Corrosion control for aqueous systems using passivators and hydroxycarboxylic acids

Abstract

Methods and compositions for inhibiting corrosion of a corrosive metal surface in contact with a water stream in an aqueous system. The method includes introducing a treatment composition into the water stream, the treatment composition including a combination of a passivating agent and a hydroxycarboxylic acid promoter.

Description

Technical Field

[0001] This application claims the benefit of priority of Provisional Application No. 63 / 346,134, filed May 26, 2022. The entire content of the prior application is hereby incorporated by reference in its entirety.

[0002] This application is directed to methods and compositions for treating corrosion inhibitors in aqueous systems, such as those used in industrial processes.

Background Art

[0003] Corrosion in industrial water systems is a serious problem. It causes undesirable consequences including loss of heat transfer, increased cleaning frequency, equipment repair and replacement, shutdowns, environmental problems, and increased resources and costs associated therewith.

[0004] Treatment of corrosion in aqueous systems is typically achieved by the continuous application of various corrosion inhibitors in water, including, for example, phosphates, polymers, chromates, zinc, molybdates, nitrates, and combinations thereof. These inhibitors act on the principle of shifting the electrochemical corrosion potential of the corroding metal in a positive direction showing a delay in the anodic process (anodic control) or moving it in a negative direction mainly showing a delay in the cathodic process (cathodic control). Corrosion inhibitors act on the cathode and / or anode of the corrosion cell.

[0005] Common corrosion inhibitors include salts such as orthophosphates, polyphosphates, phosphonates, zinc, molybdates, silicates, nitrates, etc. Among these corrosion inhibitors, phosphorus-based corrosion inhibitors have good cost-effectiveness and performance, and are widely used for carbon steel corrosion control in cooling water applications. However, cooling water is ultimately discharged into surface water, and there are concerns about the environmental impact of phosphorus due to algal blooms. Although somewhat effective, there are several problems associated with the chemical properties of these zinc and phosphate salts as corrosion prevention treatments: (1) These chemical properties do not form a very robust film, and a slight change in the environment (e.g., a decrease in pH) may break the film, and corrosion products may accumulate before the film can be restored by normal treatment. (2) Zinc and phosphates tend to precipitate on the heat transfer surface when applied at levels necessary to form a robust passive film, and (3) The release of chemicals such as phosphates and zinc is often restricted by environmental regulations. Industry may face significant difficulties in discharging these chemicals at higher levels. In this regard, regulatory requirements regarding phosphorus continue to become more stringent, requiring a cooling water corrosion inhibitor product solution that can provide less than 2 ppm of phosphorus (typically less than 1 ppm or 0.5 - 1 ppm) in its discharge stream.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Tin compounds as corrosion inhibitors have been the subject of several experiments in industrial water systems. Certain formulations of stannous salts are uniquely suitable for protecting various steels in water by forming a robust protective layer on the metal surface at an economic treatment level. Unlike phosphate and zinc-based passivation treatments, these stannous salt formulations can be applied at effective levels without the risk of contaminating the heat transfer surface. Furthermore, stannous salt passivation formulations pose far less risk to the environment than the chemistry of chromates, zinc, and phosphates previously used for corrosion prevention.

[0008] A method of using a tin corrosion inhibitor in combination with a hydroxycarboxylic acid promoter has also been proposed, as described in Patent Document 1 by Kalakodimi (Barton) et al., which is hereby incorporated by reference in its entirety. These methods enhance the effectiveness of tin-based corrosion inhibitors while allowing for lower concentrations of inhibitors and promoters.

[0009] The implementation of conventional corrosion prevention using tin compounds has not been able to effectively address the problem of maintaining an effective amount of tin(II) in solution long enough to form a protective film on the surface of the corrosive metal without losing the active form of tin(II), presumably due to bulk phase oxidation and precipitation to tin(IV). Furthermore, the use of organic compounds as corrosion inhibitors is challenging and often prohibited due to volume and cost requirements. Additionally, the method of using a tin corrosion inhibitor in combination with a hydroxycarboxylic acid promoter leaves room for improvement in terms of efficiency and cost. These problems and others are addressed by the present disclosure.

