JP2010535324A - Methods and compositions for passivating heat exchanger systems - Google Patents

Abstract

  A method of processing heat exchanger system parts is provided. In this method, by contacting the metal surface with a phosphate-containing solution, the phosphate-containing solution passes through the coolant in the heat exchanger system so that the metal surface is passivated for subsequent contact with the coolant. Heat exchanger parts having metal surfaces that interact chemically and detrimentally with other additives are processed.

Description

  The present invention relates generally to compositions and methods for passivating the surfaces of components and parts in heat exchanger systems that use a coolant for heat transfer.

The method of manufacturing heat exchange systems has changed over the years with the increasing use of lighter materials such as aluminum and its alloys. Construction methods have also changed with the use of CAB with brazing, eg, controlled atmosphere brazing or brazing in a controlled N ₂ gas environment using a potassium fluoroaluminate flux. A flux is applied to the surfaces of the heat exchange parts to be joined, and the assembled unit is heated in an N ₂ environment and joining occurs.

  A coolant (heat transfer fluid) is used to remove heat from a heat exchange system such as an engine. It is known to add corrosion inhibitors to coolants to reduce metal-based corrosion. For example, US Pat. No. 4,664,833 discloses a coolant system that uses a corrosion inhibiting amount of nitrate. U.S. Pat. No. 4,587,028 discloses a non-silicate antifreeze formulation comprising an alkali metal salt of benzoic acid, dicarboxylic acid and nitric acid. US Pat. No. 4,647,392 discloses a corrosion inhibitor comprising a combination of an aliphatic monoacid or salt, a hydrocarbyl dibasic acid or salt and a hydrocarbonyltriazole.

  Brazed materials have been used in cooling systems for decades. Previously (see ASTM STP705 (April 1979), "Corrosion Testing of Furnace and Vacuum Brazed-Aluminum Radiators"), the materials used to braze aluminum are chemically resistant to cooling system liquids. It has been considered inert. Recent studies have shown that the presence of flux in heat exchanger systems such as radiators generally increases the corrosion rate of the coolant used in the system. By Jeffcoate et al., "Investigation of Interaction Between Coolant Formulations and Flux Loading / Compositions in Controlled Atmosphere Brazed (CAB) Aluminium Surfaces in Heat Exchanger Applications", Journal of ASTM International, Vol. 4 (No. 1), referring to the report ID JAI100421 I want to be. In another test, some coolant inhibitors in heat exchangers, especially nitrogen and silicate-based inhibitors, disappear very quickly as the pH of the coolant used in the system increases. Which has been shown to have a severe impact on the performance of the coolant.

  Includes a controlled amount of zinc and phosphate ions, sufficient time to form a uniform and dense phosphorylated coating that is adhesive and anti-corrosive and is particularly useful as a base coat for electrodeposition coatings It is known in the art to treat metal surfaces by soaking in an aqueous acidic phosphoric acid solution. However, although it is known that phosphate prevents corrosion of aluminum, it is not acceptable to many original equipment manufacturers. For example, Ford Engineering Material Specifics, “Coolant, Organic Additive Technology, Concentrate”, Specification No. See WSS-M97BB44-C.

  There is a need to extend the life of the coolant in heat exchanger systems that use aluminum and alloy parts, particularly systems that have brazed parts. In one embodiment, the present invention utilizes a solution containing phosphate ions to clean / passivate the aluminum parts and components of the heat exchanger system prior to contact with the coolant, and the heat exchanger system The present invention relates to a novel method for extending the life of a coolant in

  In some embodiments, the parts in the heat exchanger system are treated so that the phosphate-containing solution passivates the metal surface against subsequent contact with the coolant by contacting the metal surface with the phosphate-containing solution. Although the method is provided, the part has a metal surface that interacts chemically and detrimentally with additives in the coolant in the heat exchanger system.

  In another aspect, the invention provides a phosphate for treating parts in a heat exchanger system, having a pH of 4.0-12.0 and comprising 0.005-30 g / l phosphate ions. With regard to the use of the containing solution, the part has a metal surface that interacts chemically and detrimentally with additives in the coolant in the heat exchanger system. In the treatment method, phosphate ions in the phosphate-containing solution reduce the chemical activity of the metal surface for subsequent contact with the coolant.

  In order to facilitate a further understanding of the invention, the following term definitions are provided herein.

  As used herein, the term “heat exchange system” means an application in which a cooling system is used, including, but not limited to, application to fuel cell assemblies, appliances and engines. . Non-limiting examples include heating for engines commonly used in automobiles, trucks, motorcycles, airplanes, trains, tractors, generators, compressors, various stationary engines and equipment, marine engines, etc. Including a ceramic core and a radiator.

  As used herein, the term “heat exchange component” includes but is not limited to radiators, water pumps, thermostats, engine heads, cylinder liners, fuel cell separators, heater cores, etc. Means a heat exchange part, main body, or component.

