[Invention Title]

ANTI CORROSION TREATING CAR BRACKET AND PREPARING METHOD

THEREOF

[Technical Field]

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

[Background Art]

[2] A cold-rolled steel plate (SPCC) is widely used as a component such as a vehicle bracket because the cold-rolled steel plate has high formability and processability and thus is easy to bend, press, and draw.

[3] The cold-rolled steel plate has high formability and processability but is very easily oxidized when an oxidation film is separated, and the cold-rolled steel plate may be rusted in accordance with a storage state. Therefore, the cold-rolled steel plate is primarily galvanized and painted.

[4] Meanwhile, a vehicle bracket is exposed to moisture and affected by outside air and thus requires a high level of corrosion resistance. Therefore, the process of forming a galvanized layer and the painting are separately performed.

[5] The vehicle brackets are manufactured in various shapes. A WSS bracket for supporting an EPB cable includes two or more cut surfaces and curves and is mainly manufactured by galvanizing a surface of the cold-rolled steel plate to form a plating layer and then pressing the cold-rolled steel plate into a shape of the bracket.

[6] In this case, an exposed portion of a base steel plate is formed on a complicated cut surface by press processing, and the plating layer is damaged, which causes a problem of a decrease in corrosion resistance of the entire bracket. This problem also affects durability of the vehicle.

[7] Accordingly, there is an acute need to develop a vehicle bracket with more improved corrosion resistance.

[8] As a background technology of the present disclosure, Korean Patent Application Laid-Open No. 10-2005-0089568 discloses a fixing bracket for assembling a vehicle fender panel.

[Disclosure]

[Technical Problem]

[9] An object of the present disclosure is to provide a vehicle bracket having a cut surface with improved corrosion resistance.

[10] Another object of the present disclosure is to provide a method of manufacturing a vehicle bracket, which is capable of improving corrosion resistance by forming an antirust coating layer, as a sealing film, on an entire cut surface and an entire outer surface of the vehicle bracket having the cut surface by press processing.

[11] The above-mentioned objects and other objects of the present disclosure all may be achieved by the present disclosure to be described below.

[Technical Solution]

[12] 1. One aspect of the present disclosure relates to a vehicle bracket.

[13] The vehicle bracket includes: a base steel plate; and a molten Zn-Al-Mg plating layer formed on the base steel plate, in which one or more cut surfaces are formed, in which an anti-rust coating layer is formed on the cut surface and the plating layer, and in which the anti-rust coating layer is formed by immersion in an anti-rust coating liquid including a metal coating liquid, which contains metal nitrate, and a surfactant at a mass ratio of 2 to 3 : 1.

[14] 2. In Specific Example 1, the molten Zn-Al-Mg plating layer may include 1.5 to 3.0 wt% of Zn, 1.5 to 2.5 wt% of Al, 1.5 to 2.5 wt% of Mg, and the remaining inevitable impurities.

[15] 3. In Specific Example 1 or 2, the metal coating liquid may include 3 to 5 wt% of aluminum nitrate, 5 to 10 wt% of silicon dioxide, and a residual amount of water.

[16] 4. In any one of Specific Examples 1 to 3, the surfactant may include 3 to 5 wt% of sodium sulfate, and a residual amount of water.

[17] 5 In any one of Specific Examples 1 to 4, no red rust may occur in a saltwater spray test with a saltwater concentration of 5%, a saltwater spray rate of 1.5 ml/h, and a continuous spray condition of 740 hours or more.

[18] 6. In any one of Specific Examples 1 to 5, no paint layer may be formed on the antirust coating layer.

[19] 7. Another aspect of the present disclosure relates to a method of manufacturing a vehicle bracket.

[20] The method of manufacturing a vehicle bracket includes: (a) preparing an alloy steel plate including a molten Zn-Al-Mg plating layer; (b) manufacturing a bracket shape by pressing the alloy steel plate; and (c) forming an anti-rust coating layer by immersing the bracket in an anti-rust coating liquid, in which the anti-rust coating liquid includes a metal coating liquid, which contains metal nitrate, and a surfactant at a mass ratio of 2 to 3 : 1.

[21] 8. In Specific Example 7, the metal coating liquid may include 3 to 5 wt% of aluminum nitrate, 5 to 10 wt% of silicon dioxide, and a residual amount of water.

[22] 9. In Specific Example 7 or 8, the surfactant may include 3 to 5 wt% of sodium sulfate, and a residual amount of water. [23] 10. In any one of Specific Examples 7 to 9, in step (c), the anti -rust coating liquid may be kept at 40 to 60°C.