[0010] The object of the present disclosure is to provide a method for the improved and effective use of a high-performance non-phosphorus chemical corrosion inhibition treatment program that can be used in cooling water applications to prevent the corrosion of carbon steel. The treatment program includes a synergistic combination of a passivator, such as a salt of a polyvalent metal and a hydroxycarboxylic acid. The treatment program may further include a dispersant polymer that produces additional synergistic effects. These treatment programs are more environmentally friendly than current common phosphorus corrosion inhibitors and are more effective and synergistic than current first tin and hydroxycarboxylic acid treatments.

Means for Solving the Problems

[0011] In the first embodiment, a method for suppressing corrosion of a corrosive metal surface in contact with an aqueous water flow is provided. This method includes introducing a treatment composition containing a combination of a passivating agent and a hydroxycarboxylic acid accelerator into the water flow, and the hydroxycarboxylic acid accelerator has a carboxylic acid group and a hydroxyl group bonded to a carbon atom adjacent to the carboxylic acid group. The treatment composition is introduced such that the concentration of the combination of the passivating agent is in the range of 0.1 to 10 ppm and the concentration of the accelerator in the water flow is in the range of 2 ppm to 50 ppm.

[0012] In the second embodiment, a method for suppressing corrosion of a corrosive metal surface in contact with an aqueous water flow is provided. This method includes introducing a treatment composition containing a combination of a polyvalent metal salt and a hydroxycarboxylic acid accelerator into the water flow, and the hydroxycarboxylic acid accelerator has a carboxylic acid group and a hydroxyl group bonded to a carbon atom adjacent to the carboxylic acid group. The treatment composition is introduced such that the concentration of the combination of the polyvalent metal salt is in the range of 0.1 to 10 ppm and the concentration of the accelerator in the water flow is in the range of 2 ppm to 50 ppm.

[0013] In another embodiment, a chemical treatment composition for use in suppressing corrosion of a corrosive metal surface in contact with an aqueous water flow is provided. This composition includes a combination of a polyvalent metal salt and a hydroxycarboxylic acid accelerator, and the hydroxycarboxylic acid accelerator has a carboxylic acid group and a hydroxyl group bonded to a carbon atom adjacent to the carboxylic acid group. The concentration of the combination of the polyvalent metal salt is in the range of 0.1 to 10 ppm, and the concentration of the accelerator in the water flow is in the range of 2 ppm to 50 ppm.

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

[0016] The following will be described in detail.

[0017] [Summary] Embodiments of the disclosed methods and compositions are applicable to the discovery of improved corrosion prevention and are applicable to water systems including, but not limited to, cooling towers, water distribution systems, boilers, pasteurizers, water and brine transport pipelines, storage tanks, and the like. Embodiments of the present methods and compositions are particularly useful in cooling towers in industrial water processes. By treating an aqueous system with a combination of a passivating agent and a hydroxycarboxylic acid accelerator compound, improved corrosion prevention can be achieved at a lower cost and with less environmental impact. The disclosed embodiments form a very robust and persistent inhibitor film on the surface of corrosive metals by treating with a combination of a passivating agent and an accelerator compound.

[0018] The disclosed treatment methods result in excellent corrosion inhibition and a significant reduction in the amounts of passivating and accelerator agents required, which is beneficial to the environment and reduces the cost of treatment. The method provides a more economical treatment of large-volume systems, including, for example, once-through applications and other systems where water consumption and losses pose significant challenges to the dosages and controls using conventional corrosion protection treatments. The method also significantly reduces the amount of passivating and / or corrosion inhibitor agents required to protect the treated system by reducing consumption losses associated with oxidation and water discharge from the system.

[0019] The above reasons are believed to be that a synergistic combination of a passivator and a hydroxycarboxylic acid was used in the embodiments. Further, combining passivators tends to result in more complete passivation. The disclosed embodiments are also beneficial when the effluent from the treated system is used in a manner or for a purpose such that conventional inhibitors are considered contaminants or are considered harmful to the intended use. Such treatments are more resistant to overdosage compared to conventional zinc or phosphate that rely on high-volume polymer dispersants to inhibit the formation of undesirable deposits, as well as current tin corrosion inhibitors and hydroxycarboxylic acid programs.

