GB2171333A

GB2171333A - Method and apparatus for preparing the surface of a component for bonding to another component

Info

Publication number: GB2171333A
Application number: GB08504696A
Authority: GB
Inventors: Patrick George Selwood; Anthony Maddison
Original assignee: BL Technology Ltd
Current assignee: BL Technology Ltd
Priority date: 1985-02-23
Filing date: 1985-02-23
Publication date: 1986-08-28
Also published as: GB8504696D0

Abstract

A method a preparing the surface of a component, eg a body panel of a motor vehicle, in which a pre-treatment solution is applied onto localised areas of the surface by first application means, eg a spray nozzle, moving across the surface, and an adhesive is applied onto the pre-treated areas by second application means moving across the surface, preferably less than 60 seconds after completion of the pre-treatment. Components prepared in this matter can then be bonded or weld-bonded together.

Description

SPECIFICATION Method and apparatus for preparing the surface of a component for bonding to another component This invention relates to a method and apparatus for preparing the surface of a component for bonding to another component.

The durability of adhesive bonds to most substrates is greatly dependent on surface preparation of the substrate. The substrate may be pre-treated by mechanical, chemical or electro-chemical means. In general, the pre-treatment is carrier out either continuously whilst the substrate is still in strip form or in a batch process after the strip has been cut into discrete lengths and/or formed into components of desired shapes. Such batch processes usually involve dipping the components into baths of appropriate materials. This can be wasteful of the materials used, is time consuming, and is inconvenient when adhesive needs to be applied onto the pre-treated surface within a given time limit to avoid deterioration of the pre-treated surface.

According to a first aspect of the present invention there is provided a method of preparing the surface of a component for bonding to another component comprising the steps of: applying a pre-treatment solution onto localised areas of the surface from first application means moving across the surface; allowing the pre-treatment solution time to treat the surface and to dry; and applying adhesive on the pre-treated areas of the surface from second application means moving across the surface.

According to a second aspect of the present invention there is provided apparatus for preparing the surface of a component for bonding to another component in accordance with the method of claim 1 comprising drive means for moving a plurality of application means across the surface of the component, first application means being arranged to apply a pre-treatment solution onto localised areas of the surface and second application means being arranged to apply adhesive onto the pre-treated areas of the surface.

Preferred features of the invention will be apparent from the subordinant claims of the specification.

Preferred embodiments of methods and apparatus according to the present invention will now be described merely by way of example.

The invention is particularly applicable to the pre-treatment of components formed from aluminium sheet and which are to be bonded or weld bonded together, for example the body panels of a motor vehicle. It is desirable to pre-treat the surface of aluminium sheet prior to application of the adhesive in order to produce strong and durable bonds. The pre-treatment may, for instance, comprise the application of a solution containing phosphate, hexavalent chromium and fluoride such as the solution known as Bonderite 705 (Trademark) produced by Pyrene Chemical Services Limited or Alodine 407/47 (Trademark) produced by ICI plc.

Such solutions produce a conversion coating on the aluminium sheet which comprises at least 5% by weight of chromium and preferably at least 20%. Alternatively, a "no-rinse" pre-treatment may be used such a pre-treatment using an aqueous solution comprising partially reduced chromic acid and finely divided silica. An example of this type of pre-treatment is described in US Patent Specification No. 3706603 and may employ a solution known as Accomet C (Trademark) produced by Albright and Wilson Limited. Such a solution also produces a surface layer containing at least 5% by weight of chromium and preferably at least 20%.

The pre-treatment solution is applied by first application means such as a spray nozzle to localised areas of components which are to be joined together. The first spray nozzle is moved across the surface of the component for example by a robot arm and applies the pre-treatment solution in a series of localised areas, eg at intervals around the periphery of the components. If appropriate, the surface of the component should be degreased and cleansed prior to application of the pre-treatment solution, this being effected by means of a further spray nozzle which applies an appropriate cleaning solution to the areas of the components which are to be pre-treated. The pre-treatment itself may require the application of two or more solutions and these may be applied by a series of spray nozzles moving across the surface in succession.

