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(11) | EP 0 345 607 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Corrosion protection element for parts, particularly automotive parts, to be connected by screws, bolts, etc. |
| (57) The invention relates to a corrosion protection element (1) comprising a laminate
consisting of two spaced high-purity zinc foils (2), a layer of an elastic adhesive
sealing material (3) between said foils (2), and a coat of a permanently elastic adhesive
(4) on the side of one of said zinc foils facing away from the elastic adhesive sealing
material layer, said latter adhesive coat being covered by a strippable adhesive-protecting
liner (5). After the liner (5) has been withdrawn, the corrosion protection element
may be applied by placing it with its self-adhesive coating (4) down on the surface
of one of two parts in the area where they are to be connected. Because of its permanent
deformability, it will provide an optimum seal at the juncture between the parts as
they are being connected; at the same time, it provides long-term protection from
corrosion as the high-purity zinc foils (2) of the laminate provide cathodic anticorrosive
action. Relative movements of the connected parts will in no way impair the sealing
and anticorrosive effects the inventive corrosion protection elements affords. |
[0001] The invention relates to a corrosion protection element for parts, particularly automotive parts, to be connected by screws, bolts and the like and consisting at least in part of metal, said corrosion protective element being adapted to be provided between said parts at the juncture thereof and including zinc in layer form.
[0002] It is necessary frequently to provide for protection against corrosion between constructional components that are to be connected to each other -- such as, in the automotive industry, components that are to be attached to the chassis or to the body of a vehicle.
[0003] For obtaining optimum protection from corrosion, it has been known to provide a coat of zinc on the entire body of a vehicle. On all of the vehicle body surface, this coat of zinc will act as a cathode whenever corrosive processes take place. The provision of a coat of zinc on the entire surface of a vehicle body is most costly, however. In addition, problems arise when internally threaded bores must be provided on the body for attaching components; such internally threaded bores will disrupt the zinc coating. Even if such bores are provided on the body before the zinc coating is applied, movements of the attached components relative to the body at the threaded bores will again disrupt the zinc coating, giving rise to corrosive damage within a short period of time.
[0004] It has been known furthermore to use a self-adhesive zinc foil as an element affording protection from corrosion, such foil being provided at the juncture of rubber components and steel components or between other metal attachments, for example; see Japanese Patent 61,179,886. A zinc foil of this kind does not provide for a seal at the juncture of the parts to be connected and is damaged rather easily by mechanical movements of the parts between which it is located. As has been known, a satisfactory protection of connected parts from corrosion will be obtained by the application of several layers of paint; this again does not result in a seal between the parts to be connected. Besides, the coats of paint will be damaged by mechanical movements of the parts connected.
[0005] Optimum protection from corrosion is obtainable where the parts to be connected are high-grade steel, such as chrome-nickel steel. A suitable seal at the juncture between the parts to be connected may be obtained by any sealing compound or sealing tape which will accommodate slight mechnical movements. This kind of protection from corrosion is very expensive, however.
[0006] Finally, there has been known a great number of sealing compounds which are not impaired by relative movements of the parts to be connected. Compounds of this kind do not afford any protection from corrosion, however.
[0007] It is the object underlying the invention to provide in a cost-effective manner a corrosion protection element of the type specified above which provides an excellent seal at the juncture of the parts to be joined, as well as optimum protection from corrosion, regardless of relative movements of the parts connected to each other.
[0008] In accordance with the invention, this object is achieved by a laminate comprising two high-purity zinc foils providing cathodic anticorrosive action, said foils being disposed in a mutually overlying relationship and having therebetween a layer of an elastic sealing material, said laminate conforming in an optimum manner to and sealing the gap between the parts to be connected as these parts are being connected with each other.
[0010] It is preferred that the zinc foils be adhered to the layer of sealing material by means of adhesive layers.
[0011] The laminate may have any desired geometric shape in plan view. It is preferred that the laminate be manufactured in a continuous or strand form. The elastomer may be a paste composition on the basis of polyisobutylene, (butyl) or polyurethane, for instance, or may be present in the form of a closed-cell foam adhesive tape. The closed-cell form adhesive tape may be acrylic foam or a neoprene or polyether tape, for example. In the joining of the aforesaid parts such as the fixing of an attachment by means of screws, it is important that the elastic adhesive sealing material exhibit excellent conformability and strong adhesion for the desired sealing effect; in addition, it should be a closed-cell material.
[0012] For use of the inventive corrosion protective element in the automotive industry, it is of major importance that the laminate accept automotive body paints.
[0013] In a one-year long-term test of a test vehicle under corrosion promoting conditions corresponding to a vehicle life of about ten years in a normal environment, the inventive corrosion protection element was found not to be damaged or wear, and no corrosion was found in the areas where attachments were connected. As a result, the inventive corrosion protection element provides excellent protection from corrosion as well as an excellent seal particularly between screwed-on attachments and the substrate, such as fenders and the automobile body to which they are attached. The permanently elastic adhesive layer of the laminate provides for easy application of the inventive corrosion protection element in the vicinity of the bores provided in the attachments. As the screws are tightened, the laminate will in an optimum manner conform to and seal the gap between the parts to be joined, permanently sealing that gap. The zinc provides for cathodic anticorrosive action in the gap and on the bore walls. As the entire laminate is permanently elastic, it exhibits long life and stability against aging despite relative movements between the joined parts. Because of its advantages in the assembly process and the permanent anticorrosive effect, the inventive corrosion protection element is most cost-effective. The adhesive-protecting liner protects the permanently elastic self-adhesive layer from soiling before the laminate is put to use. The inventive corrosion protection element has major advantages particularly in the automotive, naval, and aircraft industries and for stationary installations which require permanent stability in a humid environment.
