WO2004085707A1

WO2004085707A1 - Aqueous metal finishing solution, methods for finishing metal components, system for cleaning metal components and finished brass products

Info

Publication number: WO2004085707A1
Application number: PCT/US2004/008668
Authority: WO
Inventors: George R Vraciu
Original assignee: Swagelok Co
Current assignee: Swagelok Co
Priority date: 2003-03-21
Filing date: 2004-03-19
Publication date: 2004-10-07
Anticipated expiration: 2005-09-21

Abstract

An improved method of finishing metal components, such as brass fittings, is provided. The method employs a finishing solution comprised generally of an aqueous solution of organic acid, oxidizing agent and oxidation stabilizer. As such, the finishing of the metal component can be carried out in a single process tank and only requires a single set of rinses. The improved method provides a more efficient and economical process, while also providing a chromium-free finishing solution.

Description

A^QUEOUS METAL FINISHING SOLUTION, METHODS FOR FINISHING METAL COMPONENTS, S_YST_EM

FOR CLEANING METAL COMPONENTS AND FINISHED BRASS PRODUC_TS

FIELD OF THE INVENTION

[0001] The invention relates to an improved brass bright dip solution and method for finishing brass components, and more specifically to a chromium-free solution and process for finishing brass components.

BACKGROUND OF THE INVENTION

[0002] Brass components, such as, for example, fittings, are typically finished prior to use or installation by contact with a finishing solution. Such a finishing removes oxides that form along the surfaces of the brass components, thereby reducing corrosion and making the component more stable for clean environments. In addition, depending on the desired aesthetic appearance for the finished brass component, copper or zinc can be dissolved in the finishing solution at a greater rate, thereby leaving a copper-enriched surface or a zinc-enriched surface. If it is desirable to have a yellow-gold appearance, the finishing solution should dissolve copper at a higher rate than zinc, thereby leaving a zinc-enriched surface. If it is desirable to have more of an orange tint, the finishing solution should dissolve zinc at a higher rate than copper, thereby leaving a copper-enriched surface.

[0003] Current techniques are cumbersome, relatively expensive and produce large amounts of waste water that must be treated. Current processes employ three different process tanks, a pre-dip acid tank filled with nitric acid, an acid mix tank filled with a solution of nitric acid, sulfuric acid, and hydrochloric acid, and a brightening or finishing tank filled with a solution of sodium dichromate and sulfuric acid. After each of these process tanks a series of rinse tanks is employed. After rinsing the components, the rinse water must be treated prior to recycling. Furthermore, since the process involves hexavalent chromium, which many European regulations prohibit, it is desirable to eliminate chromium compounds from the finishing solution.

SUMMARY OF THE INVENTION

[0004] An improved brass bight dip solution and method for finishing brass components is provided herein. The brass bight dip solution is a finishing solution that leaves components with an oxide-free surface with a yellow-gold luster. The method and solution of the present invention is a chromium free process. [0005] In one embodiment the finishing solution is an aqueous solution of organic acid, an oxidizing agent, and an oxidization stabilizer. In one particular embodiment, the finishing solution is comprised of an aqueous solution of citric acid, hydrogen peroxide, and a hydrogen peroxide stabilizer.

[0006] Another aspect of the present invention is an improved method of finishing metal components, such as brass fittings. The improved process employs a single processing tank and only one rinse cycle. As such, the improved method employs less rinse water, only one process fluid to create, monitor and control, and provides an easier treatment of the used rinse water.

BRIEF DESCRIPTION OF THE DRAWINGS [0007] The present invention may be more readily understood by reference to the following drawings. While certain embodiments are shown as illustrative examples of the present invention, the scope of this application should not be construed as limited to these illustrative examples.

[0008] Figure 1 is a schematic illustration of a brass finishing process incorporating the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention provides a composition for finishing components, specifically brass components, and an improved method for finishing such components. While the description of the invention is generally directed to brass components, such as, for example, a fitting, other types of components can be finished employing the same solution and process. For example, it is contemplated that the composition and process of the present invention can be employed for finishing various copper alloys, such as, for example, bronze and pewter, zinc alloys, tin alloys, nickel alloys and other such alloys. Furthermore, while the invention is generally described herein as a solution, other compositions are possible, such as, for example, dispersions.