After the aluminium has been pre-treated and dried, adhesive is applied onto the pre-treated areas of the component by a second spray nozzle which may also be moved across the surface by a robot arm.

The adhesive is applied shortly after the application of the pre-treatment solution and preferably within 60 seconds of the completion of the pretreatment process. If necessary, the pre-treated areas may be dried by warm air before the adhesive is applied. The adhesive may be in liquid, paste, film or powdered form. The adhesive is preferably an epoxide adhesive such as that produced by the 3M Company under the Trademark EC2214 or that produced by Permabond Inc under the Trademark ESP105. However, acrylic and phenolic adhesives can also be used.

The invention may also be applied to the pretreatment of steel sheet. In this case the surface of the steel may first be degreased by application of an alkaline solution from a first spray nozzle to produce a hydrophilic surface. A pretreatment solution such as Accomet C (Trademark) mentioned above is then applied by a second spray nozzle. Alternatively, a modified pretreatment solution, which can be applied to a hydrophobic surface, may be applied without the need for the degreasing step.

As mentioned above, the robot arms carrying the spray nozzles may be arranged to move the spray nozzles over the surface of the components being prepared. Alternatively, the components themselves may be moved relative to the spray nozzles.

Following the pre-treatment and subsequent ap plication of adhesive, the components may be joined together. Preferably, the components are spot-welded or rivetted together to hold the components in place whilst the adhesive cures and to increase the strength of the bond formed particularly the peel strength of the bond.

The various solutions and materials mentioned above can be applied by means other than the spray nozzles described, for instance by rollers or by mechanical brushes.

The method described above is particularly suitable for preparing the surface of a component which cannot conveniently be prepared before it is assembled into a structure, for instance when a roof panel is to be bonded to a conventionally spot-welded motor vehicle body to avoid unsightly spot-welds on the roof of the vehicle. It would be impractical to pre-treat the entire windscreen aperture panel, vehicle side panels and the tailgate aperture panel to which the roof panel is to be attached. The method is also suitable for low volume applications. As the adhesive is applied shortly after completion of the pre-treatment process, any risk of contaminating the pre-treatment areas is virtually eliminated. This method is thus suitable for use with pre-treatments which have poor storage characteristics. The pre-treatment of localised areas also reduces costs as compared to pre-treatment of the entire surfaces of the components.

Claims

1. A method of preparing the surface of a component for bonding to another component comprising the steps of: applying a pre-treatment solution onto localised areas of the surface from first application means moving across the surface; allowing the pre-treatment solution time to treat the surface and to dry; and applying adhesive onto the pre-treated areas of the surface from second application means moving across the surface.

2. A method as claimed in claim 1 in which a plurality of pre-treatment solutions are applied onto the localised areas from a series of application means which move across the surface in succession.

3. A method as claimed in claim 1 or 2 in which the component is formed from aluminium sheet.

4. A method as claimed in claim 3 in which the pre-treatment comprises a chemical conversion process.

5. A method as claimed in claim 3 in which the pre-treatment produces a surface layer on top of an air-formed oxide layer on the aluminium, the surface layer containing at least 5% by weight of chromium.

6. A method as claimed in any preceding claim in which the adhesive is applied in a powdered form.

7. A method as claimed in any preceding claim in which the adhesive is applied less than 60 seconds after the completion of the pre-treatment process.

8. Apparatus for preparing the surface of a component for bonding to another component in accordance with the method of claim 1 comprising drive means for moving a plurality of application means across the surface of the component, first application means being arranged to apply a pretreatment solution onto localised areas of the surface and second application means being arranged to apply adhesive onto the pre-treated areas of the surface.

9. A method substantially as hereinbefore described with reference to the examples given.

10. Apparatus substantially as hereinbefore described with reference to the examples given.