Ford Fiesta (2011 year). Manual — part 175

Aids

Cleaning putty

Cleaning putty allows deposits on the paint surface
to be removed easily and gently. The following
paint faults can be removed using cleaning putty:

• Metal deposits and iron dust.

• Paint or color mist.

• Tree resin and tar.

• Insect residues.

The surface to be worked must be thoroughly
cleaned before the cleaning putty can be applied.
Then the surface is sprayed with soapy water. Now
the cleaning putty can be slid over the surface until
all unevenness is removed.

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Painting Plastic Parts

General

Although these days plastics can be produced in
all colors and with a matt or gloss surface, painting
is often necessary.

NOTE: Manufacturer's limitations concerning the
feasibility of painting certain components must
always be observed.

Reasons in favor of applying paint to plastic are:

• Individual coloring, matching the body paint.

• More gloss and color brilliance through painting.

• Removal of production imperfections.

• Protection from atmospheric exposure.

Nowadays painting plastic presents no problems
because the materials are known and matched to
the paint. In order that the painter can use the
correct painting materials, the type of plastic must
first be correctly determined.

To allow this, plastics are marked on the rear in
accordance with the recommendations of the
Association of Vehicle Manufacturers.

Once the type of plastic is determined it is an easy
matter to assign special paint recommendations,
matched to that particular plastic. Unmarked
plastics require knowledge of materials so that a
correct choice of paint materials can be made and
the component can be reliably painted.

Plastic groups

Thermoplastics

When warmed these undergo a reversible
transformation into a plastic deformable state and
once cooled they maintain their shape. They
consist of string-like (linear) or only slightly
branched molecular chains.

Thermosets

Thermosets are hard and have the form of a
close-meshed network in all directions. They do
not undergo plastic deformation, are especially
resistant to chemicals, are difficult to swell and are
insoluble. At normal temperatures they are hard to
brittle. At first the material does not undergo any
change when heated, but when it reaches a critical
point, the thermoset is totally destroyed.

Elastomers

Elastomers are characterized by high elasticity
over a wide temperature range. They have
properties like rubber or a sponge and after
compression or distension they return to their
original state.

Types of plastic

The plastics used in the automotive area:

• ABS - Acrylonitrile butadiene styrene (polymer)

• PA - Polyamide

• PC - Polycarbonate

• PE - Polyethylene

• PP - Polypropylene

• PP/EPDM - Polypropylene/ethylene propylene

diene copolymer

• PC/PBT - Polycarbonate/Polybutylene

terephthalate

• PBT/PC - Polybutylene

terephthalate/Polycarbonate

• PUR - Polyurethane

• GRP - Glass reinforced plastic

NOTE: PE and PP are plastics which cannot be
painted, or can only be painted using special
techniques.

As well as the pure plastics, so-called 'blends' are
also used. This means combinations of different
plastics. If we were dealing with metals they would
be called alloys.

Plastic identification

Normally the identifier is marked on the plastic
components used in vehicle construction.

One method to determine the plastic group is the
sanding test. In this a place is chosen which will
not be visible later, and the finger belt sander is
used to sand the plastic.

The plastic group can be determined using the
pattern left by the sanding and the dust:

• Thermosets produce a white dust.

• Thermoplastics smear and do not produce dust.

The plastic group can be determined by a sound
test:

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• Degree of hardness - the higher-pitched the

sound, the harder the plastic.

• Elasticity - the more muffled the sound, the

higher the elasticity of the plastic.

Cleaning plastic

Plastic components are manufactured using
complicated moulds and presses or other highly
engineered tools, mostly using an injection
moulding process or reactive injection moulding
process.

In order to be able to remove the component from
a particular tool, a separating agent is used, which
in some cases adheres very strongly to the plastic.

This separating agent on the plastic components
must be completely removed before any surface
coating is applied.

Warm storage (tempering) before actual cleaning
brings the following advantages:

• The separating agent sweats out of the plastic.

• Tensions in the plastic are released.

• Air inclusions can be recognized and removed.

Intensively clean the item several times using a
pad and fresh cleaning agent.

NOTE: A single wipe, even with cleaning agent, is
not usually sufficient in most cases. Clean textured
components with the aid of a soft brush.