[0014] The inventive corrosion protection element will now be explained in greater detail under reference to the drawings.
Fig. 1 shows a schematic perspective view of the corrosion protection element;
Fig. 2 schematically shows the use of a corrosion protection element for fastening a fender to a wheel case by means of threaded bolts;
Fig 3 shows another embodiment of the invention, used to protect the fastening bolts of a bicycle stand.
[0015] As shown in Fig. 1, the corrosion protection element comprises a laminate 1 which may be manufactured in a continuous form and has two spaced high-purity zinc foils 2 having therebetween a layer 3 of an elastic adhesive sealing material engaging the facing sides of foils 2. A layer 4 of a permanently elastic adhesive is provided on the opposite side of lower zinc foil 2 (Fig. 1). In the storage condition of the corrosion protection element, that layer 4 is covered by an adhesive-protecting liner 5 which may be stripped away readily before use.
[0016] Fig. 2 shows the use of the corrosion protection element for fastening a fender 6 to the wheel case of a vehicle body 7. After bores 9 have been provided in the vehicle body and in fender 6 to be attached, adhesive-protecting line 5 is stripped from laminate 1, and the latter is applied with the self-adhesive surface of layer 4 of permanently elastic adhesive down on vehicle body 7 above bores 9 (in Fig. 2). Thereafter, fender 6 is fitted to the wheel case in vehicle body 7 and to the corrosion protection element placed thereon, and threaded bolts 10 are introduced in bores 9 and tightened to secure the fender to the wheelcase. As bolts 10 are tightened, laminate 1 of the corrosion protection element conforms in an optimum manner to and permanently seals the juncture 11 between fender 6 and wheel case 7. High-purity zinc foils 2 of lamnate 1 provide cathodic anticorrosive action in area 11 and in bores 9. Because of the permanent elasticity of the corrosion protection element, that element itself and the connection between the joined vehicle parts show a long life and a high stability against aging despite relative movements of fender 6 and the wheel case of vehicle body 7 during vehicle operation. In particular, the self-adhesive coating of laminate 1 and the deformability of layer 3 of an elastic adhesive sealing material provide for easy assembly of the corrosion protection element and for easy installation of fender 6 on wheel case 7 of the vehicle body.
[0017] Fig 3 shows another example of the use of the inventive element on a roofed bicycle stand, which comprises supporting structure of steel beams 13 which is maintained in the assembled condition by means of threaded bolt-and-nut fastener combinations 14 provided adjacent sheet-metal roof sections 15. For protection from corrosion, the inventive laminate 1 is provided above and below fastener combinations 14 to seal joint 16. In conventional assemblies of this kind, corrosion will be caused by the slight but unavoidable relative movements of the connected parts that are caused by wind and other mechanical forces acting on the stand.
Example
[0018] A multi-layer construction consisting of the following materials including dimensional data:
| Material | Description | Dimensions |
| Zinc Foil | Matt Silver 99.5 purity | .075 mm thickness |
| Sealant | Grey paste of Polybuten type | 1.645 mm thickness |
| Zinc Foil | Matt Silver 99.5 purity | .075 mm thickness |
| Adhesive | Modified acrylate | .125 mm thickness |
| Liner | Siliconized protection paper | .080 mm thickness |
| Total thickness | 2.000 mm | |
| Width | 8.000 mm | |
| Total length | 1.0 m | |
| Initial adhesion (AFER A-steel, 180° peel 300 mm/min) | > 20 N/25 mm | |
| Weight/area (without liner) | 0.50 +/- 0.05 grs/cm² |
1. Corrosion protection element for components to be fastened by means of screws,
bolts and the like and consisting at least partly of metal, and particularly for automotive
parts to be connected, said element being adapted to be provided between such parts
at the point of connection thereof and including zinc in layer form, characterized, in that the element comprises a laminate (1) of two high-purity zinc foils (2) providing
cathodic anticorrosive action, said foils being disposed in a mutually overlying relationship
and having therebetween a layer (3) of an elastic sealing material, and in that laminate
(1) conforms to and seals in an optimum manner the area of connection (11) as the
two members (6, 7) are firmly fastened to each other.
2. Corrosion protection element as in claim 1, characterized in that laminate (1) has a permanently elastic adhesive layer (4) provided on a surface
of one of high-purity zinc foils (2) which faces away from layer (3).
3. Corrosion protection element as in claim 1 and 2, characterized in that the storage condition of laminate (1) adhesive layer (4) is covered by an
adhesive-protecting liner (5) and in that laminate (1) is adapted to be applied for
self-adhesion in the area of fasteners (10, 14) by means of adhesive layer (4) to
one of the members to be connected, such application being subsequent to the removal
of liner (5).
4. Corrosion protection element as in any one of claims 1 to 3, characterized in that the sealing material of the layer (3) is tacky.
5. Corrosion protection element as in any one of claims 1 to 4, characterized in that in plan view laminate (1) has any desired geometric shape.
6. Corrosion protection element as in any of claims 1 to 4, characterized by laminate (1) being adapted to be manufactured in a continuous form.
7. Corrosion protection element as in any one of claims 1 to 6, characterized in that elastic adhesive sealing material (3) is a composition in paste form.
8. Corrosion protection element as in any one of claims 1 to 6, characterized by layer (3) of said elastic adhesive sealing material being formed of a closed-cell
foam adhesive tape.
9. Corrosion protection element as in claim 8, characterized in that closed-cell foam adhesive tape (3) consists of acrylic foam.
10. Corrosion protection element as in claim 8, characterized in that closed-cell foam adhesive tape (3) is neoprene tape.
11. Corrosion protection element as in claim 8, characterized in that closed-cell foam adhesive tape (3) is a polyether tape.
12. Corrosion protection element as in any one of the preceding claims, characterized in that laminate (1) accepts body paint.