[0020] [Passivator containing accelerator] The combination of passivators according to the embodiments can include any two salts of a polyvalent metal that can form a stable metal oxide resistant to dissolution under the conditions in the target system. Preferably, the metal may be selected from the group consisting of manganese, tungstate, aluminum, and tin. The passivators according to the embodiments include, but are not limited to, esters of the disclosed metal salts, such as phosphate esters, and may also include non-metal salts.

[0021] Preferably, it contains tin as the first metal salt. The disclosed embodiments may use tin as a corrosion inhibitor. Tin particularly suitable for use with the disclosed methods includes tin(II) compounds. Tin(II) is more soluble in aqueous solution than metal ions in higher oxidation states such as tin(IV). For such metals, species in a lower oxidation state can be introduced into the treatment system, for example, by directly introducing stannous salts or by feeding a concentrated solution to the treatment system. Corrosion inhibitors are consumed in various ways within the treated system. These consumption pathways can be classified as system demand and surface demand. The sum of system demand and surface demand includes the total inhibitor demand.

[0022] Tin (II) may be provided as a stannous salt selected from the group consisting of stannous sulfate, stannous bromide, stannous chloride, stannous oxide, stannous phosphate, stannous pyrophosphate, and stannous tetrafluoroborate. Other reactive metal salts, such as zirconium and / or titanium metal salts, may also be used in the treatment method according to the present disclosure.

[0023] The concentration of the first metal salt, such as tin, in the water stream may be present in the aqueous system in a relatively small amount, for example, in the range of 0.01 ppm to 3 ppm, 0.05 ppm to 2 ppm, 0.1 ppm to 1.25 ppm, or 0.5 ppm to 0.75 ppm.

[0024] Preferably, it contains aluminum as the second metal salt. Aluminum can function as an auxiliary corrosion inhibitor or a secondary accelerator (secondary to the hydroxycarboxylic acid accelerator). Without being bound by theory, the disclosed treatment is believed to function by at least one of removing aluminum silicate from the water stream and forming an aluminum silicate film on the surface. In conventional water treatment systems, aluminum was simply used as a coagulant and not considered a corrosion inhibitor. The inventors have unexpectedly found that combining aluminum with other polyvalent metals and hydroxycarboxylic acids provides surprisingly beneficial corrosion inhibition. In embodiments, the aluminum salt may be an inorganic or organic aluminum salt. Examples of inorganic aluminum salts may include, but are not limited to, aluminum chloride, polyaluminum chloride, aluminum nitrate, and aluminum sulfate. Examples of organic aluminum salts may include, but are not limited to, aluminum citrate and aluminum gluconate. In a preferred embodiment, the aluminum salt may be aluminum chloride.

[0025] The concentration of the second metal salt, such as aluminum, in the water stream may be present in the water system in a relatively small amount, for example, in the range of 0.01 ppm to 3 ppm, 0.05 ppm to 2 ppm, 0.1 ppm to 1.25 ppm, 0.25 to 0.75 ppm, or 0.3 ppm to 0.5 ppm.

[0026] According to an embodiment, the synergistic combination of the first metal salt and the second metal salt results in a significantly lower total amount of metal salts than was previously possible. For example, the total amount of the first metal salt, such as tin, and the second metal salt, such as aluminum, may be present in the water system in the range of 0.01 ppm to 50 ppm, 0.05 ppm to 20 ppm, 0.1 ppm to 10 ppm, 0.1 ppm to 5 ppm, 0.25 to 1.5 ppm, or 0.25 to 1.5 ppm.

[0027] Accelerator compounds particularly suitable for use in embodiments are hydroxycarboxylic acids. Hydroxycarboxylic acids are carboxylic acids substituted with hydroxyl groups on adjacent carbon moieties. Hydroxycarboxylic acids are well-known organic compounds applied to various uses. Examples include, but are not limited to, tartaric acid, glucaric acid, glucoheptonic acid, maleic acid, gluconic acid, and polyaspartic acid. In an embodiment, the accelerator may be glucaric acid. In an embodiment, the accelerator may be a polymeric hydroxycarboxylic acid.

[0028] The concentration of the hydroxycarboxylic acid accelerator in the water stream may be present in the water system in the range of 0.1 ppm to 100 ppm, 0.5 ppm to 50 ppm, 2 ppm to 50 ppm, 5 ppm to 20 ppm, or 7.5 ppm to 20 ppm.

