The history of serial painting
The pink Ford in the article picture has certainly not been painted in series. But with Ford the first assembly lines started, and with it also the series painting. So what was suddenly different? A quick look back. In the pre-assembly time, utility items such as furniture or carriages and the first cars were painted individually and by hand with brushes or rollers in many layers.
Manual painting too slow
In addition, the drying of linseed oil took quite a long time – too long for mass production. Each part was painted individually, usually after assembly. With the start of the larger series and quantities, something new had to be considered, because both the application and the paint chemistry were not efficient enough.
Very fast drying nitrocellulose lacquers were developed, which had to be applied in many layers due to the low solid content. They also required a complex polish to achieve a high-gloss finish. The alkyd resin or synthetic resin lacquers developed at the same time (end of the 1920s) then brought the breakthrough for serial coating.
Series coating in Europe
The principle of monochrome was also continued with the introduction of this technology in Europe by Opel with the green tree frog (4 HP). Production of the Citroën 5CV had already begun in 1919 – in lemon yellow. The design of the Opel was so reminiscent of the Citroën that the proverb “The same thing in green” was probably born.
Today unimaginable, where everything strives for individualisation and multicolour paintwork with different colour tones on the roof and other parts of the vehicle is no longer a rarity. However, this feature can only be achieved with today’s quantities through a high degree of automation and digitization.
Colour trends in car paints
For many years the colours have been subject to trends and the paint manufacturers try to emphasise the design of the cars and follow the general trends with always new effect colours or colour worlds. Porsche made white cars socially acceptable about ten years ago. Previously unthinkable, that was the colour of cheap vans or service cars. In Japan, however, a very often desired, because clean, colour. So culture also plays an important role.
Apart from the colour, there have also been some changes in coating technology in recent decades. From alkyd coatings to acrylates, which were also processed as two-component coatings. Then the switch to water-based systems, first in the base coat area, later also in the clear coat area. Today, most OEM automotive coatings are aqueous. The changeover, especially for application technology, was enormous. 2K spraying systems for isocyanate crosslinked systems were developed, and in the last ten years fully automatic, robotic application has also established itself.
Fewer paint layers
This already makes us very efficient today, but the process is to be further streamlined with new technology. Single-layer systems are the wish of many – actually since Ford. Unfortunately, this has not yet been possible in the desired quality, but this will certainly change at some point.
Because paintwork is important for every source of energy in cars. However, the trend towards a “shared economy” could greatly reduce the colour palette again. If I can always summon a car when I need one, it no longer has to meet my individual visual requirements. It has to be more functional and appeal to a wide audience – even if it’s not likely to be pink or black.
The textbook Automotive Coatings Formulation from Ulrich Poth deals with the composition and the production of the most difficult components as well as their physical and application technology characteristics.