  As used herein, the terms “treating”, “treating”, and “treated” refer to “passivate”, “passivate”, “passivate”. In order to reduce the chemical activity of the cleaned surface that would subsequently come into contact with the coolant in the heat exchanger system. Reference is made to an embodiment of the invention which is washed (contacted) with a phosphate-containing solution.

  The term “heat transfer liquid” refers to a liquid that flows through a heat exchange system to transfer heat generated in the system to another system or device that can utilize or dissipate the heat and prevent its overheating.

  As used herein, the term “antifreeze” composition (or liquid or concentrate) is the term “coolant”, “heat transfer liquid” or “deicing liquid” (composition or concentrate). And can be used interchangeably.

  As used herein, the term “glycol-based” also includes glycols, glycerin, and glycol ethers.

  In one embodiment of the invention, a method is provided for treating surfaces of heat exchanger parts, such as heater cores, radiators and brazed parts. The part is treated with a passivating solution to reduce the chemical reactivity of its surface.

  Passivation solution: The composition for passivating the surface in the heat exchange system has a pH range of 4.0 to 12.0 and contains phosphate ions as its essential component. In the second embodiment, the composition is a neutral to slightly alkaline solution having a pH of 6.5 to 11 and containing phosphate ions.

  Phosphate ions are present in the solution in an amount sufficient to reduce the chemical activity of the surface in contact with the coolant. In certain embodiments, a sufficient amount of phosphate ions is 0.005 to 30 g / l in solution. In a second embodiment, phosphate ions are present in the solution in an amount of 0.01 to 25 g / l. In 3rd Embodiment, it is 1-15 g / l. In 4th Embodiment, it is 0.5-12 g / l. In 5th Embodiment, it is 0.3-10 g / l.

Phosphate ions can be introduced into the solution in the form of any soluble phosphate compound, including alkali metal phosphates, ammonium phosphates, polyphosphates, pyrophosphates, phosphates, and the like. In certain embodiments, the passivating solution comprises dipotassium hydrogen phosphate (K ₂ HPO ₄ ) in the solution. In the second embodiment, the solution contains monopotassium phosphate (KH ₂ PO ₄ ) in an aqueous solution. In a third embodiment, the passivating solution is a diammonium phosphate solution.

  In some embodiments, the passivating solution is water-based with an aqueous medium selected from the group consisting of water, neutral aqueous solution, acidic aqueous solution and basic aqueous solution. In a second embodiment, the passivating solution is water with a sufficient amount of at least one alkali metal hydroxide, such as NaOH or KOH, added so that its pH is between 7-10. Contains dipotassium hydrogen phosphate in the base. In a third embodiment, the passivating solution has as its base a glycol-based or non-glycol-based coolant, so that a glycol or non-glycol-based antifreeze is used in the system as a heat transfer liquid. The Rukoto.

  In certain embodiments, the phosphate-containing passivating solution has as its base a glycol-based solution comprising glycol or glycol ether in an amount of 2 to 97% by weight of the total weight of the final passivating solution. In a second embodiment, the amount of glycol or glycol ether ranges from 2 to 50% by weight. Non-limiting examples include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol; triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene Alkylene glycols such as glycol, hexapropylene glycol, and mixtures thereof, and glycol monoethers such as methyl, ethyl, propyl, and butyl ethers of ethylene glycol and mixtures thereof.

  In yet another embodiment, the phosphate-containing passivating solution contains at least one alkali metal salt of an anion selected from acetate, formate, propionate, adipate, and succinate, It has as its base a non-glycolic aqueous medium containing in an amount of 2-97% by weight of the total weight of the passivating solution. Suitable examples of non-glycol based aqueous media include, but are not limited to, glycerin, ethanol, potassium formate, potassium propionate, potassium acetate, dipotassium adipate and mixtures thereof.

  In certain embodiments, one or more ingredients known in the art as “phosphorylation promoters” are optionally added to passivate in order to allow the surface to be more uniformly treated with phosphate ions. It can also be added to the crystallization solution. Examples include m-nitrobenzenesulfonate ion at 0.05-2 g / L, hydroxylamine in free or bound form at 0.1-10 g / l, m-nitrobenzoate ion at 0.05-2 g / l. P-nitrophenol at 0.05-2 g / l, hydrogen peroxide in free or bound form at 1-70 mg / l, organic N-oxide at 0.05-10 g / l, 0.1-3 g / l Nitroguanidine, 1 to 500 mg / l nitrite ions, and 0.5 to 5 g / l chlorate ions.

