Sealants and adhesives

SEALANTS AND ADHESIVES

Structural Adhesive

Metal-to-metal adhesive is applied to critical joint areas during factory assembly. The material used is a high-temperature, heat cured, nitrile phenolic which serves to bond two metal surfaces and also to seal the joint against ingress of dust, water, petrol and fumes. This material is not suited for service use, and should be substituted in repair using a suitable medium strength adhesive.

When separating a joint treated with metal-to-metal adhesive, it is important to avoid distortion. Heat the joint gradually until the bond weakens sufficiently to permit panel separation.

NOTE: Spot welding through metal-to-metal adhesive is feasible, but take particular care to adjust the transformer setting to ensure a reliable weld. DO NOT carry out MIG welding on a joint area which has been treated with metal-to-metal adhesive until all traces of adhesive have been removed.

Seam Sealers

A heat cured, PVC Plastisol sealer is applied to joint areas during factory assembly. This material is not suitable for service use.

Carry out all seam sealing after the application of primer, and before the surfacer and top coats. Ensure that all surfaces are first cleaned of all grease and oil. Apply sealer materials to the joint as a bead, either by hand or using an applicator gun, and brush well into the joint. Following application, smooth the sealer with a cloth soaked with solvent such as white spirit or Shell SBP3. This will ensure an acceptable cosmetic finish.

Ensure that ALL accessible joints are sealed following repair work. Note that damage to a vehicle can often result in deflection to those areas of the body which are remote from the impact. As a result the sealers in these areas may be disturbed by subsequent straightening and repair operations. Check all joints in the vicinity of the area undergoing repair for evidence of cracked sealer, then clean out as required and apply fresh sealer using the following procedure:

• Clean the affected joint or seam and re-treat any exposed metal areas with a suitable etch phosphate primer.
• Treat affected area with an etch-acid primer.
• Apply appropriate seam sealer as necessary.
• Apply appropriate colour coat (and underbody sealer as applicable).

Where joints are inaccessible following the reassembly or fitment of components, ensure that a paste-type sealer is applied to such joints. Certain seams also become inaccessible after the completion of panel repairs. In such instances the paint process should be carried out and sealers applied before final assembly.

Provided access is adequate, sealer must be applied to both sides of a repair joint. Where access is limited to one side only (e.g. box sections), the affected box member should then be injected with cavity wax. See this section.

CAUTION: In the interests of Health & Safety, always deploy an extractor unit adjacent to the work area to remove toxic fumes, especially if oxy-acetylene equipment is being used to remove panels treated with wax and sealers.