Method for producing a heat exchanger

Abstract

A method for producing a heat exchanger having at least one cooling line with a lightweight metal base through which a water-based coolant can flow may include passivating a surface of the at least one cooling line, which is in contact with the coolant, before the at least one cooling line is filled with the coolant.

Claims

1. A method for producing a heat exchanger having at least one cooling line with a metal base, through which a water-based coolant can flow, comprising: pretreating a surface of the at least one cooling line with a first pretreatment, the first pretreatment including a pickling treatment with an alkaline solution; and pretreating the surface with a second pretreatment after the first pretreatment, the second pretreatment including a pickling treatment with an acid mixture including sulphuric acid and phosphoric acid; passivating the surface, which is in contact with the coolant, before the at least one cooling line is filled with the coolant; wherein passivating the surface is carried out by a chemical treatment with a passivation solution constituted on the basis of one of an aqueous sulphuric acid solution or an organic acid solution, and wherein the passivation solution contains 0.1-1 wt % sebacic acid, 20-50 wt % zirconium carbonate, and 0.05-0.5 wt % triethanolamine; and wherein the alkaline solution has a pH value from 8-9.

2. The method according to claim 1, wherein passivating the surface is carried out in such a manner that an electrical input conductivity of the coolant increases by less than 100 μS/cm during operation.

3. The method according to claim 1, wherein the passivation solution further includes at least one corrosion inhibitor, which makes up 0.005-10 wt % of the passivation solution.

4. The method according to claim 3, wherein the at least one corrosion inhibitor is selected from the following group of chemical compounds: pyrocatechol-3,5-disulphonic acid disodium salt, diethylenetriamine-penta-acetic acid, 8-hydroxy-(7)-iodo-quinoline-sulphonic acid-(5), 8-hydroxy-quinoline-5-sulphonic acid, mannitol, 5-sulphosalicylic acid, aceto-O-hydroxamide acid, norepinephrine, 2-(3,4-dihydroxyphenyl)-ethylamine, L-3,4-dihydroxyphenyl alanine (L-DOPA), 3-hydroxy-2-methyl-pyran-4-oη), citrates, carboxylates, alkaline salts of stearate and/or formiate and/or glyconate, and inorganic inhibitors such as sodium tetraborate, pyrophosphoric acid, calcium gluconate.

5. The method according to claim 1, further comprising prewarming the at least one cooling line before passivating the surface.

6. The method according to claim 1, further comprising prewarming the passivation solution, and then introducing the passivation solution into the at least one cooling line.

7. The method according to claim 5, wherein a temperature of the passivation solution is below a temperature of the at least one cooling line.

8. The method according to claim 1, wherein a reaction time during which passivating the surface takes place lasts for 0.5-3 hours.

9. The method according to claim 1, wherein the alkaline solution is heated to a temperature of 40-60° C.

10. The method according to claim 1, wherein the acid mixture contains at least 1-5 wt % of the sulphuric acid and phosphoric acid, and is 95-99 wt % demineralized water.

11. The method according to claim 1, carrying out multiple rinsing cycles of the surface of the at least one cooling line with demineralised water after at least one of the first pretreatment, the second pretreatment, and passivating the surface.

12. The method according to claim 1, wherein the passivation solution is constituted on the basis of the aqueous sulphuric acid solution and has a pH value of 2-6.

13. The method according to claim 5, wherein the at least one cooling line is prewarmed to 90° C.-120° C.

14. A method for producing a heat exchanger having at least one cooling line with a metal base, through which a water-based coolant can flow, comprising: passivating a surface of the at least one cooling line, which is in contact with the coolant, before the at least one cooling line is filled with the coolant; prewarming the at least one cooling line before passivating the surface; and wherein passivating the surface is carried out by a chemical treatment with a passivation solution constituted on the basis of one of an aqueous sulphuric acid solution or an organic acid solution, and wherein the passivation solution contains 0.1-1 wt % sebacic acid, 20-50 wt % zirconium carbonate, and 0.05-0.5 wt % triethanolamine.

