Corrosion-resistant vehicle bracket and method for manufacturing the same

Abstract

The vehicle bracket according to the present disclosure comprises a base steel plate and a hot-dip Zn-Al-Mg plating layer formed on the base steel plate, with one or more cut surfaces formed thereon, and an anti-rust coating layer formed on the cut surfaces and the plating layer, the anti-rust coating layer being formed by immersion in an anti-rust coating liquid containing a metal coating liquid containing a metal nitrate and a surfactant in a mass ratio of 2 to 3:1.

Description

Technical Field

[0001] The present disclosure relates to a vehicle bracket and a method for manufacturing the same. More specifically, the present disclosure relates to a vehicle bracket having a cut surface with improved corrosion resistance and a method for preventing rust of the bracket.

Background Art

[0002] Since cold-rolled steel sheet (SPCC) has high formability and workability, bending, pressing, and drawing are easy, so it is widely used as parts such as vehicle brackets.

[0003] Although cold-rolled steel sheet has high formability and workability, it oxidizes very easily when the oxide film peels off, and the cold-rolled steel sheet may rust depending on the storage conditions. Therefore, the cold-rolled steel sheet is mainly subjected to zinc plating or painting.

[0004] On the other hand, vehicle brackets are exposed to moisture and affected by the outside air, so a high level of corrosion resistance is required. Therefore, the formation process of the zinc plating layer and painting are performed separately.

[0005] Vehicle brackets are manufactured in various shapes. The WSS bracket for supporting the EPB cable has two or more cut surfaces and curves, and is mainly manufactured by applying zinc plating to the surface of the cold-rolled steel sheet to form a plating layer, and then pressing this cold-rolled steel sheet into the shape of the bracket.

[0006] In this case, due to the pressing process, an exposed portion of the base steel sheet is formed into a complex cut surface, and the plating layer is damaged, resulting in a problem that the corrosion resistance of the entire bracket is reduced. This problem also affects the durability of the vehicle.

[0007] Therefore, there is an urgent need to develop a vehicle bracket with improved corrosion resistance.

[0008] As background technology to this disclosure, Patent Document 1 discloses a fixing bracket for assembling a vehicle fender panel. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Patent Application Publication No. 10-2005-0089568 [Overview of the project] [Problems that the invention aims to solve]

[0010] The purpose of this disclosure is to provide a vehicle bracket having a cross-section with improved corrosion resistance.

[0011] Another object of this disclosure is to provide a method for manufacturing a vehicle bracket that can improve corrosion resistance by using press working to form a rust-preventive coating layer as a sealing film over the entire cut surface and the entire outer surface of the vehicle bracket having a cut surface.

[0012] All of the above and other purposes of this disclosure can be achieved by the disclosure described below. [Means for solving the problem]

[0013] 1. One aspect of this disclosure relates to a vehicle bracket.

[0014] The vehicle bracket comprises a base steel plate and a hot-dip Zn-Al-Mg plating layer formed on the base steel plate, with one or more cut surfaces formed thereon, and a rust-preventive coating layer formed on the cut surfaces and the plating layer, and the rust-preventive coating layer is formed by immersion in a rust-preventive coating solution containing a metal coating solution containing a metal nitrate and a surfactant in a mass ratio of 2 to 3:1.

[0015] 2. In Specific Example 1, the molten Zn-Al-Mg plating layer may contain 1.5 to 3.0% by weight of Zn, 1.5 to 2.5% by weight of Al, 1.5 to 2.5% by weight of Mg, and the remainder being unavoidable impurities.

[0016] 3. In specific example 1 or 2, the metal coating solution may contain 3 to 5% by weight of aluminum nitrate, 5 to 10% by weight of silicon dioxide, and the remainder being water.

[0017] 4. In any one of the specific examples 1 to 3, the surfactant may contain 3 to 5% by weight of sodium sulfate and the remainder being water.

