JP2019214779A - Anti-corrosion structure and formation method thereof - Google Patents

Abstract

To provide an anti-corrosion structure capable of preventing corrosion of an overlapping part of metal members having difficulty in forming a paint film, and especially applicable preferably to an automobile; and to provide a formation method thereof.SOLUTION: An anti-corrosion structure of a junction 8 for bonding two metal members 7A, 7B at least either of which comprises a Zn-plated steel sheet, includes sealers 19, 21 sealing the outer periphery of the junction 8, and having at least an expanded-and-formed part, and a protective layer 22 comprising basic zinc chloride formed on a Zn-plating layer 16 positioned inside the junction 8.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an anticorrosion structure that can be suitably applied to an automobile body and a method of forming the same.

  2. Description of the Related Art A typical automobile body is formed of a plurality of panels such as a steel plate and an aluminum material formed by press molding, casting, or the like. Most of these panels are generally assembled by overlapping the ends of adjacent panels and joining them by spot welding, riveting, caulking, or the like. This is because point joining is superior in productivity to line joining.

  After such a joining step, an undercoating step is generally performed to ensure corrosion resistance. Furthermore, in the lower part of the vehicle body, water and mud on the road surface wound up by the tire adhere to the surface during running, and the undercoating film is easily damaged (chipping) by stones or the like.

For this reason, many types of steel sheets are used for panels that have been subjected to various types of Zn-based plating (hot-dip Zn plating, electric Zn plating, etc.) in advance to improve corrosion resistance.
Here, Zn is a metal which is apt to corrode, and causes slight corrosion at an early stage even in a mildly corrosive environment. However, in the case of Zn-based plating, basic zinc chloride [ZnCl ₂ .4Zn (OH) ₂ ] generated as a corrosion product covers the plating and the surface of the steel sheet, and becomes a protective layer. Thereby, the effect of suppressing the progress of plating and corrosion of the steel sheet can be obtained. This basic zinc chloride is a non-conductor. For this reason, at the joint (joining surface) between the steel plate and the aluminum material, a large electric resistance is obtained with respect to the galvanic corrosion current flowing between the two plates, and there is also an effect of suppressing galvanic corrosion. However, the anticorrosion effect of the Zn-based plating is not sufficient, so that the anticorrosion effect of the Zn-based plating and the undercoating are combined. As a result, even when the vehicle is used under severe conditions for a long period of time, it is possible to maintain the functions and appearance of the general surface (other than the gap and the bag-shaped portion) of the vehicle body.

  However, in an automobile body, since the undercoat is applied after the panel joining process, the undercoat is difficult to enter into a narrow gap inside the joining surface of the joining, and it is difficult to form a paint film. Furthermore, when moisture enters the gap between the narrow mating surfaces from the opening of the mating surface, the corrosion progresses more rapidly than that of the general surface due to the occurrence of crevice corrosion and the like, and defects such as perforation occur early. appear. Furthermore, in the joining of a steel sheet and an aluminum material, galvanic corrosion occurs, and more rapid corrosion occurs in the aluminum material. As a countermeasure, a waterproof sealer is generally applied to the opening of the mating surface after the undercoating to prevent the intrusion of moisture into the mating surface by blocking the sealer from the outside.

  In some cases, the waterproof sealer is applied only to the opening on one side that is exposed to water during driving, etc., but water from the tires or rainwater is applied from both sides of the joint (tire side / engine room side). In the receiving member, a waterproof sealer is applied to both ends of the joint surface of each panel to prevent water from penetrating into the joint surfaces. However, if a part of the waterproof sealer is cracked or peeled off due to long-term use of the automobile, moisture penetrates into the mating surfaces due to a capillary phenomenon even in a minute gap. At this time, since the inside of the mating surface is a bag-shaped portion and a narrow space where there is no ventilation with the outside, crevice corrosion occurs. When the crevice corrosion phenomenon occurs, the mating surfaces are acidified, and the acidification makes it difficult for basic zinc chloride to serve as a protective layer to be generated. For this reason, corrosion, especially crevice corrosion occurs, while the anticorrosion effect does not function, and the corrosion of the Zn-based plating and the steel sheet proceeds. In joining a steel sheet and an aluminum material, a problem occurs in that the corrosion of the aluminum material progresses rapidly due to the galvanic corrosion phenomenon.

