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! The paint on this car stops rust. 1960s American cars were first to have electrophoretic paint as an anti-corrosion primer.

an estimated 42000 metric tonnes of electrophoretic paint solids. BIG - during 2003, 42 million vehicles manufactured world wide requiring an estimated 42000 metric tonnes of electrophoretic paint solids.

structures require less than 1gm 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. Drag-out rinsed off with clean permeate Unpainted part Painted part + drag-out Painted part Dragged-out paint reclaim S From pre-treatment To oven Paint bath Permeate Drag-out Paint return from UF membrane Paint pumped to UF membrane UF Raw permeate I E 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!