[0018] 5. In any one of the specific examples 1 to 4, it is possible to prevent the formation of red rust in a salt spray test using a 5% salt concentration, a salt spray rate of 1.5 ml / h, and continuous spraying conditions of 740 hours or more.

[0019] 6. In any one of the specific examples 1 to 5, it is not necessary for a paint layer to be formed on the rust-preventive coating layer.

[0020] 7. Another aspect of this disclosure relates to a method for manufacturing a vehicle bracket.

[0021] The method for manufacturing the vehicle bracket comprises (a) the step of manufacturing an alloy steel sheet containing a molten Zn-Al-Mg plating layer, (b) the step of press-forming the alloy steel sheet to manufacture a bracket shape, and (c) the step of immersing the bracket in a rust-preventive coating liquid to form a rust-preventive coating layer, wherein the rust-preventive coating liquid contains a metal coating liquid containing a metal nitrate and a surfactant in a mass ratio of 2 to 3:1.

[0022] 8. In specific example 7, the metal coating solution may contain 3-5% by weight of aluminum nitrate, 5-10% by weight of silicon dioxide, and the remainder being water.

[0023] 9. In specific examples 7 or 8, the surfactant may contain 3-5% by weight of sodium sulfate and the remainder being water.

[0024] 10. In any one of Specific Examples 7 to 9, in step (c), the rust preventive coating liquid can be maintained at 40 to 60°C.

[0025] 11. In any one of Specific Examples 7 to 10, in step (c), the rust preventive coating liquid can be maintained at pH 3.0 to 4.0.

[0026] 12. In any one of Specific Examples 7 to 10, in step (c), the dipping time may be 50 to 70 seconds.

Advantages of the Invention

[0027] According to the vehicle bracket according to the present disclosure, even in the case of a complex structure having one or more cut surfaces, a rust preventive coating layer can be added on the upper part of the cut surface, so that the entire plating layer does not corrode. As a result, the corrosion resistance is significantly enhanced.

[0028] According to the vehicle bracket according to the present disclosure, the surface hardness can be increased by using a Zn-Al-Mg ternary plated steel sheet with high corrosion resistance, and an additional rust preventive coating layer can be formed on the cut surface, thereby significantly improving the corrosion resistance.

[0029] According to the manufacturing method of the vehicle bracket according to another aspect of the present disclosure, there is no need to form a separate plating layer and an additional coating layer. Furthermore, the corrosion resistance can be enhanced in a single step of forming a rust preventive coating layer on the outer surface of the Zn-Al-Mg ternary plated steel sheet, thereby significantly improving the efficiency of the manufacturing process of the vehicle bracket.

Brief Description of the Drawings

[0030] [Figure 1] FIG. 1 is a schematic view of a vehicle bracket according to a specific example of the present disclosure. [Figure 2] FIG. 2 is a process flow diagram of a manufacturing method of a vehicle bracket according to another aspect of the present disclosure. [Figure 3]Figure 3 shows scanning electron microscope images of a vehicle bracket having a rust-preventive coating layer and a vehicle bracket without a rust-preventive coating layer, which are specific examples of the present disclosure. [Figure 4] Figure 4 shows photographs of a vehicle bracket according to a specific example of this disclosure, showing the results of salt spray time. [Modes for carrying out the invention]

[0031] The following description of this disclosure will be made more specifically with reference to the attached drawings. However, the following drawings are provided solely to facilitate understanding of this disclosure, and this disclosure is not limited to these drawings. Furthermore, the shapes, sizes, proportions, angles, numbers, etc., shown in the drawings are provided only as examples, and this disclosure is not limited to what is shown in the drawings.

[0032] Throughout this specification, the same reference numerals indicate the same components. Furthermore, specific descriptions of known related technology are omitted in this disclosure if such specific descriptions are deemed likely to unnecessarily obscure the subject matter of this disclosure.