  As a conventional technique for solving these problems, there is a method using high corrosion resistance plating disclosed in Patent Document 1. However, in order to improve the corrosion resistance of the joint surface, which is a small area, the entire panel is subjected to an expensive surface treatment as compared with general Zn-based plating. It is not efficient. Further, in the high corrosion resistance plating, as in the case of the Zn-based plating, the formation of a protective layer such as basic zinc chloride does not easily occur in the mating surfaces, so that the original corrosion resistance of the plating is hardly exhibited.

JP 2001-11665A

  The present invention provides an anticorrosion structure and a method for forming the anticorrosion structure, which can prevent corrosion of a superposed portion of a metal member on which a coating film is difficult to be formed, and can be suitably applied particularly to automobiles. The purpose is to:

  In order to achieve the above object, the anticorrosion structure according to the present invention is a corrosion prevention structure of a joint for joining two metal members, at least one of which is made of a Zn-based plated steel sheet, and an outer periphery of the joint is formed. A sealer that is sealed and at least partially expanded is formed, and a protective layer made of basic zinc chloride is formed on a Zn-based plating layer located inside the joint.

  In one embodiment of the anticorrosion structure according to the present invention, the two metal members constitute a closed cross-sectional space, the closed cross-sectional space has a through hole for painting the inner surface thereof, and the sealer The joint in the closed section space is sealed.

  In one embodiment of the anticorrosion structure according to the present invention, both of the two metal members are made of a Zn-based plated steel sheet.

  In one embodiment of the anticorrosion structure according to the present invention, one of the two metal members is made of a Zn-based plated steel sheet, and the other is made of an aluminum material.

  The present invention, in another aspect, is a method for forming an anticorrosion structure, at least one of which is made of a Zn-based plated steel sheet, a method for forming an anticorrosion structure at a joint for joining two metal members, A protective layer made of basic zinc chloride is formed on the Zn-based plating layer located inside the joint, and then at least a part of a sealer for sealing the outer periphery of the joint is expanded to form the joint. To complete the sealing of the part

  ADVANTAGE OF THE INVENTION According to this invention, the corrosion prevention structure which can prevent the corrosion of the overlap part of the metal member in which a coating film is hard to be formed, and can be suitably applied especially to an automobile, and its formation method are provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual perspective view explaining one Embodiment of the motor vehicle to which the anticorrosion structure and its formation method which concern on this invention are applied. 1 is a conceptual cross-sectional view illustrating a general cross-sectional structure of a panel to which an anticorrosion structure and a method for forming the anticorrosion structure according to the present invention are applied. It is a flowchart explaining one Embodiment of the formation method of the anticorrosion structure which concerns on this invention. It is sectional drawing which shows the joint part of panels for explaining the procedure about one Embodiment of the formation method of the anticorrosion structure which concerns on this invention. It is sectional drawing which shows the joint part of panels for explaining the procedure about one Embodiment of the formation method of the anticorrosion structure which concerns on this invention. It is sectional drawing which shows the joint part of panels for explaining the procedure about one Embodiment of the formation method of the anticorrosion structure which concerns on this invention. It is a flowchart explaining other embodiment about the formation method of the anticorrosion structure which concerns on this invention. It is sectional drawing by the VIII-VIII line of FIG. 1 which shows the joint part of panels for explaining the procedure of other Embodiment about the formation method of the anticorrosion structure which concerns on this invention. It is sectional drawing by the VIII-VIII line of FIG. 1 which shows the joint part of panels for explaining the procedure of other Embodiment about the formation method of the anticorrosion structure which concerns on this invention. It is sectional drawing by the VIII-VIII line of FIG. 1 which shows the joint part of panels for explaining the procedure of other Embodiment about the formation method of the anticorrosion structure which concerns on this invention.

  Hereinafter, embodiments of a corrosion prevention structure and a method for forming the same according to the present invention will be described with reference to the accompanying drawings. The following embodiment is an example for understanding the present invention. The present invention is not limited by the following embodiments.

