77
PANEL REPAIRS
8
SEALING AND CORROSION PROTECTION
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 both 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, to avoid distortion it is recommended that
the joint be gently heated until the bonds weakens
sufficiently to permit panel separation.
NOTE: Spot welding through
metal-to-metal adhesive is feasible, but
take special 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 seam sealing after the application of primer
and before the surfacer and final paint coats. Ensure
that surfaces are first cleaned of all grease and oil.
Apply the sealer material to the joint as a bead, either
by hand or using an applicator gun. Brush sealer well
into the joint and wipe smooth using a cloth soaked
with solvent such as Shell SBP3. This will ensure an
acceptable cosmetic finish.
Apply sealer to ALL accessible joints following repair
work. Be aware that damage to a vehicle can often
result in deflection to those areas of the body which
are remote from the impact. The sealers in these
areas can therefore be disturbed by subsequent
straightening and repair operations. Check joints in
the vicinity of the area undergoing repair for evidence
of cracked sealer, clean them out as required and
re-treat them with 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 acid-etch
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, apply the sealer to both
sides of the repair joint. Where access is limited to
one side only (e.g. box sections), inject the affected
box member with cavity wax.
CAUTION: ALWAYS deploy an extractor
unit to remove toxic fumes when using
oxy-acetylene equipment to remove panels
treated with wax and sealers.
Sealing Water Leaks
Sealing charts in this section show those areas of the
bodyshell most likely to be affected by accident
damage and water leaks, and which could therefore
require re-treatment in repair. They do not show those
joint areas which only apply to factory assembly
operations and which are unlikely to be disturbed in
service (e.g. centre tunnel), or where the damage
would be so severe that the entire bodyshell would
normally be written off.
When water leakage occurs, always adopt a logical
approach to the problem using a combination of skill,
experience and intuition. Do not attempt to reach a
conclusion based only on visual evidence, such as
assuming that a leak emanates from the windscreen
because the footwell is wet. It will often be found that
the source of the leak is elsewhere. The correct
procedure will increase the chance of locating a leak,
however obscure it may seem.