mass point JAGUAR X308 1998 2.G User Guide

ZINC COATED PANELS
Description
Approximately 70% of the 'body in white' (BIW) mass is made up of zinc coated panels.
• NOTE: To maintain the protective qualities of the zinc trea tment, repairs to any damaged coated area must be made as
soon as possible after the damage has occurred.
All exterior skin panels, with the exceptio n of the roof, are double side zinc plated and this coating (nominally 7,5 microns)
provides two way corrosion protection. Should the outer layer of paint become chipped with the zinc coating remain intact,
the zinc will oxidize on contact with air and being impermeable, this coat of oxidation will prevent corrosion damage of the
base metal. If the outer layer of paint and the zinc coating become damaged, the zinc rather than the base metal will react
with the air and 'sacrifice' itself to corrosion as a 'sacrificial anode'.
Welding Preparation
Contamination of the weld with resultant reduction in joint st rength increase and increased electrode tip dressing frequency
will occur zinc coating is not removed. In exceptional cases where the zinc coating must remain intact, the tip pressure and
welding current should be increased by 10 to 20%.
Where 'resistance spot welding' is employed, the zinc coatin g should be lightly abraded away on the mating surfaces and
those in contact with the electrode tips. Do not remove more zinc coating than is absolutely necessary.
Before welding, a weld-through primer or inter-weld sealer should be applied, as detailed in the Body Sealing and
Preservation manual.
Where MIG welding is used as an alternativ e to resistance spot welding for plug and butt welds or due to limited access, the
problems caused by the presence of zinc coating are much the same, with the added complication of increased weld spatter
and nozzle contamination.
Body Fillers
Conventional polyester fillers do not adhere satisfactorily to zinc plated panels, it is ther efore important that only those
products specifically designed for this application are used and the manufacturer's recommendations are followed.
Refinishing
Use only those products approved by Jaguar Cars Ltd and exercise special care on zinc coated panels.
As replacement panels ar e supplied ready primed, the only bare metal that needs to be exposed are those areas prepared
for welding etc, as decribed in 'Welding Preparation. Where any part of a panel is dressed back to the bare surface, it should
be treated with a zinc rich primer compatible with the paint application system.
GENERAL PREPARATION OF PANELS
Removal of Panels and Welds
• NOTE: Where other components must be removed for access, refer to the relevant manual section for guidance. This is
particularly important where steerin g, braking, suspension, electrical and safety systems are affected.
Expose all resistance spot welds, using a ro tary wire brush fitted to an air drill or a hand held wire brush on those that are
not clearly visible (1).
WARNING: DO NOT BURN UNDERSEAL OFF. USE A 'HOT KNIFE' OR SUITABLE SOLVENT.
Cut out spot welds using a Zipcutter or Roto-Bor (2). At this point it may be necessary to cut out the bulk of the panel using