[0033] As used herein, the terms “equip,” “possess,” or “include,” unless used with the term “only,” may imply the addition of other components. Unless otherwise specified, singular expressions used herein are intended to include plural expressions.

[0034] Unless otherwise explicitly stated, the analysis of the components shall be interpreted as including a margin of error.

[0035] When describing the positional relationship between two components using terms such as "above," "above," "below," or "beside," if the terms "immediately" or "directly" are not used, it is possible that one or more components are located between these two components.

[0036] The positional relationships of terms such as "top," "top surface," "bottom," and "bottom surface" are based on the drawings and do not represent absolute positional relationships. In other words, the positions of "top," "top surface," "bottom," and "bottom surface" may change depending on the observation position.

[0037] In this specification, the numerical range "a~b" is defined as "≥a and ≤b".

[0038] The vehicle bracket relating to a specific example of this disclosure will be described in detail below with reference to the drawings.

[0039] Figure 1 is a schematic diagram of a vehicle bracket relating to a specific example of the present disclosure.

[0040] Referring to Figure 1, the vehicle bracket includes a base steel plate 100, a plating layer 200, and a rust-preventive coating layer 300.

[0041] The base steel sheet 100 may include a steel sheet that can be plated with a hot-dip galvanizing layer. In particular, the base steel sheet 100 may be a cold-rolled steel sheet.

[0042] If the base steel plate 100 is a cold-rolled steel plate, the plating layer has a uniform thickness and a clean surface so that the hot-dip galvanized layer can be easily formed.

[0043] If the base steel plate 100 is a hot-rolled steel plate, the oxide layer is formed by heat treatment, making it difficult to form a separate plating layer on the upper surface of the base steel plate 100. Furthermore, since the oxide layer itself has corrosion-resistant properties, an additional plating process is unnecessary.

[0044] The molten Zn-Al-Mg plating layer 200 may be formed by melting the metallic elements on the base steel plate 100.

[0045] Specifically, a binary eutectic structure of Zn-MgZn2 and a ternary eutectic structure of Zn-Al-MgZn2 may be formed. In the process structure of Zn-MgZn2, MgZn2 dissolves more actively, improving the corrosion resistance of the cut surface, so a large amount of binary eutectic structure is formed, which is preferable. In the specific example of this disclosure, since the anti-corrosion coating layer is formed not only on the upper surface of the coating layer but also on the cut surface, it is not necessary to adjust the Zn-Al-Mg composition in the plating bath to form a large amount of binary eutectic structure.

[0046] In a specific example, the molten Zn-Al-Mg plating layer 200 may contain Zn: 1.5-3.0% by weight, Al: 1.5-2.5% by weight, Mg: 1.5-2.5% by weight, and the remainder being unavoidable impurities.

[0047] Within the content range, a binary eutectic structure of Zn-MgZn2 and a ternary eutectic structure of Zn-Al-MgZn2 can be formed. When the plating layer is exposed to a corrosive environment, MgZn2 has a lower corrosion potential than Zn, so MgZn2 is the first to dissolve in the corrosive environment. The dissolved Mg forms Mg(OH)2, which reduces the alkalinity of the cathode region, and thus a stable Zn5(OH)8Cl2H2O is formed, improving corrosion resistance.

[0048] The vehicle bracket has one or more cut surfaces, and the anti-corrosion coating layer is formed on the cut surfaces and the plating layer.

[0049] When a cut surface is formed, the molten Zn-Al-Mg plating layer 200 may be removed, which can degrade the corrosion resistance. However, since the rust-preventive coating layer 300 is formed on top of the cut surface, the corrosion resistance of the cut surface can be significantly improved.

[0050] If the rust-preventive coating layer 300 is not formed on the upper part of the cut surface, corrosion such as white rust or red rust may occur in a corrosive environment.

[0051] The rust-preventive coating layer 300 is formed by immersing it in a rust-preventive coating solution containing a metal coating solution containing metal nitrates and a surfactant in a mass ratio of 2 to 3:1.