15. A method for producing a heat exchanger having at least one cooling line with a metal base, through which a water-based coolant can flow, comprising: passivating a surface of the at least one cooling line, which is in contact with the coolant, before the at least one cooling line is filled with the coolant; wherein passivating the surface is carried out by a chemical treatment with a passivation solution constituted on the basis of one of an aqueous sulphuric acid solution or an organic acid solution, and the passivation solution includes at least one corrosion inhibitor, which makes up 0.005-10 wt % of the passivation solution; and wherein the passivation solution contains 0.1-1 wt % sebacic acid, 20-50 wt % zirconium carbonate, and 0.05-0.5 wt % triethanolamine.

16. The method according to claim 15, wherein the passivation solution is constituted on the basis of the aqueous sulphuric acid solution and has a pH value of 2-6.

17. The method according to claim 15, wherein the at least one corrosion inhibitor is selected from the following group of chemical compounds: pyrocatechol-3,5-disulphonic acid disodium salt, diethylenetriamine-penta-acetic acid, 8-hydroxy-(7)-iodo-quinoline-sulphonic acid-(5), 8-hydroxy-quinoline-5-sulphonic acid, mannitol, 5-sulphosalicylic acid, aceto-O-hydroxamide acid, norepinephrine, 2-(3,4-dihydroxyphenyl)-ethylamine, L-3,4-dihydroxyphenyl alanine (L-DOPA), 3-hydroxy-2-methyl-pyran-4-oη), citrates, carboxylates, alkaline salts of stearate and/or formiate and/or glyconate, and inorganic inhibitors such as sodium tetraborate, pyrophosphoric acid, calcium gluconate.

18. The method according to claim 14, wherein the passivation solution is constituted on the basis of the aqueous sulphuric acid solution and has a pH value of 2-6.

19. The method according to claim 14, wherein the at least one cooling line is prewarmed to 90° C.-120° C.; and further comprising prewarming the passivation solution to a temperature of 40° C.-80° C. and at least 40° C. below that of the at least one coolant line.

Description

DETAILED DESCRIPTION

(1) The following text is an exemplary process description of the method according to the invention for producing a heat exchanger of such kind, wherein the individual method steps are protected both individually and also in any combination within the scope of the invention.

(2) For the passivation of the heat exchanger, a pickling pretreatment of the aluminium surface is advantageous. In this context, the heat exchanger may be flushed with a mildly alkaline solution having a pH vale of 7.5-12, preferably a pH value of 8-9, at 40-60° C. Then, the heat exchanger may be flushed with demineralised water, preferably several times. This may then be followed by a second pickling treatment with an acid that has been diluted with demineralised water. For example, a mixture of sulphuric acid and phosphoric acid may be used as the pickling acid solution. The acid is present in the demineralised water preferably in a concentration of 1-5 wt %, particularly preferably 2-3 wt %. In addition, the dilute acid may further contain 50-1000 ppm free fluorides. To complete the pickling pretreatment of the aluminium surface, preferably at least several flushing cycles may be performed with demineralised water. The pickling pretreatment is then followed by the actual passivation of the aluminium surface. For this purpose, the part is preferably warmed to 90-120° C. and then filled with a prewarmed passivation fluid, which will be explained in greater detail below. After a reaction time of 0.5-3 hours, the passivation is complete. After this, the part is flushed out preferably at least several times. The passivation fluid is preferably constituted from an aqueous sulphuric acid solution with pH value 2-6, wherein the following substances are dissolved preferably at a temperature of 40-80° C. The substances which are preferably dissolved in the passivation fluid are in particular sebacic acid 0.1-1 wt %, zirconium carbonate 20-50 wt % and triethanolamine 0.05-0.5 wt %. Corrosion inhibitors may also be added to the passivation fluid. The preferred quantity of the corrosion inhibitors used as additives according to the invention is preferably 0.005-10 wt %, particularly preferably 0.01-2 wt %.

(3) In an advantageous variant of the idea according to the invention, the passivation is carried out in such manner that the electrical conductivity between the coolant and the cooling line of the heat exchanger is lower than 100 μS/cm and preferably lower than 50 μS/cm.

