl, benzyl, alkylheteroaryl,;
R<NUM> is selected from the group consisting of hydrogen, C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkenyl, C<NUM>-C<NUM> alkynyl; and
m is <NUM>; or
a salt thereof.