[0029] In an embodiment, the ratio of the concentration of the combination of metal salts in the water stream, expressed in ppm, to the concentration of the accelerator in the water stream, expressed in ppm, may be in the range of 0.001 to 0.4, 0.01 to 0.2666, or 0.05 to 0.1666. This ratio may also be in the range of 0.00025 to 0.4, 0.00033 to 0.2666, or 0.005 to 0.1666.

[0030] In an embodiment, the ratio of the concentration of the first metal salt in the water stream expressed in ppm to the concentration of the accelerator in the water stream expressed in ppm may be in the range of 0.001 to 0.4, 0.01 to 0.2666, or 0.05 to 0.1666. This ratio can also be in the range of 0.00025 to 0.4, 0.00033 to 0.2666, or 0.005 to 0.1666.

[0031] In an embodiment, the ratio of the concentration of the second metal salt in the water stream expressed in ppm to the concentration of the accelerator in the water stream expressed in ppm may be in the range of 0.001 to 0.4, 0.01 to 0.2666, or 0.05 to 0.1666. This ratio can also be in the range of 0.00025 to 0.4, 0.00033 to 0.2666, or 0.005 to 0.1666.

[0032] In an embodiment, the ratio of the concentration of the corrosion inhibitor in the water stream expressed in ppm to the concentration of the metal salt in the water stream expressed in ppm may be in the range of 0.001 to 10, 0.01 to 1, or 0.75 to 1.25. This ratio can also be in the range of 0.5 to 1.5, 0.75 to 1, or 0.8 to 1.1.

[0033] The concentration of the combination of the metal salt and the accelerator achieved during the corrosion inhibitor treatment can be selected to exceed the baseline system requirements, thereby ensuring that a portion of the supplied inhibitor is available to treat vulnerable metal surfaces.

[0034] In many scenarios, the system requirements can be due to the presence of oxygen, halogens, other oxidizing species, and other components in the aqueous system that can react with or remove the inhibitor, thereby inactivating or consuming the inhibitor. For example, in the first tin salt treatment, the oxidizing species can convert the preferred tin(II) stannous ions, (at least in the process water stream) to tin(IV) stannate ions with little effect. System demand also includes, for example, inhibitor loss associated with bulk water loss through other emissions from the blown and / or treated system.

[0035] Surface demand is the consumption of the inhibitor due to the interaction between the inhibitor and the reactive metal surface. As the inhibitor forms a protective film or layer on the metal surface that was vulnerable to corrosion, the surface demand decreases. Once all the wet surfaces are properly protected, the surface demand is nil or almost nil. As the surface demand amount decreases to a value close to zero, the required amount of additional corrosion inhibitor can substantially decrease or even end for a period without compromising the effectiveness of corrosion prevention.

[0036] The first tin compound undergoes oxidation on the vulnerable metal surface or the surface requiring corrosion protection to form an insoluble protective film. These metal surfaces can also react with the first tin compound to form a metal-tin complex, which also forms a protective film on the metal surface. Without being bound by theory, the first tin inhibitor applied according to the disclosed method appears to form a protective film on the reactive metal by at least three mechanisms. The first mechanism involves forming an insoluble stannous hydroxide layer under alkaline conditions. This stannous hydroxide further oxidizes to form an even more insoluble stannate oxide layer, resulting in a protective film that is resistant to dissolution from the surface even in the absence of the first tin salt in the process water. The second mechanism is achieved under acidic conditions or in the presence of surface oxidants such as ferric ions or cupric ions, whereby the first tin salt can be directly oxidized to highly insoluble stannates. These stannates then precipitate on the metal surface to form a protective layer, providing the desired corrosion prevention function. The third mechanism is achieved under alkaline conditions, whereby the metal oxides present are reduced to a more stable reduced form that incorporates insoluble tin salts into the hybrid film.

[0037] In each of the above mechanisms, the final result is a tin (IV) stannate film formed on or at the metal surface. The insolubility and stability of the resulting stannate film provide an effective barrier against corrosion for a limited period, even when no additional tin species are provided in the aqueous component of the system being treated. The tin (IV) film structure has been confirmed by X-ray photoelectron spectroscopy (XPS) analysis of the metal surface. XPS reveals the presence of the tin (IV) film on the metal coupon surface.