[0010] The finishing solution is generally comprised of an aqueous solution of an organic acid, an oxidizing agent and an oxidant stabilizer. Preferably, the aqueous solution is formed with deionized water. The organic acid can be any mild organic acid such as, for example, gluconic acid, salicylic acid, citric acid, or mixtures thereof. However citric acid is preferred. It is preferable to use an organic acid with a pH in the working range of about 0.75 to about 1.65. In one embodiment, the oxidizing agent is hydrogen peroxide, however other oxidizing agents can be used. Other oxidizing agents that can be used include inorganic acids, such as, for example, nitric acid, sulfuric acid and phosphoric acid. The oxidant stabilizer can be 244 PCM Stabilizer, which is a mixture of p- hydroxy benzenesulfonic acid and sulfuric acid and proprietary ingredients and made by M.F. Good Company, acetanilide, or other comparable components.

[0011] In one embodiment, the finishing solution is comprised of about 150 to about 250 grams per liter organic acid, about 5 to about 8 percent by volume oxidizing agent, about 4 percent to about 7 percent by volume oxidant stabilizer, and the balance water.

[0012] In one particular embodiment, the finishing solution is comprised of an aqueous solution of citric acid, hydrogen peroxide, and 244 PCM Stabilizer. The solution can comprise about 50 to about 300 grams per liter of citric acid, or as much as about 600 grams per liter, about 1.5 percent to about 30 percent by volume hydrogen peroxide, about 2 percent to about 7 percent by volume 244 PCM Stabilizer, and the balance deionized water. Optionally, the 244 PCM Stabilizer can be replaced with about 0.02 to about 0.2 grams per liter of acetanilide. Preferably, the finishing solution comprises about 150 to about 200 grams per liter of citric acid, about 5 percent to about 8 percent by volume hydrogen peroxide, about 4 percent to about 7 percent 244 PCM Stabilizer, and the balance deionized water. More preferably, the solution finishing comprises about 200 grams per liter of citric acid, about 6.5 percent by volume hydrogen peroxide, about 5 percent 244 PCM Stabilizer, and the balance deionized water. The preferred finishing solution mentioned in this disclosure is ideal for creating a bright yellow-gold luster for brass components. By varying the components, such as by providing a solution that dissolves zinc at a higher rate than copper, brass components can be created with an orange luster. For example, this can be achieved by lowering the citric acid below 100 grams per liter or by replacing the citric acid with nitric acid. Furthermore, by using this solution or other solutions made by varying the components, other alloys, such as, for example, bronze or pewter, can also be finished.

[0013] The finishing solution may conveniently be made by adding citric acid, in crystalline form, to deionized water at room temperature. The mixture is then stirred until all the citric acid crystals dissolve. The hydrogen peroxide stabilizer is then added to the solution. Finally the hydrogen peroxide is added. The solution is then mixed to form a homogenous solution. Similar solutions can be made in a similar fashion.

[0014] Figure 1 illustrates a convenient way of finishing brass components with the preferred finishing composition described above. In order to finish the brass components, the components are dropped into the process tank 10 filled with the finishing solution. Optionally, grease, oils, soils, and other contaminants can be removed in an alkaline rinse tank 15 prior to placement of the components into the process tank 10. The finishing solution can be maintained any temperature between its boiling and freezing points, although it is most convenient to operate at room temperature. Preferably the finishing tank operates at a temperature between about 60°F and about 90°F, and it is even more preferable to operate the finishing tank at a temperature between about 70°F and about 80°F. Furthermore, in order to facilitate uniform finishing, one or more tumblers 20 can be placed in the process tank 10. Any type of tumbler can be used provided it tumbles, turns or otherwise agitates the components. The components are submerged in the solution for a time sufficient to remove the oxides, which is typically between about 30 to about 120 seconds, and more typically about 60 seconds, depending on the degree of finishing desired as well as the concentrations of ingredients in the finishing solution.

[0015] After the finishing process is complete, the components are removed from the process tank 10 and rinsed in one or more rinse tanks 30. In one embodiment three counter-flow rinse tanks using deionized water are used, however the number of rinse tanks used can vary depending on the volume, flow, and purity desired. Rinse water from the rinse tanks can directly contact the metal component, thereby avoiding an acid-treatment step. Water from the rise tanks 30 is then transferred to a treatment facility 35 to remove any contaminants prior to recycling of the water. The treatment facility can provide for treatment of the used rinse water in a single step, as opposed to the multiple treatment steps required by the prior art process. The components are then dried, preferably by one or more forced hot air dryers 40.