[0052] The rust-preventive coating layer 300 is formed by immersing the material in a rust-preventive coating solution containing a metal coating solution and a surfactant, and then drying it.

[0053] When the rust-preventive coating solution contains a metal coating solution containing metal nitrates within the above range and a surfactant, the degree of dispersion of the metal nitrates in the rust-preventive coating solution can be increased, allowing the rust-preventive coating layer to be formed by immersion alone. Furthermore, the thickness of the rust-preventive coating layer can be made uniform, and the metal coating solution can be deposited onto the plating layer with high durability.

[0054] In a specific example, the metal coating solution may contain 3-5% by weight of aluminum nitrate, 5-10% by weight of silicon dioxide, and the remainder being water.

[0055] When the metal coating solution contains aluminum nitrate within the above range, a fine crystalline structure can be formed, and as a result, not only the corrosion resistance of the rust-preventive coating layer but also its hardness can be effectively enhanced.

[0056] Silicon dioxide can effectively enhance the corrosion resistance of magnesium-containing alloy layers. Within the above range, not only corrosion resistance but also wear resistance can be improved, and as a result, the hardness of the rust-preventive coating layer can be increased.

[0057] In specific examples, the surfactant may contain 3-5% by weight of sodium sulfate and the remainder being water.

[0058] Sodium sulfate is an anionic surfactant. Within the above range, it can stabilize the crystalline structure of aluminum nitrate, thereby improving its corrosion resistance.

[0059] In a salt spray test using a 5% salt solution concentration, a salt spray rate of 1.5 ml / h, and continuous spraying conditions for 740 hours or more, it is possible to prevent the formation of red rust on the vehicle bracket 1000.

[0060] Vehicle bracket 1000 has significantly improved corrosion resistance; therefore, in a continuous salt spray test lasting more than 740 hours, for example, even when salt water is sprayed continuously for 741 hours at a 5% salt concentration and a salt water spray rate of 1.5 ml / h, no red rust is formed. Thus, corrosion resistance can be greatly improved.

[0061] In the specific example, a paint layer does not need to be formed on top of the rust-preventive coating layer 300.

[0062] The plating layer of the vehicle bracket 1000 does not have a separate paint layer formed on it, and rust-preventive paint can be substituted with the rust-preventive coating layer 300.

[0063] The rust-preventive coating layer 300 is colored a darker gray compared to the plating layer, which allows for visual determination of whether or not the rust-preventive coating layer has been formed.

[0064] Another aspect of this disclosure relates to a method for manufacturing a vehicle bracket.

[0065] Figure 2 is a process flow diagram of a method for manufacturing a vehicle bracket according to another aspect of the present disclosure.

[0066] Referring to Figure 2, the method for manufacturing a vehicle bracket includes the steps of (a) manufacturing an alloy steel sheet containing a molten Zn-Al-Mg plating layer, (b) press-forming the alloy steel sheet to manufacture a bracket shape, and (c) immersing the bracket in a rust-preventive coating solution to form a rust-preventive coating layer.

[0067] First, hot-dip galvanized steel sheets are manufactured (S100).

[0068] The hot-dip galvanized steel sheet may be an alloy steel sheet formed by creating a hot-dip Zn-Al-Mg plating layer on top of a base steel sheet.

[0069] The bracket shape is manufactured by press-forming alloy steel sheets (S200).

[0070] The shape of the vehicle bracket can be determined by press forming, and one or more cross-sections can be formed.

[0071] The molten Zn-Al-Mg plating layer can be removed from the cut surface. In this case, the iron component of the base steel plate may be exposed.

[0072] This method may include a step (S210) of degreasing the vehicle bracket.

[0073] The degreasing step removes any oily substances remaining on top of the plating layer, allowing the anti-corrosion coating layer to adhere securely.