FIG. 1 conceptually shows an embodiment of an automobile body to which the anticorrosion structure and the method for forming the anticorrosion structure according to the present invention are applied. FIG. 1 is illustrated very conceptually. A vehicle body 1 includes a roof panel 2, a dash panel 3, a pillar 4, a side sill 5, and a side member 6. What is shown in a panel shape is a panel 7 for a front tire house. The panel 7 is manufactured by joining at least two panels.
Note that the panel 7 is an embodiment of a metal member to which the present invention is applied.

FIG. 2 conceptually shows a cross section of the joint 8 of the panel 7. The panel 7 is formed by joining the panel 7A and the panel 7B to each other at the mating surface 9 as shown in FIG. FIG. 2 shows a state before the joining is completed. The left side from the panel 7A is the tire side, and the right side from the panel 7B is the engine room side. The panel 7A and the panel 7B are joined together at respective mating surfaces 9, 9. Such a panel 7 is wet 11 and 12 from both the tire side and the engine room side.
FIG. 2 illustrates the panel 7A and the panel 7B in a vertical (vertical) direction. However, in the description that follows using this specification and the drawings, the panel may be shown in a horizontal direction and may be shown as a mirror image of FIG. Even in such a case, there is no difference in the technical concept of the present invention.

FIG. 3 shows a general method for manufacturing the panel 7.
First, panel components such as the panels 7A and 7B are formed by pressing or casting (step 301).
Next, these panels 7A and 7B are joined (step 302). Then, an undercoat is applied (step 303). Thereafter, a sealer is applied (Step 304). In step 304, wax application is performed as needed. Finally, a middle / overcoating step 305 is performed. The coating step is generally performed as an electrodeposition coating step.

  Next, an embodiment of the anticorrosion structure and the method for forming the same according to the present invention will be described with reference to FIGS.

FIG. 4 shows a state before the sealing of the joint 8 is completed in the sealer application step 304 of FIG. In the embodiment shown in FIGS. 4 to 6, the panels 7A and 7B use a steel plate plated with Zn.
The method for forming the anticorrosion structure according to the present embodiment will be described with reference to FIGS. 4 to 6, so that the anticorrosion structure itself according to the present embodiment will also be described.

As described with reference to FIG. 2, the panel 7A and the panel 7B are point-joined at the mating surfaces 9, 9 (joining step 302 in FIG. 3). A gap 13 is formed between the mating surfaces 9. The panels 7A and 7B adopt a steel plate 15 on which a Zn-based plating 16 is applied.
After the point bonding, the undercoat is applied to both sides of the panels 7A and 7B to form the undercoat film 17 (undercoat step 303 in FIG. 3).

After the completion of the undercoating step 303, a waterproof sealer 19 is applied to one of the openings 18 of the gap 13 as in the related art to shut off the outside (step 304 in FIG. 3). In the same step 304, the foamable resin 21 is applied to the other opening 20 at a predetermined position in the vicinity thereof. FIG. 4 shows a cross-sectional structure, in which the waterproof sealer 19 and the foamable resin 21 extend in a direction perpendicular or substantially perpendicular to the paper surface.
Here, ventilation can be secured between the inside of the gap 13 and the outside through the opening 20.

  As a material constituting the foamable resin 21, a commercially available material known to those skilled in the art is used. Preferably, a foamable resin that becomes a hard foamed polyurethane after foaming and curing is used. Such a foamable resin generally includes a catalyst (an amine compound or the like), a polyisocyanate having two or more NCO (isocyanate) groups and a polyol having two or more OH (hydroxyl) groups, a blowing agent (water, Fluorocarbon), a foam stabilizer (silicone oil) and the like. After being applied to the panel, a foaming reaction and a resinizing reaction occur simultaneously, and after curing, a uniform plastic foam is formed. It should be noted that other resins can be used as long as they are foamable resins exhibiting such behavior.

Here, the foamable resin 21 is a foamable resin whose volume expansion due to foaming is gently continued for 5 to 30 days, and which can maintain waterproofness and airtightness even after the completion of volume expansion, and is hardly connected with pores due to foaming. use.
Note that the foamable resin 21 is grasped as forming a part of the sealer after the completion of the volume expansion.

