EP0345607B1

EP0345607B1 - Corrosion protection element for parts, particularly automotive parts, to be connected by screws, bolts, etc.

Info

Publication number: EP0345607B1
Application number: EP89109739A
Authority: EP
Inventors: Ralf A. Scharpenack
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1988-06-08
Filing date: 1989-05-30
Publication date: 1992-09-09
Anticipated expiration: 2009-05-30
Also published as: CA1339407C; KR910001267A; DE3819495C1; EP0345607A1; JPH0277371A

Description

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.
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.
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.
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 JP-A-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.
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.
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.
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.
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.
Preferred embodiments of the invention are defined by dependent claims 2 to 12.
It is preferred that the zinc foils be adhered to the layer of sealing material by means of adhesive layers.
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.
For use of the inventive corrosion protective element in the automotive industry, it is of major importance that the laminate accept automotive body paints.
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.
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.

As shown in Fig. 1, the corrosion protection element comprises a laminate 1 which may be manufactured in a strand 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.
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 laminate 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.
Fig 3 shows another example of the use of the 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 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

A multi-layer construction consisting of the following materials including dimensional data:

Claims

Corrosion protection element for parts to be connected by means of screws, solts and the like and consisting at least partly of metal, said element 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.
Corrosion protection element according to claim 1, characterized in that the laminate (1) has a permanently elastic adhesive layer (4) provided on a surface of one of the high-purity zinc foils (2) which faces away from layer (3).
Corrosion protection element according to claims 1 and 2, characterized in that in the storage condition, the adhesive layer (4) of laminate (1) is covered by an adhesive-proctecting liner (5) and in that said laminate (1) is adapted to be applied for self-adhesion in the area of fasteners (10, 14) by means of the adhesive layer (4) to one of the members to be connected, such application being subsequent to the removal of liner (5).
Corrosion protection element according to any one of claims 1 to 3, characterized in that the sealing material of the layer (3) is tacky.
Corrosion protection element according to any one of claims 1 to 4, characterized in that the laminate (1) is adapted to be manufactured in a strand form.
Corrosion protection element according to any one of claims 1 to 5, characterized in that the elastic adhesive sealing material (3) is a composition in paste form.
Corrosion protection element according to any one of claims 1 to 5, characterized in that the layer (3) of said elastic adhesive sealing material is formed of a closed-cell foam adhesive tape.
Corrosion protection element according to claim 7, characterized in that the closed-cell foam adhesive tape (3) consists of acrylic foam.
Corrosion protection element according to claim 7, characterized in that the closed-cell foam adhesive tape (3) is a neoprene tape.
Corrosion protection element according to claim 7, characterized in that the closed-cell foam adhesive tape (3) is a polyether tape.
Corrosion protection element according to any one of the preceding claims, characterized in that the laminate (1) accepts body paint.