[0038] [Treatment Methods and Compositions] In a first embodiment, a method for inhibiting corrosion of a corrosive metal surface in contact with an aqueous water stream is provided. The corrosive metal surface may be a metal or alloy selected from the group consisting of ferrous metals, aluminum metals, brass, copper-containing alloys, and galvanized steel. The method includes introducing a treatment composition comprising a combination of a polyvalent metal salt and a hydroxycarboxylic acid accelerator into the water stream over a first period.

[0039] The combination of the polyvalent metal salt and the hydroxycarboxylic acid accelerator in the composite treatment supply provides a synergistic anti-corrosion effect. For example, the combination treatment according to the embodiment provides an unexpectedly high corrosion prevention rate using a relatively small effective amount of the metal salt and the hydroxycarboxylic acid accelerator that would not be effective in a single treatment regime otherwise. Without intending to be bound by theory, it is believed that the accelerator compound is achieving two processes: (1) forming an anti-corrosion film on the metal surface, and (2) effectively chelating the metal active state, such as tin (II), for a longer time than previously known, thereby enabling tin (II) to react with the metal surface and form an elastic tin (IV) film. Although the mechanism is unknown, hydroxycarboxylic acid is thought to promote the active state of tin (II) by acting as a chelating agent.

[0040] The method and manner of injecting the treatment agent into the water stream are not particularly limited by the present disclosure. The treatment agent can be injected into the water system, for example, in a cooling tower or at any suitable location in the water stream in the water system. Methods for injecting the treatment agent, including controlling the injection flow, can include, as understood by those skilled in the art, a multi-valve system and the like. Furthermore, the control of the treatment agent while it is within the system is not particularly limited. The injection control, including frequency, duration, concentration, dosage, type of administration, etc., can be manually or automatically controlled, for example, via a computer-executable medium such as an algorithm or a CPU. These controls can further be implemented using data and history-driven learning capabilities and feedback loops to automatically adapt the treatment plan to the system and metal surface environmental conditions. The treatment can be continuous, intermittent, or periodic. The metal salt can be added to the water stream separately from the hydroxycarboxylic acid promoter, or each can be added separately.

[0041] The treatment remains within the system for all cycles (i.e., via a heat exchanger, etc.) or several cycles and is then gradually removed from the system with the process water in the system, for example, in the case of cooling water, through known blowdown removal techniques. The metal salt and / or corrosion inhibitor are consumed in various ways within the treated system. These consumption paths can be classified into system demand and surface demand. The system demand and surface demand together include the total demand for the salt or inhibitor.

[0042] The amount of the treatment composition can be applied based on the system demand and surface demand of the inhibitor. Controlling the amount of the treatment composition can utilize several parameters related to surface and system demands, including, for example, the concentration of corrosion products in water or the demand of the metal surface for reducing species. Other parameters such as online corrosion rate and / or oxidation-reduction potential (ORP) may also be used to control the treatment frequency or to monitor system performance.

[0043] In addition to metal salts, the treatment agent may include many other materials. For example, the treatment agent may include at least one of citric acid, benzotriazole, and (Z)-2-butenedioic acid, a bicarbonate for increasing the alkalinity of the solution, a polymer dispersant such as 2-acrylamido-2-methylpropanesulfonic acid (AMPS) for suppressing mud or dirt, and polymaleic acid (PMA) for suppressing scaling. The treatment agent may include, for example, ChemTreat FlexPro®. Examples include CL5632 (phosphorus-free and zinc-free corrosion treatment agent) manufactured by ChemTreat.

[0044] The treatment composition may be administered by shot, service dosing, or continuous supply. The treatment administration period can range from 5 minutes to 2 days, or more preferably from 10 minutes to 24 hours in the case of shot dosing. The service dosing intervals may be substantially the same or shorter depending on the target concentration requirements in the water stream. Similarly, the continuous supply treatment intervals depend on the system demand as described herein.

[0045] In the initial stage of treatment in a system having existing corrosion and / or exposed metal surfaces, the total demand for metal salts or inhibitors is high but decreases as the metal surface is treated by the treatment. The treatment end point is reached when all surfaces are treated and only the demand of the system (non-metal surfaces) remains. Once effective treatment is achieved using the treatment period, the system can be operated over a long period without the need to further add metal salts or with a substantial reduction in the metal salt level.

