Surface treatment method of aluminum for bonding different materials

Abstract

Disclosed is a method of fabricating an aluminum alloy member for bonding different materials. The method may include etching the aluminum alloy member with one or more etching solutions, and forming one or more undercuts on a surface of the aluminum alloy member.

Claims

1. A method of fabricating an aluminum alloy member, comprising: etching a surface of the aluminum alloy member using one or more etching solutions; and forming one or more undercuts on the surface of the aluminum alloy member, wherein the one or more undercuts are formed by: a first etching of immersing the aluminum alloy member in an CrO.sub.3 aqueous solution; a second etching of immersing the aluminum alloy member in an FeCl.sub.3 aqueous solution; and a third etching of immersing the aluminum alloy member in an HCl aqueous solution.

2. The method of claim 1, wherein the first etching comprises immersing the aluminum alloy member in the CrO.sub.3 aqueous solution of at a temperature of about 20 to 30 C.

3. The method of claim 2, wherein the first etching comprises immersing the aluminum alloy member in the CrO.sub.3 aqueous solution for about 3 minutes.

4. The method of claim 2, wherein the CrO.sub.3 aqueous solution has a concentration of CrO.sub.3 of about 150 g/l to 200 g/l.

5. The method of claim 1, wherein the second etching comprises immersing the aluminum alloy member in the FeCl.sub.3 aqueous solution of a temperature of about 20 to 30 C.

6. The method of claim 5, wherein the second etching comprises immersing the aluminum alloy member in the FeCl.sub.3 aqueous solution for about 0.5 to 1 minutes.

7. The method of claim 5, wherein the FeCl.sub.3 aqueous solution has a concentration of FeCl.sub.3 of about 50 g/l-150 g/l.

8. The method of claim 1, wherein the third etching comprises immersing the aluminum alloy member in the HCl aqueous solution of a temperature of about 20 to 30 C.

9. The method of claim 8, wherein the third etching comprises immersing the aluminum alloy member in the HCl aqueous solution for about 0.5-1 minutes.

10. The method of claim 8, wherein the HCl aqueous solution has a concentration of HCl of about 50 g/l to 150 g/l.

11. The method of claim 1, further comprising coating TiO.sub.2 powder on the one or more undercuts.

12. The method of claim 11, wherein the coating the TiO.sub.2 powder comprises immersing the aluminum alloy member in an TiO.sub.2 aqueous solution comprising the TiO.sub.2 powder.

13. The method of claim 12, wherein the TiO.sub.2 aqueous solution has a concentration of the TiO.sub.2 powder of about 20 mg/l.

14. The method of claim 13, wherein the coating the TiO.sub.2 powder comprises immersing the aluminum alloy member in the TiO.sub.2 aqueous solution at a temperature of about 20 to 30 C.

15. The method of claim 14, wherein the coating the TiO.sub.2 powder comprises immersing the aluminum alloy member in the TiO.sub.2 aqueous solution for about 0.5 to 1 minutes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 is a flow chart of an exemplary surface treatment method of fabricating an aluminum alloy member for bonding different materials according an exemplary embodiment of the present invention;

(3) FIG. 2 illustrates an exemplary bonding of resin and an aluminum alloy member according to an exemplary embodiment of the present invention;

(4) FIG. 3 shows an example surface-treated according to an exemplary embodiment of the present invention;

(5) FIG. 4 shows an exemplary test piece for evaluation of adhesion according to an exemplary embodiment of the present invention;

(6) FIG. 5A is a photograph of an exemplary surface of the aluminum alloy member from plasma coating (conventional method), and FIG. 5B is a photograph of an exemplary surface of the aluminum alloy member from immersion coating according to an exemplary embodiment of the present invention.

(7) FIG. 6 shows images of adhesion and surface organization according to etching by steps.

DETAILED DESCRIPTION

(8) The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term and/or includes any and all combinations of one or more of the associated listed items.

(9) Unless specifically stated or obvious from context, as used herein, the term about is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. About can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term about.

(10) It is understood that the term vehicle or vehicular or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

(11) In order to fully understand the present invention, the operational advantages of the present invention, and the objects attained by the practice of the present invention, reference should be made to the appended drawings illustrating the preferred embodiments of the invention and the description in the accompanying drawings.

(12) In describing a preferred exemplary embodiment of the present invention, known techniques or repetitive descriptions that may unnecessarily obscure the essence of the present invention would either reduce or omit the description thereof.

(13) FIG. 1 shows an exemplary flow chart of an exemplary surface treatment method of fabricating an aluminum alloy member for bonding different materials by the present invention.

(14) For example, the surface treatment method o may include i) forming one or more undercuts or structures formed underneath the surface of an aluminum alloy member by the steps of degreasing S10, surface treatment S20, powder coating S30 and cleaning S40, as shown in FIG. 2, and ii) coating a powder on the undercut shape to bond the plastic resin to the adhesive surface.

(15) The degreasing S10 may be a step to remove the oil layer which inhibits the surface treatment of the aluminum alloy member and is carried out with Na.sub.3PO.sub.4 aqueous solution.

(16) For example, the Na.sub.3PO.sub.4 aqueous solution may have a concentration of about 20 g/l to 40 g/l, and the operating condition may be 0.5 to 3 minutes of cathode degreasing at current density of about 1 to 4 A/dm and voltage of about 4 to 6V.