Due to this attribute, the foamable resin 21 starts to expand in volume as shown in FIG. 5 after being applied near the opening 20. On the other hand, the Zn-based plating (layer) 16 exposed on the mating surfaces 9 and 9 even after the undercoating reacts due to the presence of water vapor in the air, and starts forming the protective layer 22 (FIG. 5). That is, during the sealer coating process 304, since the inside of the gap 13 is kept ventilated to the outside, slight corrosion occurs on the surface of the Zn-based plating 16 due to intrusion of moisture (moisture or the like), and the anticorrosion effect is high. protective layer 22 [basic zinc chloride _{{ZnCl 2 · 4Zn (OH)} 2}] occurs. After 5 days or more, the basic zinc chloride will be in a sufficient amount, and the completed protective layer 22 will be obtained. Note that, in the present embodiment, the operation until the protective layer 22 is formed is included in the sealer application step 304.

  When the formation of the protective layer 22 is completed as shown in FIG. 6, the volume expansion of the foamable resin 21 is also completed, and the opening 20 is also closed. A known commercially available resin can be appropriately selected as the foamable resin 21 to be used in accordance with such timing.

  Thereafter, a middle / overcoating step 305 (FIG. 3) is performed as required in the specifications.

  When the volume expansion of the foamable resin 21 is completed, the sealing of the outer periphery of the joint 8 is completed. That is, the method for forming the anticorrosion structure according to the present embodiment is completed, and the anticorrosion structure according to the present embodiment is completed.

  In the anticorrosion structure according to the present embodiment, the inside of gap 13 and the outside are shut off, and no ingress of moisture occurs. As described above, by preventing the penetration of moisture into the gap 13, the progress of corrosion in the gap 13 can be stopped for a long period of time.

  Further, in the anticorrosion structure according to the present embodiment, cracks and peeling 23 due to aging deterioration occur in the waterproof sealer 19 and / or the foamable resin 21 due to long-term use under severe conditions, and the water 24 Even when it penetrates into the inside, the progress of corrosion can be largely suppressed by the protective layer 22.

  According to the above-mentioned effects, even without using expensive high-corrosion-resistant plating or high-corrosion-resistant steel sheet, a sufficient anticorrosion effect can be obtained with a Zn-based plated steel sheet generally used in automobiles. Also, there is no need to apply a rust preventive to the mating surfaces. As a result, the formation of the protective layer on the mating surfaces is not hindered by the low-viscosity rust preventive agent, and the high-viscosity rust preventive agent does not cause insufficient short-press welding.

  In the anticorrosion structure according to the present invention, the combination of the panels 7A and 7B may be a combination of a steel plate and an aluminum material. In this case, even if water enters between the steel sheet and the aluminum material, the protective layer of the basic zinc chloride, which is a non-conductor, has a large electric resistance, and the galvanic corrosion current between the steel sheet and the aluminum material is significantly reduced. Corrosion can be greatly reduced. In addition, in the combination of a steel sheet and an aluminum material, a Zn-based plated steel sheet is used for a steel sheet panel. As the aluminum material, any of those having a surface treatment such as Zn-based plating and those having no surface treatment can be employed.

  As described above, in the present embodiment, the foamable resin 21 is applied after the undercoating process 303 as in the case of the waterproof sealer 19. However, it may be applied after the panel forming step 301 or the joining step 302. However, before the expansion of the foamable resin 21 and the corrosion of the mating surfaces 9 and 9 do not progress, the process up to the undercoating step 303 is immediately performed. In addition to the application of the liquid / gel foamable resin 21, a sheet-like material may be provided by adhesion, adhesion, baking, or the like.

  4 to 6 are conceptual sectional views, and should be read in accordance with the gist of the present invention.

[Modification 1]
Another embodiment of the anticorrosion structure and the method for forming the same according to the present invention will be described with reference to FIGS.

  The body frame parts such as the pillars 4, the side sills 5, and the side members 6 shown in FIG. 1 are generally formed by joining a plurality of panels together in a monaka manner, and are frame-shaped members having a closed sectional space. ing. In particular, the side sill 5 and the side member 6 are members located at the lower part of the vehicle body and exposed to a severe corrosive environment. In addition, since these members are provided with a plurality of holes (through holes) for undercoating and draining the inside, it is difficult to prevent moisture from entering the inside.

  In the first modification, as shown in FIG. 7, a foamable resin setting step 301B is performed after the panel forming step 301. In the foamable resin setting step 301B, the foamable resin 21 is set on the panel 7C.