[0046] In another embodiment, after a period in which a substantially reduced level of the combination of metal salts is added, the method may include introducing the treatment composition into the water stream over a second period, during which a second concentration of the combination of metal salts in the water stream may be substantially the same as or less than the initial concentration of the combination of metal salts. During the second period, a second concentration of the accelerator in the water stream may be substantially the same as or less than the first concentration of the accelerator. The duration of the second period is not particularly limited and may be shorter or longer than the first period depending on system requirements.

[0047] In embodiments using such intermittent or periodic treatments, the frequency or time between treatments is not particularly limited. The frequency may be about 2 - 30 days, or preferably 3 - 7 days. More preferably, the time between treatments is about 7 days. In some systems, it may be beneficial to maintain a certain continuous level of the active corrosion inhibitor in the water process stream after the treatment period. Maintaining a continuous low to very low level of the active metal salt after treatment agent dosing can reduce the frequency with which subsequent treatment agents are required. The duration, timing and concentration of the treatment dosage can vary depending on the requirements of the system as described herein.

[0048] As will be appreciated, the frequency of combination supply, the concentration of the metal salts and the accelerator are necessarily a function of the system being treated and can be set and / or adjusted empirically based on test or historical data. In embodiments, the concentration of the metal salt achieved during treatment is selected to exceed the baseline system requirements, thereby ensuring that a portion of the metal salt supplied is available to treat vulnerable metal surfaces.

[0049] The success of the treatment can be evaluated by monitoring the total inhibitor requirement that would be essentially equal to the system requirement when the surface requirement is effectively suppressed or eliminated. System demand can be measured indirectly by monitoring parameters such as ORP and oxygenation level. Thus, according to one embodiment, the treatment method may further include measuring and monitoring the properties of the metal surface or water stream during or after treatment to determine the time to initiate the treatment comprising the metal salt and the promoter, and / or the concentration of the metal salt and the promoter in the treatment composition.

[0050] If desired, additional corrosion prevention and / or water treatment chemistries known in the art can be introduced into the system in combination with the combined feed to further improve corrosion performance and control the deposition of undesirable species. As will be appreciated, the treatment methods according to the present disclosure can be combined with other treatment or conditioning chemistries that would be impaired by the continuous presence of corrosion inhibitors. Alternatively, a "more environmentally friendly" treatment package or a treatment package designed to address other parameters of system operation can be utilized during intermittent feeds to improve the quality of the system effluent and / or reduce the need for effluent treatment prior to discharge.

[0051] According to one embodiment, the treatment composition may include a reducing agent. Controlling the amount of the reducing agent, including frequency, duration, and concentration, according to the methods described herein can result in a more effective corrosion inhibition method. The reducing agent may be, for example, erythrobate, a hydroxyphosphonocarboxylic acid-based complexing agent, or a combination thereof.

[0052] The treatment composition can include adding a metal salt together with one or more secondary corrosion inhibitors including, for example, inorganic and organic phosphates, zinc salts, nitrites / nitrates, molybdates, chromates, polyacrylic acid, unsaturated carboxylic acid polymers such as homo- or copolymaleic acid (synthesized from solvent and aqueous routes); acrylate / 2-acrylamido-2-methylpropanesulfonic acid (AMPS) copolymer, acrylate / acrylamide copolymer, acrylate homopolymer, terpolymer of carboxylate / sulfonate / maleate, terpolymer of acrylic acid / AMPS; phosphonates and phosphinates such as 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotris(methylenephosphonic acid) (ATMP), 2-hydroxyphosphonocarboxylic acid (HPA), diethylenetriaminepenta(methylenephosphonic acid) (DETPMP), phosphinobutane succinic acid oligomer (PSO); salts of molybdenum and tungsten including, for example, nitrates and nitrites; amines such as N,N-diethylhydroxylamine (DEHA), diethylaminoethanol (DEAE), dimethylethanolamine (DMAE), cyclohexylamine, morpholine, monoethanolamine (MEA), azoles such as tolyltriazole (TTA), benzotriazole (BZT), butylbenzotriazole (BBT), halogenated azoles and salts thereof.