[0016] If the preferred finishing solution mentioned above is used, the resulting finished product is a brass component with a bright yellow-gold luster. The surface of the brass component is essentially oxide free and is zinc enriched. By employing the method mentioned above, the process of finishing components is greatly simplified, hi comparison to, conventional methods, the time to finish products is greatly reduced. Furthermore, less chemicals and less processing tanks are required. In addition, only one processing solution needs to be monitored and controlled, whereas in conventional methods three different processing solutions must be monitored and controlled. A further advantage of the present invention is the avoidance of highly corrosive acids, such as nitric acid, sulfuric acid and hydrochloric acid, and carcinogenic chromium compounds. An even further advantage is the reduction in the number of rinse cycles, and thus a reduction in the amount of rinse water used and a reduction in the amount of water that must be treated. Also, since the acid employed is less corrosive and there is an absence of chromium compounds, the rinse water treatment process is greatly simplified. [0017] The present invention has been described with reference to the preferred embodiments. However, it should be appreciate that alternations and modifications are possible and that describing each of these alternations or modifications is not possible. As such, it should be appreciated that these alterations are within the scope of the present invention to the extent they fall within the scope of the claims included herewith.

Claims

1. An aqueous finishing solution comprising an organic acid, an oxidizing agent, and an oxidant stabilizer.

2. The finishing solution of claim 1, wherein the organic acid is citric acid, gluconic acid, salicylic acid, or combinations thereof.

3. The finishing solution of claim 1 , wherein the oxidizing agent is hydrogen peroxide.

4. The finishing solution of claim 1, wherein the oxidant stabilizer is 244 PCM Stabilizer, acetanilide, or combinations thereof.

5. The finishing solution of claim 1, wherein the solution is comprised of about 150 to about 250 grams per liter organic acid, about 5 to about 8 percent by volume oxidizing agent, about 2 percent to about 7 percent by volume oxidation stabilizer, and the balance water.

6. The finishing solution of claim 5, wherein the organic acid is citric acid, the oxidizing agent is hydrogen peroxide, and the oxidant stabilizer is 244 PCM Stabilizer.

7. The finishing solution of claim 1, wherein the finishing solution is chromium-free.

8. A method of finishing a metal component, comprising the steps of:

contacting the metal component with an aqueous finishing solution comprising an organic acid, an oxidizing agent, and an oxidant stabilizer.

9. The method of claim 8 further comprising the step rinsing the components with rinse water.

10. The method of claim 8, wherein said solution is chromium-free.

11. The method of claim 8 further comprising the step of drying the components with one or more forced hot air dryers.

12. The method of claim 8 further comprising the step of cleaning the components in an alkaline rinse prior to contacting the components with said finishing solution.

13. The method of claim 8, wherein the component is submerged in the finishing solution, and the method further comprises the step of tumbling the component while submerged in the in the finishing solution.

14. The method of claim 9, wherein the components are rinsed by three counter-flow deionized water rinse tanks.

15. The method of claim 9 further comprising the step of treating the rinse water in a single step.

16. A system for cleaning metal components comprising:

one process tank containing an aqueous solution comprising an organic acid, an oxidizing agent, and an oxidation stabilizer; and

one or more rinse tanks proximate to said process tank.

17. The system of claim 16, wherein said one or more rinse tanks are counter- flow deionized water rinse tanks.

18. The system of claim 16, further comprising one or more force hot air dryers.

19. The system of claim 16, further comprising one or more tumblers located within said process tank.

20. A method for removing oxides from the surface of a metal component to thereby produce a finished metal component comprising the steps of:

(1) contacting the component with an aqueous finishing solution;

(2) directly contacting the component produced in step (1) with rinse water to thereby produce said finished metal component.

21. The method of claim 20, wherein said aqueous solution is comprises an organic acid, an oxidizing agent, and an oxidization stabilizer.

22. A brass product finished by the process comprising the steps of:

contacting the metal component with an aqueous finishing solution comprising an organic acid, an oxidizing agent, and an oxidation stabilizer.

23. A method of finishing a metal component comprising the steps of:

contacting the metal component with a finishing solution, wherein said finishing solution is comprised of an acid with a pH between about 0.75 and about 1.65; and

rising the metal component with rinse water.

24. The method of claim 23 wherein said finishing solution is contained in a single tank.

25. The method of claim 23, wherein the metal component is rinsed by three counter-flow deionized water rinse tanks.

26. The method of claim 23 further comprising the step of treating the rinse water in a single step.

27. The method of claim 23 wherein the metal component is brass.

28. A method of finishing a metal component comprising the steps of:

contacting the metal component with a single finishing solution contained in a single process tank; and

rinsing the metal component with rinse water.

29. The method of claim 28, wherein the metal component is rinsed by three counter-flow deionized water rinse tanks.

30. The method of claim 28 further comprising the step of treating the rinse water in a single step.

31. The method of claim 28 wherein the metal component is brass.