In this manner, as shown in FIG. 8, the panels 7C and 7D are joined together in the joining step 302 in a monaka manner. Panels 7C and 7D are made of the same steel plate as panels 7A and 7C in FIG.
In FIG. 7, steps denoted by the same reference numerals as those in FIG. 3 are steps having the same contents as those described with reference to FIG. In addition, in FIGS. 8 to 10, the components described in FIGS. 4 to 6 with the same reference numerals as those in FIGS. 4 to 6 are applied in accordance with the understanding of those skilled in the art.

  As shown in FIG. 9, after the foamable resin 21 is applied to the vicinity of the opening 20, volume expansion starts as described with reference to FIG. 5. On the other hand, the Zn-based plating (layer) exposed on the mating surfaces 9 and 9 reacts due to the presence of water vapor in the air, and starts forming the protective layer 22. This is also the same as that already described with reference to FIG. The paint to be applied in the undercoating step 303 (FIG. 7) is introduced through the undercoating holes 25 which are through holes. Thereby, the inner surface of the closed section space 26 can be painted.

  When the formation of the protective layer 22 is completed as shown in FIG. 10, the volume expansion of the foamable resin 21 is also completed, and the opening 20 is also closed.

  After that, a middle / overcoating process is performed as required in the specifications.

  Also in the first modification, the same effects as those of the embodiment described with reference to FIGS. 4 to 6 can be expected. That is, an effect of closing the opening 20 by the foamable resin 21 and an effect of preventing the mating surface 9 from being corroded by the protective layer 22 can be expected. In addition, since the foamable resin 21 expands and is present in the closed cross section space 26, an anti-vibration effect can be expected.

[Modification 2]
In the anticorrosion structure according to the present invention, in still another embodiment, a waterproof sealer 19 (FIG. 6) is applied to a severely corrosive environment side, and a foamable resin 21 (FIG. 6) is applied to a gentle side. For example, in a front tire house, a waterproof sealer is applied on the tire side, and a foaming resin is applied on the engine room side.
Accordingly, on the side where the corrosive environment is severe, the infiltration of moisture into the mating surface can be prevented for a long time by a waterproof sealer having a waterproof effect and a higher durability than the foaming resin. Until the volume expansion of the foamable resin is completed, excessive Zn-based plating corrosion can be prevented by infiltrating water (moisture or the like) into the mating surfaces from a mild side of the corrosive environment.

REFERENCE SIGNS LIST 1 vehicle body 2 roof panel 3 dash panel 4 pillar 5 side sill 6 side member 7, 7A, 7B, 7C, 7D panel 8 joining portion 9 mating surface 10 point joining 11, 12 wet 13 gap 15 steel plate 16 Zn-based plating 17 paint coating 18 Opening 19 Waterproof Sealer 20 Opening 21 Foamable Resin 22 Protective Layer 25 Undercoating Hole 26 Closed Section Space 301 Panel Forming Step 301B Foaming Resin Installation Step 302 Joining Step 303 Undercoating Step 304 Sealer Applying Step 305 Top coating process

Claims (5)

At least one of which is made of a Zn-based plated steel sheet, is a corrosion-resistant structure of a joint for joining two metal members,
Sealing the outer periphery of the joining portion, at least a part of the sealer is formed to expand,
A protective layer made of basic zinc chloride formed on the Zn-based plating layer located inside the bonding portion.   The two metal members constitute a closed cross section space, the closed cross section space has a through hole for painting the inner surface thereof, and the joint in the closed cross section space is sealed by the sealer. The anticorrosion structure according to claim 1, wherein:   The anticorrosion structure according to claim 1, wherein both of the two metal members are made of a Zn-based plated steel sheet.   The anticorrosion structure according to claim 1, wherein one of the two metal members is made of a Zn-based plated steel sheet and the other is made of an aluminum material. At least one is made of a Zn-based plated steel sheet, a method for forming a corrosion-resistant structure of a joint for joining two metal members,
After forming a protective layer made of basic zinc chloride on the Zn-based plating layer located inside the bonding portion,
A method for forming an anticorrosion structure, wherein the sealing of the joint is completed by expanding at least a part of a sealer for sealing the outer periphery of the joint.

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