  In yet another embodiment, conventional corrosion inhibitors known in the art can optionally be added to the phosphate-containing solution in an amount ranging from 0.005 to 10% by weight. Non-limiting examples include triazoles, nitrates, nitrites, silicates, borates, molybdates, salts of organic aromatic or aliphatic acids, and mixtures thereof. In some embodiments, the phosphate-containing passivating solution comprises an alkali metal borate, an alkali metal silicate, an alkali metal benzoate, an alkali metal nitrate, an alkali metal nitrite, an alkali metal molybdate, hydrocarbyl It further comprises at least one corrosion inhibitor selected from the group of bilthiazole and mixtures thereof.

  The combination of soluble phosphate compound and optional additives can be mixed into the aqueous medium matrix alone or in various subcombinations to formulate a passivating solution. The passivating solution may be in the form of a single package, or one containing the passivating solution (with phosphate ions) and a coolant dilution form for later use in the heat exchanger system. It may be in the form of two packages with one containing.

  Method for treating / passivating a surface in a heat exchanger system: In one embodiment, the treating / passivating process comprises maintaining the passivating solution in a temperature range of 20-90 ° C. It is carried out in a temperature range of 140 ° C. In certain embodiments, the treatment process is performed at room temperature.

  Passivation solutions can be applied to the surface to be treated using methods known in the art, including spraying, dipping, circulating liquids in a cooling system, or by a non-rinsing method such as using a roller. Applicable. Regardless of whether the passivating solution is applied by spraying, a non-rinsing method, or dipping, in certain embodiments, the treatment time is between 5 seconds and 12 hours. In the second embodiment, the time is 30 seconds to 6 hours. In the third embodiment, the processing time is between 5 minutes and 2 hours. In the fourth embodiment, the processing time ranges from 15 to 60 minutes.

  In certain embodiments, after treatment with the passivating solution, the heat exchanger system may remove moisture, and the treated part is optionally rinsed with a rinsing solvent, such as deionized water. In another embodiment, the system may be rinsed with a dilute concentration of cooling liquid added to the heat exchanger system, thereby reducing the amount of any passivating solution that may remain in the system and / or any residual effects. Can be minimized. Finally, after processing (and optionally a rinsing step), a coolant for normal operation of the heat exchanger system can finally be added to the system.

  In some embodiments, the treatment with the passivating solution may clean the surfaces of the parts / components in the heat exchange system. The solution may also remove oil, sludge, corrosion products and other unwanted contaminants and / or deposits on the surface of the part. The composition may disperse and / or dissolve such chemical species in a solution, which is subsequently removed / drained with undesirable chemical species in an optional rinsing step.

  Application: Passivation solutions are useful for the treatment of heat exchanger systems with metal parts containing components that interact chemically and detrimentally with additives in the coolant. As used herein, the term “chemically and detrimentally interacting with additives” means that at least one additive in the coolant is corrosive, as measured by the amount of active ingredient in the additive. In at least one additive, such as an inhibitor, means a decrease in its potency and / or useful life by at least a 25% decrease after 2 weeks of use. Adverse chemical interactions can also be shown in changes in the pH of the coolant over time, eg, at least ± 1 pH change after 2 weeks.

  In certain embodiments, the method is for processing heat exchanger parts formed by processes including casting, rolling, forming, brazing, and combinations thereof. In another embodiment, the method is for processing heat exchanger parts comprising zinc, magnesium, aluminum, alloys of those materials. In yet another embodiment, the method is for processing heat exchanger parts comprising aluminum and / or alloys thereof.

  In one embodiment, the method is for treating a heat exchanger part brazed with a flux material that interacts chemically and detrimentally with additives in the coolant. In another embodiment, the method is for treating parts brazed with a fluorine-containing flux. Non-limiting examples of fluorine-containing flux materials include potassium borofluoride, potassium fluorinated aluminate, cesium fluorinated aluminate, potassium fluorinated zincate, cesium fluorinated zincate, and mixtures thereof.

  In certain embodiments, the treatment with the passivating solution substantially deactivates the chemical reactivity of the metal surface in the heat exchanger system to the coolant. In some embodiments of organic acid technology (OAT) coolants using conventional inhibitors such as nitrite, use for 2 weeks when coolant is added to the heat exchanger system using the treated parts The treatment stabilizes the disappearance of nitrite so that the subsequent decrease in nitrite level is less than 25%. In a second embodiment, the nitrite reduction level is less than 10%. In a third embodiment, the stabilizing effect of the passivation treatment is demonstrated at the coolant pH level, where the coolant pH remains essentially constant, i.e. less than 10% after 2 weeks of use. Showing change.

  The following examples are given as non-limiting illustrations of aspects of the present invention.

In the examples, two types of coolant formulations are used, OAT coolants and conventional mineral-based coolants, both from Chevron Corporation. The coolant has a composition using the components shown in Table 1.