[0074] This method may include a step (S220) of cleaning the vehicle bracket after the degreasing step.

[0075] In the step of cleaning the vehicle bracket, foreign matter on the surface can be removed beforehand.

[0076] The rust-preventive coating layer is formed by immersing the bracket in a rust-preventive coating solution (S300).

[0077] The rust-preventive coating solution may contain a metal coating solution containing metal nitrates and a surfactant in a mass ratio of 2 to 3:1.

[0078] The rust-preventive coating solution can be prepared by mixing a metal coating solution within the above range with a surfactant, and a rust-preventive coating layer can be formed by adjusting the immersion conditions. By stabilizing the crystalline structure of the rust-preventive coating layer, the durability of the rust-preventive coating layer can be improved.

[0079] In a specific example, the metal coating solution may contain 3-5% by weight of aluminum nitrate, 5-10% by weight of silicon dioxide, and the remainder being water.

[0080] The metal coating solution contains aluminum nitrate, and a fine crystalline structure is formed on the rust-preventive coating layer, which improves corrosion resistance and can also increase the hardness of the rust-preventive coating layer.

[0081] In specific examples, the surfactant may contain 3-5% by weight of sodium sulfate and the remainder being water.

[0082] The surfactant may contain sodium sulfate and can be used to prepare a rust-preventive coating solution. The metal coating solution can be dispersed to stabilize its crystalline structure.

[0083] In step S300, the rust-preventive coating solution can be maintained at 40-60°C.

[0084] For example, the temperature is preferably 50-60°C, more preferably 50°C.

[0085] Because the rust-preventive coating liquid is maintained within this temperature range, the vehicle bracket can be uniformly coated by immersion.

[0086] In S300, the rust-preventive coating solution can be maintained at a pH of 3.0 to 4.0.

[0087] Specifically, a pH of 3.6 to 4.0 is preferred, and a pH of 4.0 is more preferred.

[0088] By forming a rust-preventive coating layer uniformly within this pH range, surface smoothness can be improved. If the pH exceeds the above range, precipitation may occur in the metal coating solution.

[0089] Within this pH range, the color of the rust-preventive coating can be dark. For example, the rust-preventive coating can be dark gray.

[0090] In S300, the immersion time may be 50 to 70 seconds.

[0091] When immersion is performed within this time range, the thickness of the rust-preventive coating layer can be made uniform, and the average illuminance can be reduced, allowing for the formation of a smooth surface on the vehicle bracket.

[0092] After immersion, the vehicle brackets are recovered and dried at room temperature, thereby manufacturing vehicle brackets with a rust-preventive coating layer.

[0093] According to the vehicle bracket of this disclosure, a bracket shape having one or more cut surfaces is manufactured by press-forming a base steel plate having a hot-dip Zn-Al-Mg plating layer with high corrosion resistance, and then a rust-preventive coating layer is formed on the cut surface and the upper surface of the plating layer. This significantly improves corrosion resistance and also increases hardness.

[0094] High corrosion resistance can be ensured simply by immersing the vehicle bracket in a rust-preventive coating solution to form a rust-preventive coating layer, and then drying the vehicle bracket. Therefore, there is no need to perform a separate painting process to address color changes in the vehicle bracket after painting, which significantly improves the manufacturing efficiency of the vehicle bracket.

[0095] Examples are provided below to aid in understanding this disclosure. However, these examples are illustrative only, and the scope of this disclosure is not limited to the following embodiments.

[0096] Example 1. Manufacturing of a vehicle bracket

[0097] A hot-dip galvanized steel sheet (alloy layer of Zn: 1.5 wt%, Mg: 1.5 wt%, Al: 1.5 wt%) was manufactured, and the hot-dip galvanized steel sheet was cut using a press to produce the shape of a vehicle bracket.

[0098] Vehicle brackets with cut surfaces were degreased, washed twice, and then immersed in a tank containing a rust-preventive coating solution.