[24] 11. In any one of Specific Examples 7 to 10, in step (c), the anti-rust coating liquid may be kept at pH 3.0 to 4.0.

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

[Advantageous Effects]

[26] According to the vehicle bracket according to the present disclosure, even in the case of the complicated structure having one or more cut surfaces, the anti -rust coating layer may be added to the upper portion of the cut surface, such that the entire plating layer is not corroded, which may remarkably reinforce corrosion resistance.

[27] According to the vehicle bracket of the present disclosure, a high corrosion-resistant Zn-Al-Mg ternary plated steel plate may be used to increase surface hardness, and the additional anti-rust coating layer may be formed on the cut surface, thereby significantly improving corrosion resistance.

[28] According to the method of manufacturing a vehicle bracket according to another aspect of the present disclosure, it is not necessary to form a separate plating layer and an additional paint layer. Further, the single process of forming the anti-rust coating layer on the outer surface of the Zn-Al-Mg ternary plated steel plate may increase corrosion resistance, thereby significantly improving efficiency of the process of manufacturing the vehicle bracket.

[Description of Drawings]

[29] FIG. l is a schematic view of a vehicle bracket according to a specific example of the present disclosure.

[30] FIG. 2 is a process flowchart of a method of manufacturing a vehicle bracket according to another aspect of the present disclosure.

[31] FIG. 3 illustrates scanning electron micrographs of the vehicle bracket having the antirust coating layer according to the specific example of the present disclosure and the vehicle bracket having no anti-rust coating layer.

[32] FIG. 4 illustrates photographs of the vehicle bracket according to the specific example of the present disclosure in accordance with a saltwater spray time.

[Mode for Disclosure]

[33] Hereinafter, the present disclosure will be described more specifically with reference to the accompanying drawings. However, the following drawings are provided just for more easily understanding the present disclosure, and the present disclosure is not limited to the flowing drawings. In addition, shapes, sizes, ratios, angles, numbers, and the like illustrated in the drawings are just exemplarily illustrated, and the present disclosure is not limited to the contents illustrated in the drawings.

[34] Throughout the specification, the same reference numerals denote the same constituent elements. In addition, in the description of the present disclosure, the specific descriptions of publicly known related technologies will be omitted when it is determined that the specific descriptions may unnecessarily obscure the subject matter of the present disclosure.

[35] The terms "comprise," "have," or "include" used in the present specification may mean that other constituent elements can be added unless these terms are used with the term "only". Unless otherwise particularly and clearly stated, the singular expressions used herein are intended to include the plural expressions.

[36] Unless otherwise separately and explicitly stated, analyses of constituent elements are interpreted as including error ranges.

[37] When a positional relationship between two components is described by using terms 'on,' 'above,' 'below,' 'at a lateral side of,' and the like, one or more components may also be positioned between the two components when term 'immediately,' or 'directly' is not used.

[38] The positional relationships such as 'upper,' 'upper surface,' 'lower,' and 'lower surface' are described based on the drawings but do not represent absolute positional relationships. That is, the positions of 'upper,' 'upper surface,' 'lower,' and 'lower surface' may be changed depending on observation positions.

[39] In the present specification, "a to b", which represents a numerical value range, is defined as ">a and <b".

[40] Hereinafter, a vehicle bracket according to a specific example of the present disclosure will be described in detail with reference to the drawings.

[41] FIG. l is a schematic view of a vehicle bracket according to a specific example of the present disclosure.

[42] With reference to FIG. 1, a vehicle bracket includes a base steel plate 100, plating layers 200, and anti-rust coating layers 300.

[43] The base steel plate 100 may include a steel plate capable of being plated with hot-dip galvanized layer. Particularly, the base steel plate 100 may be a cold-rolled steel plate.

[44] In case that the base steel plate 100 is a cold-rolled steel plate, the plating layer has a uniform thickness and a clean surface, such that a hot-dip galvanized layer plating layer may be easily formed.

[45] In case that the base steel plate 100 is a hot-rolled steel plate, an oxidation layer is formed by heat treatment, which makes it difficult to form a separate plating layer on an upper surface of the base steel plate 100. Further, because the oxidation layer itself has corrosion resistance, an additional plating process is not required. [46] The molten Zn-Al-Mg plating layer 200 may be formed by melting a metal element on the base steel plate 100.