(4) Another advantageous variant provides that the passivation of the surface is carried out in a chemical treatment with a passivation solution prepared on the basis of an aqueous sulphuric acid solution or organic acid solution, preferably with pH value 2-6.

(5) In an advantageous embodiment, the passivation solution contains at least 0.1-1 wt % sebacic acid and/or at least 20-50 wt % zirconium carbonate and/or 0.05-0.5 wt % triethanolamine.

(6) In an advantageous further development, the passivation solution further contains at least one corrosion inhibitor, which makes up a fraction of 0.005-10 wt %, preferably 0.01-2 wt % of the passivation solution.

(7) An advantageous variant provides that the at least one corrosion inhibitor is selected from the following group of chemical compounds: pyrocatechol-3,5-disulphonic acid disodium salt, diethylenetriamine-penta-acetic acid, 8-hydroxy-(7)-iodo-quinoline-sulphonic acid-(5), 8-hydroxy-quinoline-5-sulphonic acid, mannitol, 5-sulphosalicylic acid, aceto-O-hydroxamide acid, norepinephrine, 2-(3,4-dihydroxyphenyl)-ethylamine, L-3,4-dihydroxyphenyl alanine (L-DOPA), 3-hydroxy-2-methyl-pyran-4-oη), citrates, carboxylates, in particular oxalates, alkaline salts of stearate and/or formiate and/or glyconate, and inorganic inhibitors such as sodium tetraborate, pyrophosphoric acid, calcium gluconate.

(8) In an advantageous further development of the method according to the invention, the heat exchanger, in particular cooling line that is to be passivated is prewarmed, preferably to 90-120° C., prior to the passivation.

(9) A further advantageous embodiment provides that the passivation solution is prewarmed, preferably to 40-80° C., before it is introduced into the cooling line that is to be passivated.

(10) In a further advantageous variant, the temperature of the passivation solution is below, preferably at least 40° C. below the temperature of the cooling line that is to be passivated.

(11) A further expedient embodiment provides that a reaction time during which the passivation of the cooling line surface takes place lasts for 0.5-3 hours. It should be noted that the reaction time may be of any duration without departing from the scope of the invention. No substantial further improvement of the passivation layer is achievable with a reaction time longer than 3 hours.

(12) In an advantageous further development of the method, the cooling line surface that is to be passivated is pretreated for a first time preferably before the passivation by pickling with a mildly alkaline solution which preferably has a pH value of 7.5-12. The pickling pretreatment of the surface to be passivated may be repeated any number of times.

(13) A further advantageous variant provides that the mildly alkaline solution has a pH value of 8-9 for the first pretreatment of the surface to be passivated, and is heated to a temperature of 40-60° C.

(14) In an advantageous variant, the surface to be passivated undergoes a second pretreatment after the first pretreatment, which second pretreatment consists of a picking treatment with an acid mixture of sulphuric acid and/or phosphoric acid. It is also conceivable that the acid mixture contain an amidosulphonic acid. It should be noted that, as described earlier, organic acids may also be used according to the invention instead of inorganic acids for the pickling treatment of the surface that is to be passivated. For example, a citric acid and/or a formic acid may be used as the organic acid.

(15) In an advantageous embodiment of the method, the acid mixture used in the second pretreatment contains at least 1-5 wt % sulphuric acid and/or phosphoric acid besides 95-99 wt % demineralised water. In an acid mixture containing an organic acid, this acid mixture preferably contains 20-30 g/l of the citric acid and/or formic acid in demineralised water mentioned above for exemplary purposes.

(16) Another advantageous variant provides that the acid mixture also contains 50-1000 ppm free fluorides.

(17) In an advantageous further development, it is provided that the surfaces of the cooling line that are to be passivated are rinsed multiple times with demineralised water after the respective pretreatment and/or after the passivation process.

(18) A heat exchanger of such kind according to the invention is produced at least according to the method and/or passivated by means of the abovementioned method.

(19) Of course, the features described in the preceding text are usable not only in each of the combinations described but also in other combinations or alone without departing from the scope of the present invention.