After cleaning, it is absolutely vital that cleaning
agent absorbed by the plastic should be expelled
by tempering again. If the ventilation is good and
the room temperature is about 20°C the solvent
can be evaporated away by overnight storage.

Painting new components

It is absolutely vital that the substrate of an
unpainted new component is free of separating
agent. Paint can only be applied directly to very
few plastics. The plastic must first be identified
exactly and then worked with a repair system which
is matched to the type of plastic. In most cases a
plastic etch primer must be applied as adhesion
base to all plastics which can be painted.

NOTE: Plastics have a tendency to become
electrostatically charged. This can easily cause
contamination during painting. Special antistatic
cleaning cloths prevent electrostatic charging.

Work process for thermoplastics:

• Thoroughly clean the surface.

• Temper the plastic.

• Afterwards clean with antistatic cleaner or

antistatic cloths.

• Apply the bonding agent.

• Apply elastic filler. After it has dried, sand and

clean.

• Apply one coat Uni-paint with elasticizer

additive. For two layer painting the elasticizer
additive is in the clear lacquer.

NOTE: Follow the paint manufacturer's guidelines
during all work.

Work process for thermosets:

• As a rule, thermosets can be handled in the

same way as normal body components.

Work process for PUR soft foam:

• The work process is the same as for

thermoplastic.

• Instead of using bonding agent, a filler wash is

applied to close the pores of the PUR soft foam.

The primer which has been applied to a primed
new component can vary greatly. If no
manufacturer's data is available, the composition
and suitability for further working must be tested.

Painted components with an already ascertained
and intact paint coat present no problems for
possible repainting. After sanding and careful
cleaning with plastic cleaner or thinners, painting
can be done directly.

Unknown primer

When dealing with unknown substrates it is
important to carry out an adhesion test on the
existing paint before any repainting is attempted.
First of all a mechanical test must be carried out,
for instance using a lattice cut and tear-off band.
If the adhesion of the old paint is not acceptable,
it must be mechanically removed and new paint
finish applied.

If the adhesion is acceptable, then an etch test is
performed using 2-component thinners. If no
etching can be detected in this test, application of
the the paint finish can be started directly.
Otherwise the old paint must be removed and a
new paint finish created.

With the help of universal or special plastic primers
and with only a few materials complementary to
those previously present anyway, the painter can
now apply a long-lasting paint finish to all popular
vehicle attachments made of plastic.

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Paint faults on plastic substrates

NOTE: Paint faults are fully described in the
chapter Paint Defects and Damage.

The most common paint faults which can occur
when painting plastic components and the methods
of repair are briefly described.

Discoloration

Cause/damage pattern:

• Plastic material is not suitable for painting.

• Incorrect bonding agent.

• Paint used not solvent resistant.

Repair of damage:

• Repaint using suitable materials.

• Install a new unpainted component.

Softening

Cause/damage pattern:

• Substrate not carefully cleaned.

• Air humidity too high or working temperature

too low.

• Drying time incorrect (too short).

• Materials for substrate not correctly matched to

each other or not mixed correctly.

Repair of damage:

• Dry out, sand, re-isolate and paint.

• Sand away faulty paint coats and re-apply paint

finish.

Paint damage caused by detachment, poor
adhesion

Cause/damage pattern:

• Insufficient paint adhesion between top coat

and filler. The whole of the paint finish detaches
from the plastic.

• Plastic not cleaned sufficiently, not or

inadequately tempered.

• Unsuitable cleaning agent or materials used.

• Poor or lack of intermediate sanding.

• Paint finish underbaked or overbaked.

Repair of damage:

• Sand away faulty paint coats and re-apply paint

finish.

Paint damage caused by blisters, craters,
sink holes

Cause/damage pattern:

• Painting on PUR plastic which was not painted

in production.

• Surface of the plastic material too porous.

• Flash-off time not adhered to.

• Drying temperature too high.

• Moisture in plastic material.

• Layers too thick.

Repair of damage:

• Clean the damaged area, sand, re-isolate and

paint.

• Remove the paint layers and re-paint.

Crack formation

Cause/damage pattern:

• Overexpansion of painted PUR plastic

components.

• Use of unsuitable paint materials.

• Paint materials not suited to each other or

incorrect mixture ratio.

Repair of damage:

• It is not possible to repair overexpanded PUR

plastic components.

• On other plastics, sand away damaged layers,

isolate and repaint.

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