  In the examples, cut specimens (cubes) 1/2 "to 1" in size of brazed aluminum radiator parts were treated by immersion in a cleaning solution for 15 minutes to overnight (10 hours). The parts were brazed with potassium fluoroaluminate, conventionally considered to be an inert material under normal conditions as a flux material. After cleaning, the cut specimens were immersed in OAT coolant for 2 weeks with the coolant bath temperature maintained at about 195 ° F. (90.56 ° C.). In all examples, the OAT coolant has an initial pH of 8.5 and a nitrite level of 580 ppm. The pH level, nitrite and fluoride content of the OAT coolant are measured after 2 weeks of testing.

The cleaning liquid formulation E is an aqueous solution using 1 to 2% by weight of dipotassium hydrogen phosphate (K ₂ HPO ₄ ). The corrosion inhibitor components constituting the cleaning liquid formulations C to G are shown in Table 2 below, and the phosphate ions in the cleaning liquid formulations E to G are due to dipotassium hydrogen phosphate (K ₂ HPO ₄ ) in the cleaning aqueous solution. Supplied.

In Example 1, the cut specimen was not treated / washed at all. In Example 2, the cut specimen was washed with water. In Examples 3-7, the cut specimens were treated with a cleaning solution having the composition shown in Table 2. Cleaning composition E~G-water 0.4 to 2 wt% of _K 2 _HPO 4, OAT coolant, or had a conventional mineral coolant.

Passivation treatment has been found to be equally effective with short treatment times (eg 15 minutes) or longer treatment times (overnight). The results of the examples in Table 3 show that once treated with E and F, neither abnormal disappearance nor pH change is observed when contacted with a standard coolant. Furthermore, there is no intense release of fluoride, which is an indicator of the reactivity of potassium fluoroaluminate with coolants commonly used in heat exchanger systems.

  For purposes of this specification and the appended claims, unless expressly stated otherwise, all numbers, percentages, or ratios, and all other numbers, are in all cases the term “about”. Should be understood to be modified by Thus, unless expressed differently, the numerical parameters described so far are approximations that can vary according to the desired characteristics sought to be obtained by the present invention. It should be noted that as described herein, singular notation encompasses a plurality of indicating objects, unless explicitly and explicitly limited to a single indicating object. As used herein, the term “comprising” and its grammatical variations are intended to be non-limiting. Thus, listing items in the form of a list is not to exclude other similar items that may be replaced or added to the listed items.

  The written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other embodiments may have structural elements that do not differ from the language of the claims, or equivalent structural elements that have non-essential differences from the language of the claims. If included, it is intended to be within the scope of the claims. All citations referred to herein are expressly incorporated herein by reference.

Claims (12)

  A method of treating a part in a heat exchanger system having at least partially a metal surface that chemically and deleteriously interacts with an additive in a coolant in the heat exchanger system, the metal surface being phosphated A method comprising the step of contacting with a containing solution, wherein the phosphate containing solution passivates the metal surface for subsequent contact with a cooling liquid.   The method of claim 1, wherein the heat exchange system comprises a component comprising aluminum and / or an alloy thereof, and a metal surface to be passivated by the phosphate-containing solution is brazed.   The method of claim 2, wherein the metal surface is brazed with a fluorine-containing flux.   The fluorine-containing flux material is selected from the group of potassium borofluoride, potassium fluorinated aluminate, potassium fluorinated aluminate, cesium fluorinated aluminate, potassium fluorinated zincate, cesium fluorinated zincate, and mixtures thereof 4. The method of claim 3, wherein:   The method of claim 1 for treating a heat exchanger system selected from the group of radiators, water pumps, thermostats, engine heads, cylinder liners, fuel cell separators, and heater cores.   The method of claim 1 for treating a heat exchanger system having a part formed by at least one of casting, brazing, molding, rolling, and combinations thereof.   The method of claim 1, wherein the phosphate-containing solution comprises 0.005 to 30 g / l phosphate ions and has a pH of 4.0 to 12.0.   The method of claim 7, wherein the composition has a pH of 6.5-11.   The phosphate ion in the phosphate-containing solution is derived from at least one of an alkali metal phosphate, ammonium phosphate, polyphosphate, pyrophosphate, phosphoric acid, and mixtures thereof. The method described in 1. The phosphate-containing solution comprises _K 2 HP0 ₄ 1-2 wt% in the solution, The method of claim 7.   4.0 to 12.0 for treating parts in a heat exchanger system having at least partially a metal surface that interacts chemically and detrimentally with additives in the coolant in the heat exchanger system A phosphate-containing solution having a pH of 0.005 to 30 g / l of phosphate ions, wherein the phosphate ions in the phosphate-containing solution are metal for subsequent contact with the coolant. Use to reduce the chemical activity of the surface.   The phosphate ion in the phosphate-containing solution is derived from at least one of an alkali metal phosphate, ammonium phosphate, polyphosphate, pyrophosphate, phosphoric acid, and mixtures thereof. Use as described in.