Download Slide 1

Electrophoretic application of paint.
Peter Hope, FIMF
LVH Coatings Ltd.
Electrophoretic painting – what is it?
• Target surface must be electrically
conductive.
• Target is immersed in the specially
formulated water-based paint bath and a
d.c. voltage is applied.
• Paint solids are electrodeposited
conformally over conductive surfaces.
• Similar to electroplating – but depositing a
paint instead of a metal.
Why would you consider the
electrophoretic application method?
• Your (conductive) widget is a complicated
shape that is difficult to paint any other
way.
• Complete and controlled surface coverage
is necessary for decoration and/or
performance.
The paint on this car stops rust.
It must be
Electrophoretic!
1960s American cars were first to have electrophoretic paint
as an anti-corrosion primer.
BIG - during 2003, 42 million vehicles manufactured world wide requiring
an estimated 42000 metric tonnes of electrophoretic paint solids.
Fibre length = 6mm
Fibre radius = 3.5 microns
Tip radius = 50nm
SMALL - 2000 to 2008: Electron microscope probes and other micro-research
structures require less than 1gm of electrophoretic paint solids!
SMALL items - but large numbers: Spectacle frames….
……Door and window hardware….
… various other complex-shaped consumer items…..
…and difficult-to-paint industrial components….
…..Automotive functional parts:
….Automotive trim parts…
…..Specialist architectural.
Process advantages.
• Very suitable for painting complicated
shaped items.
• High productivity – especially when
automated.
• High material utilisation/low wastage
compared to other application methods such
as spraying.
Electrophoretic vs.
Spraying:
Overspray wastes
material.
Can be labour
Intensive.
Rack/support gets
coated also – waste
of material.
Electrophoretic application enables very high transfer efficiency.
Simple electrophoretic paint line schematic.
Unpainted part
Painted part + drag-out
Drag-out rinsed off
with clean permeate
Dragged-out
paint reclaim
S
S
From pre-treatment
S
Painted part
S
S
To oven
Paint bath
Permeate
Drag-out
Paint return from
UF membrane
Paint pumped to
UF membrane
UF
Raw permeate
IE
Clean permeate
Using ultrafiltration (UF) rinse/reclaim closed loop:
- nearly 100% material utilisation with minimum waste.
Appropriateness of use.
(= “disadvantages”)
• Mainly suitable for large continuous
production quantities of a single finish.
• Requires investment in specialised plant
and equipment.
Continuous R&D produces an increasing number of
Electrophoretic painting capabilities…..
Equipment/installation.
• Basic requirements are a coating bath,
rectifier, filtration, purified water and a
curing method.
• Bath size and installation footprint
depends upon the size and production rate
requirement of the widget.
• Bath sizes vary from less than 100 litres to
more than 500000 litres.
• Easily incorporated into electroplating lines
Curing methods.
• Thermal curing is possible from about 80C
up to about 190C. Thermal curing below
about 120C tends to limit the potential for
high chemical resistance.
• Both hot air and Infra-Red techniques are
used for thermal curing.
• UV curing systems are available that can
be processed below 80C.
Hardness, wear resistance
and friction control.
• Hardness and wear resistance can now be
comparable with brass and aluminium by
using nanocomposite technology.
• Incorporation of various dry film lubricants
provides highly wear resistant low friction
coatings.
Corrosion protection.
• Electrophoretic paints can provide all-over
corrosion protection for most metals.
• Good compatibility with most “traditional”
and new anti-corrosive pre-treatments.
• Certain instances do not require the use of
any separate anti-corrosive treatment –
notably anodic electrophoretics over some
aluminium alloys.
Chemical resistance.
• Different resin systems are available that
will cover many industrial requirements.
• Automotive grades – based on epoxies –
have intrinsically high chemical resistance.
Resistance to weathering.
• The main problems are resin breakdown
and colour change due to the effects of UV
radiation in sunlight.
• Exterior durable resin systems are
available with compatible fade-resistant
colourants as required.
Decoration.
• Electrophoretics can be coloured in a wide
variety of effects similar to “conventional” paints.
Even “metallic” or pearlescent effects are
possible to some extent.
• A characteristic is the incorporation of
transparent colourants to give coloured metal
effects over reflective “white” substrates such as
bright nickel or polished zinc and aluminium.
• Gloss can be controlled independently of colour
effect.
Other capabilities.
• Photoresists: – 2D or 3D surface imaging
for printed circuits, nameplates and
chemical milling.
• Conductive coatings: - grounding,
shielding, anti-static and multi-layer
electrophoretic coating.
• Something else? Ask and you might get!
Electrophoretic summary.
• Mature and accessible industrial painting
process.
• Especially appropriate for complicated shapes in
high production quantities.
• Very wide capabilities – general purpose to
highly specialised.
• Ease of automation minimises unit costs by high
productivity.
• High material utilisation with minimal waste.
Thank you for your attention!