PANEL REPAIRS
SEALING AND CORROSION PROTECTION
9
Underbody protection repairs
Whenever body repairs are carried out, ensure that
full sealing and corrosion protection treatments are
reinstated. This applies both to the damaged areas
and also to areas where protection has been
indirectly impaired, as a result either of accident
damage or repair operations.
Remove corrosion protection from the damaged
area before straightening or panel beating. This
applies in particular to panels coated with wax, PVC
underbody sealer, sound deadening pads etc.
WARNING: DO NOT use oxy-acetylene gas
equipment to remove corrosion
prevention materials. Large volumes of
fumes and gases are liberated by these materials
when they burn.
Equipment for the removal of tough anti-corrosion
sealers offers varying degrees of speed and
effectiveness. The compressed air-operated scraper
(NOT an air chisel) offers a relatively quiet
mechanical method using an extremely rapid
reciprocating action. Move the operating end of the
tool along the work surface to remove the material.
The most common method of removal is by means
of a hot air blower with integral scraper.
NOTE: High temperatures can be
generated with this equipment which may
cause fumes. Take care during its use.
Another tool, and one of the most efficient methods,
is the rapid-cutting ’hot knife’. This tool uses a wide
blade and is quick and versatile, able to be used
easily in profiled sections where access is otherwise
difficult.
Use the following procedure when repairing
underbody coatings:
1. Remove existing underbody coatings.
2. After panel repair, clean the affected area with
a solvent wipe, and treat bare metal with an
etch phosphate material.
3. Re-prime the affected area.
CAUTION: DO NOT, under any
circumstances, apply underbody sealer
directly to bare metal surfaces.
4. Replace all heat-fusible plugs which have been
disturbed. Where such plugs are not available
use rubber grommets of equivalent size,
ensuring that they are embedded in sealer.
5. Mask off all mounting faces from which
mechanical components, hoses and pipe clips,
have been removed. Underbody sealer must
be applied before such components are
refitted.
6. Brush sealer into all exposed seams.
7. Spray the affected area with an approved
service underbody sealer.
8. Remove masking from component mounting
faces, and touch-in where necessary. Allow
adequate drying time before applying
underbody wax.
After refitting mechanical components, including
hoses and pipes and other fixtures, mask off the
brake discs and apply a coat of approved underbody
wax.
NOTE: Where repairs include the
application of finish paint coats in the
areas requiring underbody wax, carry out
paint operations before applying wax.