[47] Specifically, a binary eutectic structure of Zn-MgZm and a ternary eutectic structure of Zn-Al-MgZn2 may be formed. In the process structure of Zn-MgZm, MgZm is more actively eluted to improve corrosion resistance of a cut surface, such that a large amount of the binary eutectic structure is preferably formed. In the specific example of the present disclosure, because the anti-rust coating layer is formed not only on an upper surface of a coating layer but also on the cut surface, it is not necessary to adjust Zn-Al-Mg composition in a plating bath to form a large amount of the binary eutectic structure.

[48] In the specific example, the molten Zn-Al-Mg plating layer 200 may include Zn: 1.5 to 3.0 wt%, Al: 1.5 to 2.5 wt%, and Mg: 1.5 to 2.5 wt%, and the remaining inevitable impurities.

[49] In the content range, the binary eutectic structure of Zn-MgZm and the ternary eutectic structure of Zn-Al-MgZm may be formed. In case that the plating layer is exposed to a corrosion environment, MgZm has lower corrosion electric potential than Zn, such that MgZn2 is eluted first in the corrosion environment. The eluted Mg forms Mg(OH)2 and reduces alkalinity in a cathode region, such that stable ZmfOHjxCb^O is formed, which may improve corrosion resistance.

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

[51] When the cut surface is formed, the molten Zn-Al-Mg plating layer 200 may be removed, such that corrosion resistance may deteriorate. However, because an antirust coating layer 300 is formed on the upper portion of the cut surface, corrosion resistance of the cut surface may be greatly improved. [52] In case that no anti-rust coating layer 300 is formed on the upper portion of the cut surface, corrosion such as white rust or red rust may occur in the corrosion environment.

[53] The anti-rust coating layer 300 is formed by immersion in an anti-rust coating liquid including a metal coating liquid, which contains metal nitrate, and a surfactant at a mass ratio of 2 to 3 : 1.

[54] The anti-rust coating layer 300 is formed by immersion in the anti-rust coating liquid including the metal coating liquid and the surfactant and then drying.

[55] In case that the anti-rust coating liquid includes the metal coating liquid, which contains metal nitrate, and the surfactant within the above-mentioned range, the dispersity of metal nitrate in the anti-rust coating liquid may increase, such that the anti-rust coating layer may be formed only by immersion. Further, a thickness of the anti-rust coating layer may be uniformized, and the metal coating liquid may be durably deposited on the plating layer.

[56] In the specific example, the metal coating liquid may include 3 to 5 wt% of aluminum nitrate, 5 to 10 wt% of silicon dioxide, and a residual amount of water.

[57] In case that the metal coating liquid includes aluminum nitrate within the above- mentioned range, a fine crystal structure may be formed, which may effectively increase not only corrosion resistance of the anti-rust coating layer but also hardness of the anti-rust coating layer.

[58] The silicon dioxide may effectively increase corrosion resistance of an alloy layer containing magnesium. Within the above-mentioned range, it is possible to increase not only corrosion resistance but also wear resistance, which may increase hardness of the anti-rust coating layer.

[59] In the specific example, the surfactant may include 3 to 5 wt% of sodium sulfate, and a residual amount of water.

[60] The sodium sulfate is an anionic surfactant. Within the above-mentioned range, the crystalline structure of aluminum nitrate may be stabilized, which may improve corrosion resistance.

[61] Red rust may not be formed on a vehicle bracket 1000 in a saltwater spray test with a saltwater concentration of 5%, a saltwater spray rate of 1.5 ml/h, and a continuous spray condition of 740 hours or more.

[62] The vehicle bracket 1000 has significantly increased corrosion resistance, such that red rust is not formed in a continuous saltwater spray test of 740 hours or more, for example, even though the saltwater is continuously sprayed at a saltwater concentration of 5% and a saltwater spray rate of 1.5 ml/h for 741 hours. Therefore, it is possible to significantly increase corrosion resistance.

[63] In the specific example, no paint layer may be formed on the upper portion of the antirust coating layer 300.

[64] No separate paint layer is formed on the plating layer of the vehicle bracket 1000, and the anti-rust coating layer 300 may be substituted for anti-rust paint.

[65] The anti-rust coating layer 300 is colored dark gray compared to the plating layer, which makes it possible to visually identify whether the anti-rust coating layer is formed.

[66] Another aspect of the present disclosure relates to a method of manufacturing a vehicle bracket.