[0053] The treatment composition may further comprise at least one chelating agent such as azole-based copper corrosion inhibitors such as citric acid, benzotriazole and (Z)-2-butenedioic acid, and halogenated azoles and their derivatives. The treatment composition may be polyacrylic acid, homo- or copolymaleic acid (synthesized from solvents and aqueous routes), acrylate / 2-acrylamido-2-methylpropanesulfonic acid (APMS) copolymer, acrylate / acrylamide copolymer, acrylate homopolymer, carboxylate / sulfonate / maleate terpolymer, acrylic acid / AMPS terpolymer, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotris(methylenephosphonic acid) (ATMP), 2-hydroxyphosphonocarboxylic acid (HPA), diethylenetriaminepenta(methylenephosphonic acid) (DETPMP), phosphinobutane succinic acid oligomer (PSO) and other unsaturated carboxylic acid polymers; salts of molybdenum and tungsten containing nitrates and nitrites; N,N-diethylhydroxylamine (DEHA), diethylaminoethanol (DEAE), dimethylethanolamine (DMAE), cyclohexylamine, morpholine, monoethanolamine (MEA) and other amines, biocides, and scale inhibitors and dispersants selected from the group consisting of one or more of these combinations may be further included.

[0054] In another embodiment, a chemical treatment composition is provided for inhibiting corrosion of a corrosive metal surface in contact with an aqueous water stream. The composition comprises a combination of a salt of a polyvalent metal and a hydroxycarboxylic acid promoter as described herein. The composition may be an aqueous composition supplied to the aqueous water stream.

[0055] In an embodiment, the treatment composition can be introduced into an open or closed aqueous system. Further, the treatment can be applied to the water stream while the aqueous system is online. Alternatively, the treatment composition may be introduced into the water stream while the system is offline, such as during pretreatment of the corrosive metal surface before the device is used in the aqueous system.

Examples

[0056] The following examples illustrate the application of the processing methods disclosed in this specification. In the examples, the chemical concentrations used are expressed in parts per million (ppm). The unit of the corrosion rate is mils per year (mpy). The corrosion inhibition efficiency was calculated according to the following formula.

Number

[0057] The chemical properties of the water used in these examples are as follows.

[0058]

Table 1

[0059]

Table 2

[0060] In each example, a carbon steel 1010 coupon was used, and the corrosion rate was measured using a 10 L "spinner bath" apparatus. The corrosion rate was calculated over 3 days at 50°C.

[0061] Example I In this example, Examples 1-2 and Comparative Example 1 were tested in the above alkaline water chemistry. The examples have the indicated amounts of gluconic acid, tin (from stannous chloride), and aluminum. In each example, 100 ppm of the additive was introduced. The results are shown in Table 1 below.

[0062]

Table 3

[0063] Examples 3 to 4 and Comparative Example 2 were tested in the above neutral water chemistry. The examples have glucaric acid, tin (from stannous chloride), and aluminum in the amounts indicated. In each example, 100 ppm of the additive was introduced. The results are shown in Table 2 below.

[0064]

Table 4

[0065] As can be seen in Tables 1 and 2, Examples 1 to 4 corresponding to the disclosed embodiments resulted in substantially better corrosion rates than Comparative Examples 1 to 2. By adding aluminum to the tin / glucaric acid combination, an improvement of about 20% was observed. Similar improvements were observed in both alkaline and neutral pH water conditions.

[0066] This data indicates that substantially less tin inhibitor can be used when aluminum is included, which is very beneficial since tin is by far the most expensive component. Furthermore, the best results were obtained when using less tin by combining aluminum within the acceptable ranges of the disclosed embodiments. These results suggest that the treatment method using a combination of tin, aluminum, and glucaric acid provides a better corrosion rate with lower concentrations of inhibitor, metal salt, and accelerator compared to conventional methods using tin and glucaric acid alone.

[0067] In summary, the treatment method using a combination of tin, aluminum, and glucaric acid provides a dramatically better corrosion rate while allowing for substantially less tin usage than required in conventional methods using tin and glucaric acid alone to achieve comparable corrosion resistance.

[0068] Example II In this example, various samples were tested in alkaline water chemistry at ambient temperature as shown in the following table.