(17) The surface treatment step S20 may include the step of etching surface of the aluminum alloy member by three steps.

(18) The primary etching step may include immersing the aluminum alloy member in an aqueous solution of CrO.sub.3 and corroding the aluminum component of the surface.

(19) The CrO.sub.3 may be included in an aqueous solution at a concentration of about 150 g/l to 200 g/l, and the operating condition is a condition for immersing at a temperature of about 20 to 30 C. for about 3 minutes.

(20) The secondary etching step may include immersing the aluminum alloy member in FeCl.sub.3 aqueous solution and corroding the Si component of the aluminum base material.

(21) The FeCl.sub.3 may be included in an aqueous solution at a concentration of about 50 g/l to 150 g/l, and the operating condition is a condition of immersing at a temperature of about 20 to 30 C. for about 0.5-1 minutes.

(22) The tertiary etching step may include immersing the aluminum alloy member in an HCl aqueous solution, for example, to corrode again the aluminum component deeper through the penetration etching after FeCl.sub.3 treatment and to corrode faster than the first etching step.

(23) The HCl may be included in the aqueous solution in an amount of about 50 g/l to 150 g/l, and the operating condition is a condition of immersing at a temperature of about 20 to 30 C. for about 0.5 to 1 minutes.

(24) By the step S20 of the surface treatment by the three steps etching, as shown in FIG. 3, hook-shaped undercuts may be formed on the bonding surface of the aluminum alloy member, and these undercuts may be immersed in a solution containing TiO.sub.2 powder to perform powder coating S30.

(25) For example, by forming a hook-shaped undercut by the primary surface etching, the secondary undercut etching and the tertiary penetration etching as shown in the FIGS., a higher adhesion may be secured.

(26) FIG. 6 summarizes the images of adhesion and surface organization according to etching by steps.

(27) Furthermore, the present invention does include a coating layer including SiO.sub.2 powder, but instead, includes TiO.sub.2 as a powder.

(28) When the SiO.sub.2 powder is used, the adhesion may be weaken at pH of weak alkali or acid. However, according to exemplary embodiments of the present invention, when the TiO.sub.2 powder is used, the TiO.sub.2 powder may be more suitable because of its low reaction with water and greater thermal stability than SiO.sub.2.

(29) As shown in FIG. 3, because the TiO.sub.2 powder exists between resin and aluminum so that not only the surface area is widened to increase the adhesion but also flame resistance and corrosion resistance may be substantially improved, thereby maintaining the bonding force even in a high temperature and high humidity environment.

(30) In addition, because the powder should be coated on the undercut shape, in the present invention, the coating layer may be well formed to the undercuts by coating the powder by the immersion method without using the plasma method, thereby contributing to the bonding performance.

(31) The resulting bonding performance will be described later.

(32) The TiO.sub.2 powder was included in an aqueous solution in an amount of 20 mg/l, and it is preferable to immerse at a temperature of about 20 to 30 C. for about 0.5-1 minutes.

(33) In this condition, when the powder may be dipped and then dried, the powder may settle to the surface.

(34) After the powder coating, the aluminum surface treatment may be completed when immersing in a solution containing ethylene at a temperature of about 20 to 30 C. for about 1 minute and cleaning S40.

(35) The bonding performance of the aluminum surface treatment method by the above-described composition and method was verified using a tensile tester.

(36) FIG. 4 is an example of producing a test piece, in which an A6063 aluminum alloy member having a size of 45 mm18 mm2 mm was bonded to a plastic member (PA6-GF60% resin) having a size of 40 mm10 mm3 mm, and the bonding area was 10 mm5 mm, and then, the experiment was performed.

(37) Table 1 shows the test results for TiO.sub.2 compared to SiO.sub.2, and Table 3 shows the test results for coating TiO.sub.2 powder.

(38) As can be seen from the tables, adhesion at the high temperature may be substantially improved when TiO.sub.2 is applied compared to where SiO.sub.2 is applied, or nothing is applied. Moreover, the high temperature adhesion may be substantially improved when immersion coating is applied compared to the case that plasma coating is performed, or nothing is performed.

(39) TABLE-US-00001 TABLE 1 Division SiO.sub.2 TiO.sub.2 Not applied Water reaction Existence(softening) None room temperature 30 40 30 adhesion (MPa) High temperature 10 30 10 adhesion (containing moisture, MPa)

(40) TABLE-US-00002 TABLE 2 Division Plasma coating Immersion coating Not applied room temperature 30 40 30 adhesion (MPa) High temperature 10 30 10 adhesion (containing moisture, MPa)

(41) FIG. 5A is a surface photograph of the case of plasma coating, and FIG. 5B is a surface photograph of case of immersion coating.

(42) As shown in FIG. 5A and FIG. 5B, TiO.sub.2 particles are hardly visible when plasma coating and TiO.sub.2 particles are confirmed in immersion coating.

(43) Likewise, bonding performance as shown in Table 2 is demonstrated.

(44) Although the present invention has been described with reference to the drawings, it will be apparent to those skilled in the art that the invention is not limited to the exemplary embodiments set forth herein but that various modifications and variations can be made therein without departing from the spirit and scope of the present invention.

(45) Accordingly, such modifications or exemplary variations should fall within the scope of the claims of the present invention, and the scope of the present invention should be construed on the basis of the appended claims.