[0099] A metal coating solution containing 5% by weight aluminum nitrate, 10% by weight silicon dioxide, and 85% by weight water was prepared, and a surfactant containing 5% by weight sodium sulfate and 95% by weight water was prepared.

[0100] A rust-preventive coating solution containing 25% by weight of surfactant and 75% by weight of metal coating solution was prepared and added to the plating tank.

[0101] After determining whether the rust-preventive coating solution had a pH of 4.0 and adjusting its temperature to 50°C, a vehicle bracket with a cut surface was immersed in the rust-preventive coating solution in the plating tank for 60 seconds.

[0102] The vehicle brackets were collected, washed twice, and dried at room temperature (25°C) for more than 24 hours to obtain the vehicle brackets with the rust-preventive coating layer.

[0103] Experimental Example 1. Identification of rust-preventive coating layers

[0104] Figure 3 shows scanning electron microscope images of a vehicle bracket having a rust-preventive coating layer and a vehicle bracket without a rust-preventive coating layer, which are specific examples of the present disclosure.

[0105] Referring to Figure 3, as shown in Figure 3A, when no rust-preventive coating layer is formed, the surface illuminance increases and becomes uneven. On the other hand, as shown in Figure 3B, when a rust-preventive coating layer is formed on the upper surface of the plating layer, the rust-preventive coating layer adheres durablely to the upper surface of the plating layer, resulting in a smooth surface and a stable crystalline structure of the rust-preventive coating layer.

[0106] Experimental Example 2. Composition of rust-preventive coating solution

[0107] [Table 1]

[0108] Table 1 shows the determination of the shape of the rust-preventive coating layer based on the composition of the rust-preventive coating solution.

[0109] Referring to Table 1, it can be seen that in Example 1, a smooth rust-preventive coating layer with high smoothness is formed. On the other hand, in Comparative Example 1, when the content of the metal coating liquid is reduced compared to the example, almost no rust-preventive coating layer is formed by immersion alone. In Comparative Example 2, because the amount of metal coating liquid after immersion is large, the thickness of the rust-preventive coating layer is uneven, the smoothness is low, and as a result, an additional painting process is required.

[0110] Experimental Example 3. Salt spray test

[0111] A salt spray test was conducted to determine the corrosion resistance of the vehicle bracket manufactured according to the embodiment.

[0112] According to the conditions of KS D 9502, the salinity was 5%, the pH was 6.7, the temperature during the test was 35°C, the spraying method was continuous spraying, and the spray pressure was 1.0 kg / cm². 2 The salt spray rate was adjusted to 1.5 ml / h.

[0113] Using a salt spray tester (VT ST-200), salt water was sprayed onto the vehicle bracket manufactured according to Example 1 at an angle of 15 to 30°.

[0114] Figure 4 shows photographs of a vehicle bracket according to a specific example of this disclosure, showing the results of salt spray time.

[0115] Results from spraying saltwater for a total of 741 hours showed that white rust formed on the vehicle bracket according to the embodiment after 429 hours. On the other hand, no red rust formed even after spraying saltwater for more than 741 hours, indicating that it exhibits very high corrosion resistance. In particular, no red rust formed on the cut surface.

[0116] Therefore, the vehicle bracket according to this disclosure has a rust-preventive coating layer formed on it, and its corrosion resistance and surface hardness are greatly improved. As a result, this vehicle bracket can be used as a WSS bracket for supporting EPB cables used in environments where corrosion and vibration are present. In particular, the corrosion resistance of the cut surface can be improved, and the corrosion resistance and hardness can be greatly improved for WSS brackets with more complex shapes than simple hot-dip galvanized steel plates.

