Preparation by using paint
Remover
If the existing paintwork is in poor condition, or if
the damaged area is so extensive that the remaining
paintwork on the damaged panel is not worth rubbing
down, the existing finish can be removed with
paint remover. The first task is to remove any
flashes or chrome strips that can easily be removed.
If the work is being carried out in a shop where several
vehicles are being refinished, it is advisable to
store these fittings in boxes which should be
Figure 17.48Festo dust extractor (Minden Industrial
Ltd )
Figure 17.49Air driven polisher with foam pad
(Desoutter Automotive Ltd )
Automotive finishing and refinishing 601
labelled with details of the car such as customer’s
name, registration number and type of car. On a
complete refinishing job it is also advisable to label
each part to indicate from which side of the vehicle
it was removed. Should it prove to be too difficult
or impractical to remove any parts, these should be
masked completely. Though it is not always necessary
to mask the surrounding areas when stripping,
it is advisable to do so because if any paint remover
accidentally came into contact with an adjoining
door or bonnet, damage to these areas would occur.
However, if masking paper is applied it should be
of a fairly stout nature and laid in two or three
thicknesses to ensure that any paint remover accidentally
deposited on it does not immediately penetrate
to the paintwork beneath.
Paint removers were formerly of a highly flammable
nature and constituted a fire risk, but
nowadays non-flammable types are available and are
widely used. As well as removing fire risks they also
evaporate at a much slower speed; hence they remain
wet for a longer period and so have better penetration
properties. Though they are quite easy to use, some
precautions should be taken when working with
these paint removers. They can be a cause of dermatitis
by penetrating the pores of the skin, dissolving
the natural oils beneath and so leaving the pores
open to attack by bacteria. A simple precaution is to
apply a barrier cream to the hands before commencing
paint stripping, and to rinse off with water any
remover which comes into contact with the skin.
Strong rubber gloves are very useful when using liquid
paint removers. The operator should not smoke
when using paint remover, even though it is not flammable,
as it gives off a strong vapour which, on coming
into contact with a naked light, becomes toxic in
nature. This toxic vapour if inhaled into the lungs
will cause dizziness, nausea, and even vomiting.
Adequate ventilation should be provided in any shop
where paint remover is used, for the same reasons.
A fairly liberal coat of stripper should be applied
to the surface and allowed sufficient time to penetrate
through the various layers of paint. The softened
paint is then removed with a stripping knife
and the surface washed down with a generous
quantity of water. Both the laying on and the washing
off of the stripper can be done with old or
cheap paint brushes. To assist the removal of paint
at awkward places, a wire brush is an invaluable
tool. Very often a layer of scum or a fine stain of
primer is left on the surface but this can be quite
easily removed with steel wool and water. It is
imperative that all traces of paint remover be thoroughly
rinsed off, otherwise it will cause damage
to any subsequent paint system applied to the job.
Preparation by using abrasive
Paper
Before the rubbing down of a local repair commences,
the whole panel should be thoroughly
washed down with a detergent to remove all traces of
wax polish. Nowadays nearly all wax polishes contain
silicones, which can create ‘pinholing’ in any
paint applied over them. Water miscible cleaning
solutions, which are normally used for degreasing,
are suitable for wax removal. Thorough rinsing with
water and drying should follow. The grade of wet-ordry
paper chosen to rub down the damaged area
depends very greatly on the degree of damage, but
normally 180 grade is suitable. The paper should be
folded and torn so that one-quarter of the length can
be removed (Figure 17.50). This is then attached to a
rubber rubbing block and the damaged area abraded
using a liberal quantity of water to keep the work
clean so that continual inspection can take place. The
rubbing down is normally carried out with a forward
and backward motion until the paint is removed and
a feather edge achieved. Should paint remain in
recessed areas, it can be removed with a wire brush,
coarse steel wool, or abrasive paper without the rubbing
block.
Figure 17.50Method of fixing abrasive paper into
rubbing block
As an alternative to rubbing down by hand, power
tools can be used to speed up the process. These can
be either electric or driven by compressed air. Those
which are electrically driven are used dry, but compressed
air tools can be used either wet or dry. The
latter types are generally favoured for lighter work
where damage to the paintwork is not extensive, but
the electric tools are most suitable where severe
rusting of the metal has occurred.
602Repair of Vehicle Bodies