The paintwork of a Mercedes Benz car thus consists of five layers with a combined thickness of some 100 micrometres (approx. 0.10 millimetres). Each of these coats is the result of a complex development process spread over several years which has seen a team of experts fulfil a number of requirements. In addition to refining the process technology involved, the engineers have addressed key issues relating to environmental protection, quality and durability.
The innovative nano-particle clearcoat, which Mercedes Benz will become the world’s first car maker to offer from the end of 2003, is a case in point, with over four years of development and testing behind it. The new clear lacquer has helped the engineers resolve the technical conflict of interests between scratch resistance and chemical resistance which has plagued the development of clear lacquer up to now. This new and innovative paint system meets Mercedes’ stringent standards in both respects.
Tiny ceramic particles each measuring a millionth of a millimetre form a protective layer
A large proportion of all paintwork scratches are caused by mechanical car-washes. Minute particles of hard materials, such as road dust and sand, become lodged in the rotating brushes and etch scratches into the paint surface. These "hair scratches" are particularly noticeable in darker paint shades.
With the help of the nano-technology developed at the beginning of the 1980s, scientists have been able to alter the molecular structure of the binding agent and integrate tiny, microscopic ceramic particles. These each have a diameter of less than 20 nanometres, which makes them tens of thousands times thinner than a human hair.
During the electrostatic paint application process, the binding agent particles float around freely at first in the liquid paint. It is not until the car body is placed inside the paintshop ovens at a temperature of some 140 degrees Celsius that the particles cross-link into a dense network. This allows the lacquer to provide much more effective scratch protection than conventional paints, whose binding agent and cross-linking agent form comparatively long molecular chains. Tests confirm that the tiny, microscopic ceramic particles do indeed enhance the scratch resistance of this clear lacquer several times over.
In other words, nano-particle clearcoat offers considerably greater and longer-lasting resistance to paint scratches – such as those caused by car-washes – than conventional paint finishes. However, even this new clear lacquer developed on the basis of nano-technology cannot provide effective protection against vandalism, i.e. if the paintwork is scratched deliberately using keys, tools or other objects.