[0069]

Table 5

[0070] As can be seen from the plot of Figure 1, Example 6 showed the best corrosion resistance, as evidenced by the large diameter of its Nyquist plot.

[0071] Example III In this example, as shown in the following table, various samples were tested in alkaline water chemistry at ambient temperature.

[0072]

Table 6

[0073] As can be seen from Figures 2A and 2B, Example 6 showed the best corrosion resistance, as evidenced by the leftmost branch (resistance to corrosion) of the EIS plot along the x-axis.

[0074] It will be understood that the features and functions disclosed above, or alternatives thereof, may desirably be combined in different systems or methods. Also, various alternatives, modifications, variations, or improvements may be made later by those skilled in the art and are intended to be encompassed by the following claims. Accordingly, various changes may be made without departing from the spirit and scope of the disclosure as defined by the claims.

Claims

1. A method for suppressing corrosion of a corrosive metal surface in contact with a water flow in an aqueous system, comprising introducing a treatment composition containing a combination of a passivating agent and a hydroxycarboxylic acid accelerator into the water flow, wherein the hydroxycarboxylic acid accelerator has a carboxylic acid group and a hydroxyl group bonded to a carbon atom adjacent to the carboxylic acid group, and the treatment composition is introduced such that the concentration of the combination of the passivating agent is in the range of 0.1 to 10 ppm and the concentration of the accelerator in the water flow is in the range of 2 ppm to 50 ppm, method.

2. The method for suppressing corrosion according to claim 1, wherein the treatment composition is introduced such that the concentration of the combination of the passivating agent is in the range of 0.25 to 1.25 ppm and the concentration of the accelerator in the water flow is in the range of 7.5 ppm to 20 ppm.

3. The method for suppressing corrosion according to claim 1, wherein the passivating agent comprises a combination of salts of polyvalent metals selected from at least two kinds selected from the group consisting of manganese, tungstate, aluminum, and tin.

4. The method for suppressing corrosion according to claim 1, wherein the passivating agent contains tin.

5. The method for suppressing corrosion according to claim 3, wherein the tin is provided as a stannous salt selected from the group consisting of stannous sulfate, stannous bromide, stannous chloride, stannous oxide, stannous phosphate, stannous pyrophosphate, and stannous tetrafluoroborate.

6. The method for suppressing corrosion according to claim 1, wherein the passivating agent contains tin and aluminum.

7. The method for suppressing corrosion according to claim 6, wherein the aluminum is supplied as an inorganic aluminum salt selected from the group consisting of aluminum chloride, aluminum citrate, aluminum gluconate, aluminum nitrate, and aluminum sulfate.

8. The method for suppressing corrosion according to claim 6, wherein the aluminum is supplied as an organic aluminum salt selected from the group consisting of aluminum citrate and aluminum gluconate.

9. The method for suppressing corrosion according to claim 1, wherein the hydroxycarboxylic acid-based accelerator is selected from the group consisting of tartaric acid, glucaric acid, glucoheptonic acid, and gluconic acid.

10. The method for suppressing corrosion according to claim 9, wherein the hydroxycarboxylic acid-based accelerator is glucaric acid.

11. The method for suppressing corrosion according to claim 1, wherein the treatment composition further comprises at least one reducing agent selected from the group consisting of erythrobate, glycolic acid or other aliphatic polycarboxylic acids, aminocarboxylic acids, phosphonocarboxylic acids, hydroxycarboxylic acids, and hydroxyphosphonocarboxylic acid-based complexing agents.

12. The method for suppressing corrosion according to claim 1, wherein the treatment composition further comprises at least one dispersant polymer selected from the group consisting of unsaturated carboxylic acid polymers, phosphonates and phosphinates, amines, and biocides.

13. The method for suppressing corrosion according to claim 1, wherein the aqueous system is selected from the group consisting of cooling towers, distribution systems, boilers, pipelines carrying water / brine, and storage tanks.

14. The method for suppressing corrosion according to claim 1, wherein the corrosive metal surface is a metal or alloy selected from the group consisting of ferrous metals, aluminum metals, brass, copper-containing alloys, mild steel, carbon steel, and zinc-plated steel.

15. The method for suppressing corrosion according to claim 1, wherein the treatment composition is provided in an amount and for a time sufficient to form a stable protective film on at least a portion of the corrosive metal surface.

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