[67] FIG. 2 is a process flowchart of a method of manufacturing a vehicle bracket according to another aspect of the present disclosure.

[68] With reference to FIG. 2, the method of manufacturing a vehicle bracket includes (a) preparing an alloy steel plate including a molten Zn-Al-Mg plating layer, (b) manufacturing a bracket shape by pressing the alloy steel plate, and (c) forming an anti-rust coating layer by immersing the bracket in the anti-rust coating liquid.

[69] First, a hot-dip galvanized steel plate is prepared (SI 00).

[70] The hot-dip galvanized steel plate may be an alloy steel plate made by forming a molten Zn-Al-Mg plating layer on an upper portion of a base steel plate.

[71] A bracket shape is manufactured by pressing the alloy steel plate (S200).

[72] The shape of the vehicle bracket may be determined by the pressing, and one or more cut surfaces may be formed.

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

[74] The method may include degreasing the vehicle bracket (S210).

[75] The degreasing removes oily substances remaining on the upper portion of the plating layer, such that the anti-rust coating layer may securely adhere.

[76] The method may include washing the vehicle bracket after the degreasing (S220).

[77] In the washing of the vehicle bracket, foreign substances on the surface may be removed in advance.

[78] The anti-rust coating layer is formed by immersing the bracket in the anti-rust coating liquid (S300).

[79] The anti-rust coating liquid may include the metal coating liquid, which contains metal nitrate, and the surfactant at a mass ratio of 2 to 3 : 1.

[80] The anti-rust coating liquid may be manufactured by mixing the metal coating liquid and the surfactant within the above-mentioned range, and the anti-rust coating layer may be formed by adjusting an immersion condition. The durability of the anti-rust coating layer may be improved by stabilizing the crystalline structure of the anti-rust coating layer. [81] In the specific example, the metal coating liquid may include 3 to 5 wt% of aluminum nitrate, 5 to 10 wt% of silicon dioxide, and a residual amount of water.

[82] The metal coating liquid contains aluminum nitrate, and the fine crystalline structure is formed on the anti-rust coating layer, which may increase corrosion resistance and also increase hardness of the anti-rust coating layer.

[83] In the specific example, the surfactant may include 3 to 5 wt% of sodium sulfate, and a residual amount of water.

[84] The surfactant may contain sodium sulfate and be used to manufacture the anti-rust coating liquid. The metal coating liquid may be dispersed to stabilize the crystalline structure.

[85] In S300, the anti-rust coating liquid may be kept at 40 to 60°C.

[86] For example, the temperature is preferably 50 to 60°C, and more preferably 50°C.

[87] Because the anti-rust coating liquid is maintained within the temperature range, the vehicle bracket may be uniformly coated by immersion.

[88] In S300, the anti-rust coating liquid may be kept at pH 3.0 to 4.0.

[89] Specifically, pH 3.6 to 4.0 is preferable, and pH 4.0 is more preferable.

[90] The anti-rust coating layer may be uniformly formed within the pH range, which may increase smoothness of the surface. In case that pH exceeds the above-mentioned range, precipitation may occur in the metal coating liquid.

[91] Within the pH range, the color of the anti-rust coating layer may be dark. For example, the anti-rust coating layer may have a dark gray color.

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

[93] In case that the immersion is performed within the time range, the thickness of the antirust coating layer may be uniformized, average illuminance may be decreased, such that the surface of the vehicle bracket may be smoothly formed. [94] After the immersion, the vehicle bracket is recovered and dried at room temperature, such that the vehicle bracket having the anti-rust coating layer may be manufactured.

[95] According to the vehicle bracket according to the present disclosure, the bracket shape having one or more cut surfaces is manufactured by pressing the base steel plate having the molten Zn-Al-Mg plating layer having high corrosion resistance, and then the antirust coating layer is formed again on the cut surface and the upper surface of the plating layer upper surface, such that corrosion resistance may be significantly improved, and hardness may also be increased.

[96] It is possible to ensure high corrosion resistance by simply immersing the vehicle bracket in the anti -rust coating liquid to form the anti -rust coating layer and then drying the vehicle bracket. Therefore, it is not necessary to perform a separate painting process for coping with a change in color of the vehicle bracket after coating, thereby significantly increasing manufacturing efficiency of the vehicle bracket.

[97] Hereinafter, examples are provided to assist in understanding the present disclosure. However, the following examples are only illustrative of the present disclosure, and the scope of the present disclosure is not limited to the following embodiment.

