The World Premiere Of A New Innovative Nano-Particle Clearcoat
Published: 4th December 2003
Considerably greater paint gloss after extreme test in laboratory car-wash
Mercedes-Benz began by testing the impressive scratch and chemical resistance of nano-particle clearcoat on individual body parts in the laboratory, before sending out more than 150 test cars as part of a practical testing programme in the summer of 2001. The results were extremely encouraging. After several years of testing, the nano-painted Mercedes test cars stood out from vehicles with conventional clear lacquer with their significantly higher level of paint gloss. This conclusion was backed up by standardised tests carried out in a laboratory car-wash according to DIN standards, in which a precisely calculated measure of fine quartz sand is mixed in with the water. This test thus provides an accelerated simulation of the processes in a regular car-wash: according to the amount of dirt on the car, 10 cycles in the lab car-wash reproduce the degenerative effect of 50 to 100 regular car washes.
After the wash programme, the engineers use a special gloss measuring device to examine the scratch marks on the painted metal plates and assess the residual gloss. The results showed that whilst the residual gloss of conventional paintwork stood at around 35 per cent after 10 wash cycles in the laboratory car-wash, the more scratch-resistant nano-particle clearcoat gave a reading of 72 per cent.
Resistance three times higher in the "nano-scratch" test
The Research Institute for Pigments and Paints (FPL) in Stuttgart, which worked closely with Mercedes-Benz in the testing programme for the new clear lacquer, supplied a nano-scratch testing device which allowed the engineers to make a precise examination of the nano-structure of the paint surface. This state-of-the-art piece of equipment is fitted with a diamond point measuring two micrometres, which is passed over the paint sample according to a pre-defined scale of gradually increasing force and leaves behind an extremely fine scratch mark on the paint.
Experts then analyse the paint surface under the Atomic Force Microscope and take a series of measurements, including the force required for the first cracks to appear in the paint structure.
Cracks begin to form in the nano-particle clearcoat when a force of 20 millinewtons (mN) is exerted, whilst the diamond point breaks through conventional paint with only 7.4 mN of force. This scientific test thus provides further evidence of the significantly greater scratch resistance of Mercedes-Benz’ nano-particle clearcoat.
Mercedes demands a high level of chemical resistance
Mercedes engineers also assessed the chemical resistance of the innovative clear lacquer using standardised procedures. As part of the testing programme, samples of four different substances -- sulphuric acid, pancreatin (simulating bird droppings), tree resin and fully desalinated water -- were dripped onto the paint surface in rows and left to work their way in over a period of half an hour and in temperatures of 30 to 75 degrees Celsius. The engineers then assessed from what temperature the paint surfaces began to show signs of lasting damage, with target values pre-calculated for each substance. In this test, the newly developed nano-particle clearcoat fulfils the same stringent Mercedes quality criteria as conventional paint systems.
The new nano-particle clearcoat has also passed other extreme tests – such as extended exposure to ultraviolet light mirroring the intensity of the sun in the US state of Florida – which prove its readiness for series production in every respect.