[0117] The embodiments of this disclosure have been described above. Those skilled in the art will understand that modifications can be made without departing from the essential features of this disclosure. Therefore, the disclosed embodiments should be considered illustrative and not restrictive. The scope of this disclosure is defined not by the foregoing but by the claims, and all equivalent differences should be construed as being within the scope of this disclosure. This application relates to the invention described in the claims, but the disclosure of this application also includes: 1. Base steel plate and The base steel plate comprises a molten Zn-Al-Mg plating layer formed on the base steel plate, One or more cross-sections are formed, A rust-preventive coating layer is formed on the cut surface and the plating layer. A vehicle bracket in which the rust-preventive coating layer is formed by immersing the bracket in a rust-preventive coating solution containing a metal coating solution containing a metal nitrate and a surfactant in a mass ratio of 2 to 3:1. 2. The vehicle bracket according to 1., wherein the molten Zn-Al-Mg plating layer contains 1.5 to 3.0% by weight of Zn, 1.5 to 2.5% by weight of Al, 1.5 to 2.5% by weight of Mg, and the remainder being unavoidable impurities. 3. The vehicle bracket according to 1., wherein the metal coating liquid contains 3 to 5% by weight of aluminum nitrate, 5 to 10% by weight of silicon dioxide, and the remainder being water. 4. The vehicle bracket according to 1., wherein the surfactant contains 3-5% by weight of sodium sulfate and the remainder is water. 5. The vehicle bracket described in 1. above, which does not produce red rust in a salt spray test using a 5% salt concentration, a salt spray rate of 1.5 ml / h, and continuous spraying conditions for 740 hours or more. 6. The vehicle bracket according to 1. above, wherein no paint layer is formed on the rust-preventive coating layer. 7. In a method for manufacturing a vehicle bracket, (a) A step of manufacturing an alloy steel sheet containing a molten Zn-Al-Mg plating layer, (b) The step of press-forming the alloy steel sheet to manufacture the bracket shape and (c) The bracket is immersed in a rust-preventive coating liquid to form a rust-preventive coating layer, A method for manufacturing a vehicle bracket, wherein the rust-preventive coating liquid contains a metal coating liquid containing a metal nitrate and a surfactant in a mass ratio of 2 to 3:1. 8. The method according to 7., wherein the metal coating solution contains 3 to 5% by weight of aluminum nitrate, 5 to 10% by weight of silicon dioxide, and the remainder being water. 9. The method according to 7., wherein the surfactant contains 3 to 5% by weight of sodium sulfate and the remainder is water. 10. The method according to 7., wherein in step (c), the rust-preventive coating liquid is maintained at 40 to 60°C. 11. The method according to 7., wherein in step (c), the rust-preventive coating solution is maintained at a pH of 3.0 to 4.0. 12. The method according to 7., wherein in step (c), the immersion time is 50 to 70 seconds. [Explanation of symbols]

[0118] 1000 Vehicle Bracket 100 base steel plate 200 Plating layer 300 Anti-corrosion coating layer

Claims

1. In a method for manufacturing a vehicle bracket, (a) A step of manufacturing an alloy steel sheet containing a molten Zn-Al-Mg plating layer, (b) The step of press-forming the alloy steel sheet to manufacture a bracket shape and (c) The vehicle bracket is immersed in a rust-preventive coating liquid to form a rust-preventive coating layer, The aforementioned rust-preventive coating liquid contains a metal coating liquid containing a metal nitrate and a surfactant in a mass ratio of 2 to 3:

1. The metal coating solution contains 3 to 5% by weight of aluminum nitrate, 5 to 10% by weight of silicon dioxide, and the remainder is water. The surfactant contains 3 to 5% by weight of sodium sulfate and the remainder being water. A method for manufacturing vehicle brackets.

2. The method according to claim 1, wherein in step (c), the rust-preventive coating liquid is maintained at 40 to 60°C.

3. The method according to claim 1, wherein in step (c), the rust-preventive coating solution is maintained at a pH of 3.0 to 4.

0.

4. The method according to claim 1, wherein in step (c), the immersion time is 50 to 70 seconds.

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