[98] Example 1. Manufacture of vehicle bracket

[99] A hot-dip galvanized steel plate (Zn: 1.5 wt%, Mg: 1.5 wt%, Al: 1.5 wt% alloy layer) was prepared, and a vehicle bracket shape was manufactured by cutting the hot-dip galvanized steel plate by a press machine.

[100] A vehicle bracket having a cut surface was degreased, washed twice, and then immersed in a bath containing an anti-rust coating liquid.

[101] A metal coating liquid containing 5 wt% of aluminum nitrate, 10 wt% of silicon dioxide, and 85 wt% of water was manufactured, and a surfactant containing 5 wt% of sodium sulfate and 95 wt% of water was manufactured. [102] The anti -rust coating liquid containing 25 wt% of the surfactant and 75 wt% of the metal coating liquid was prepared and inputted into a plating bath.

[103] Whether the anti-rust coating liquid is pH 4.0 was identified, a temperature of the antirust coating liquid was adjusted to 50°C, and then the vehicle bracket having the cut surface was immersed in the anti-rust coating liquid in the plating bath for 60 seconds.

[104] The vehicle bracket was recovered, washed twice, and dried at room temperature (25°C) for 24 hours or more, such that the vehicle bracket having the anti-rust coating layer was recovered.

[105] Experimental Example 1. Identification of anti-rust coating layer

[106] FIG. 3 illustrates scanning electron micrographs of the vehicle bracket having the antirust coating layer according to the specific example of the present disclosure and the vehicle bracket having no anti-rust coating layer.

[107] With reference to FIG. 3, the illuminance of the surface is increased and becomes non- uniform in case that no anti-rust coating layer is formed, as illustrated in FIG. 3A. However, as illustrated in FIG. 3B, in case that the anti-rust coating layer is formed again on the upper surface of the plating layer, it can be seen that the anti-rust coating layer durably adheres to the upper surface of the plating layer, such that the surface is smooth, and the crystalline structure of the anti-rust coating layer is stabilized.

[108] Experimental Example 2. Anti-rust coating liquid composition

[Table 1 ]

[109] Table 1 shows the identification of shapes of anti-rust coating layers in accordance with anti-rust coating liquid compositions.

[HO] With reference to Table 1 , it can be seen that in Example 1 , the smooth anti -rust coating layer having high smoothness is formed. However, in Comparative Example 1, almost no anti-rust coating layer is formed only by immersion in case that the metal coating liquid content is decreased compared to the examples. In Comparative Example 2, a thickness of an anti-rust coating layer is not uniform because of a large amount of metal coating liquid after immersion, and smoothness is low, which requires an additional painting process.

[111] Experimental Example 3. Saltwater spray test

[112] A saltwater spray test was performed to identify corrosion resistance of the vehicle bracket manufactured according to the embodiment.

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

[114] A saltwater tester (VT ST-200) was used to spray the saltwater, at an angle of 15 to 30°, to the vehicle bracket manufactured according to Example 1.

[115] FIG. 4 illustrates photographs of the vehicle bracket according to the specific example of the present disclosure in accordance with a saltwater spray time.

[116] According to the result of spraying saltwater for a total of 741 hours, white rust occurred on the vehicle bracket according to the embodiment after 429 hours had elapsed. However, it can be seen that red rust did not occur even after the saltwater was sprayed for 741 hours or more, such that very high corrosion resistance could be exhibited. In particular, it can be seen that red rust never occurred on the cut surface.

[117] Therefore, the anti-rust coating layer is formed on the vehicle bracket according to the present disclosure, and the high corrosion resistance and surface hardness are significantly increased, such that the vehicle bracket may be used as a WSS bracket for supporting an EPB cable used in an environment in which corrosion and vibration are present. In particular, the corrosion resistance of the cut surface may be increased, such that the corrosion resistance and hardness may be significantly improved on the WSS bracket having a complicated shape in comparison with the simple hot-dip galvanized steel plate.

[118] The embodiments of the present disclosure have been described above. It can be understood that those skilled in the art to which the present disclosure pertains can implement modifications without departing from the intrinsic characteristics of the present disclosure. Therefore, the disclosed embodiments need to be considered as being illustrative but not restrictive. The scope of the present disclosure is defined by claims rather than the above-mentioned description, and all the differences in the equivalent scope thereto should be construed as falling within the scope of the present disclosure.

[Description of Reference Numerals]

1000: Vehicle bracket

100: Base steel plate

200: Plating layer

300: Anti -rust coating layer