Company profile: Auto paint

How much thought do you give to the paint when buying a car? Sarah Houlton finds out there is a lot of technology in those colourful coatings

There's a lot more to the paint on a car than simply its colour. It has to protect the car's metal and plastic components, it has to be extremely durable, and the colours of all the different parts must look the same. These issues throw up many scientific and technical problems, and a variety of career opportunities for chemists.

© BASF

Automotive coating 

BASF is heavily involved in the automotive coating field. Christopher Hilger started work at the company's coatings headquarters in Münster, Germany, in 1991, straight after getting his University of Mainz polymer chemistry PhD. Initially working in resin development and powder coatings, he moved over to the automotive coatings sector in 2003, taking over responsibility for the development of base coats for suppliers to the automotive industry. 'We supply coatings to the car manufacturers, and also the producers of bumpers and other plastic parts. These are coated in the same colour as the car, but the coating is done offline in the supplier's plant. The finished part is delivered to the manufacturing line, and put onto the car there,' he says. 'The main function of these base coats is decoration - the colour and the effect, such as metallic or pearlescent,' he says.  

A standard car coating system consists of an electrodeposition coating to protect the metal from corrosion, a primer providing resistance to stone chips and to prepare the surface for the base coat which gives the decorative effect, and then a clear coat on top which provides durability. 'As with any other coating system, the colours have to perform well, and for a car this is particularly important. For example, it mustn't fade in sunlight even after many years,' he explains.  

An additional challenge is that the colours on the different parts of the car must match. 'It is a real challenge ensuring colour harmony between the parts that are coated off line, such as the plastic bumpers made by suppliers, and the metal of the car body itself,' he says. Yet the coatings for the various parts of the car are often very different - they might be water-borne or solvent-borne, or designed to coat metal or plastic. This means the formulation changes between different substrates, which can have a dramatic effect on the colour. 'We have a lot of experience in techniques such as colour measurement - it's essential if the colour of all the parts of the car is to look the same,' he says. 

Additives and binders 

Colour matching isn't the only challenge when coating the different materials used in a car - another is getting them to adhere to the surface properly, and the different layers of coatings to each other. This is the focus of Audree Andersen's work. A Quebec native, Andersen moved to Germany to study a decade ago, and after a PhD and postdoc at the Max Planck Institute for Interfaces and Colloids in Potsdam, she joined BASF in Münster in 2006.  

'I work in the research department in a competence centre on adhesion,' she says. 'Automotive paint has many layers, and often the adhesion between them can be poor. We are trying to understand the mechanisms involved in the adhesion, and improve it, as well as developing new chemistry in terms of additives and binders.' 

Every layer is different, and the chemistry varies, and along with it the mechanism of adhesion. 'Adhesion problems can result from chemical or mechanical difficulties, delamination between the layers or even a cohesion break within a single layer,' she says. 'Coating formulations are very complex, and we need to understand which parts of the formulation aid adhesion - and which prevent it.' Additives to prevent, say, light or weather damage can wreck the paint's adhesive qualities.  

Perhaps the biggest challenge she's faced - and is still working on - is trying to adhere a water-borne basecoat onto polypropylene bumpers. 'The plastic is very hydrophobic, and the paint very hydrophilic,' she says. 'A plastic pre-treatment such as oxidation usually ensures the paint sticks, but sometimes it doesn't work. If we don't know the exact recipe of the polymer, it's a real challenge trying to make something stick to a surface whose precise composition we don't know.'  

Hilger moved out of technical development into marketing last year, and is now a product manager for automotive coatings. 'I look at product lifecycle, product portfolio, and the performance of our products in the market,' he says. 'The team includes several people with a more commercial background, but I contribute from my technical perspective. We believe this gives a good mixture.' 

Sarah Houlton is a freelance writer based in Boston, US