Transcript 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!