Mercedes coating comes up to scratch

The new Mercedes CLS Coupé, launched this week at the Geneva Motor Show, will come with scratch-resistant, nanotechnology-based paint as standard.

The new Mercedes CLS Coupé, launched this week at the Geneva Motor Show, will come with scratch-resistant, nanotechnology-based paint as standard.

The new clear lacquer top coat, which provides gloss and weatherproofing properties, is the result of a four-year collaboration between Mercedes and US-based automotive coatings supplier PPG Industries. Dennis Taljan, PPG’s global director for decorative projects, said existing scratch-resistant coatings ‘have no elasticity and would crack in the temperature extremes cars must withstand’.

Scratch-resistant coatings usually have a polymer or resin basis in which the molecules strongly cross-link. But usually, the more dense the cross-linking, the more brittle the coating becomes.

PPG’s new coating, called Ceramiclear, is based on a polymer that cross-links strongly but remains elastic. But most of the scratch resistance is due to the presence of nanoparticles of a ceramic material, which rise to the surface when the paintwork is baked, merging into the cross-linked structure to provide a hard surface.

In the past adding nanoparticles to a coating has tended to make it go hazy. Getting the size and orientation of the nanoparticles right was crucial in making the process work.

Most paintwork scratches are caused by minute particles of dust or sand that become lodged in car wash brushes. After 40 cycles in a car wash, scratches on a vehicle using the new paint were about half the width and depth of those in conventional paintwork. The coating retained 80 per cent of its gloss compared to 20 per cent with a standard clearcoat.

It will also protect against degradation due to ultraviolet radiation or salt and chemicals, but not deliberate vandalism.

The new coating did not necessitate any changes in Mercedes-Benz’s production process or add to the emissions produced. The technology is being introduced on the E, S, CL, SL, SLK and the new CLS-class, before being extended to the car maker’s complete range.

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