Technological Trends
Future Expectations, Trends And Development Strategies In Automotive Coating
The future expectations in automotive OEM industry can be classified in three groups. Possible developments that satisfy these expectations can sometimes interwine, and thus one development can satisfy more than one expectation.
Based on the customer expectations, the future developments for automotive OEM industry can be summarized in above Scheme.
A. Expectations for the appearance and performance of the paint film:
Recently in the past, investigations1 were made in Europe, Japan and USA via internet to identify the expectations of automotive users from their car paint. The most important criterion was found as the performance with 48%, followed by color with 33%, having a shiny and attractive color and being manufactured with environmental friendly technologies were the other criteria. It was concluded that the primary expectation of automotive users is an increased performance of the car paint film.
Increasing the scratch & mar resistance, stone chipping, dust slipping and chemical resistance performances of the paint film will satisfy the expectations of the final users. Improvement of these performances can be achieved by using more densely cross linked and nano particle controlled clear coats.
It was also concluded that the users have expectations about the color and esthetical appearance of the paint film. Pigment producers continuously work on producing pigments having new color effects. Though the expectations of the final users are satisfied, the cost of the paint increases by using newly developed pigments. Besides color, the combination of distinctness of image (DOI) and leveling properties should also be taken into account when the esthetic of a paint film is discussed. The appearance and the paint transfer efficiency can be improved by using high speed rotational bells having high spraying flow rate.
Environmental friendly coating expectations can mainly be satisfied in two ways. First is the elimination of using heavy metal components in coating formulations, and the second is to switch to waterborne coatings in order to reduce ozone formation.
B. Expectations for increased coating efficiency and decreased coating cost:
Efficiency can be improved mainly in two ways. The first one is the 3 Wet application process. In this process; primer, basecoat and clearcoat are applied wet on wet in sequence. In current practice, after the primer is applied and cured in a separate oven, the basecoat and clearcoat are applied wet on wet and both cured together. The operational cost and CO₂ emission will be decreased due to saving of energy in 3 Wet application by eliminating the primer oven.
VOC emission will be further reduced by using waterborne primers. Some technical problems can be expected when waterborne basecoat is applied wet on wet with waterborne primer. The interpenetration of the both waterborne layers should be avoided, and the orientation of special effect pigments in basecoat should be controlled. Most of these problems are already solved by research and development activities of paint producers.
* Typical 3 Wet Application Process can be figured as below
Further developments to eliminate the first pre-heating process are going on.
Painting car body parts separately can improve efficiency and also leveling that contributes the esthetic appearance of the paint film.
* The schematic representation of separate parts painting process can be shown as below
- Smaller cabins can be used which leads considerable energy saving.
- More surfaces can be painted horizontally, as a result better appearance of paint film will be achieved.
- Spraying equipments can be changed and their cost can be reduced.
- Painting process can be shortened considerably by UV painting. Higher cross linking density and faster curing are achieved in UV curing paints, which lead to increased scratch resistance of the paint film. There is not much data about stone chipping and long term durability performance of the UV paints and this is the greatest uncertainity that limits their applications. UV technologies should also be developed for colored coatings.
Color matching and application technologies need to be improved in order to be able to paint parts separately.
C. Expectations for reducing adverse effects of painting process on environment:
The adverse effect of painting process can be decreased by reducing CO₂ and VOC emissions and waste contaminants.
These adverse effects can be reduced by increasing efficiency as explained in previous paragraphs and by modifying current application technologies.
The basecoat and clearcoat can directly be applied on cataphoresis coated body by eliminating the primer layer which eases the application process and reduces the consumption of paint. Using powder slurry varnishes and applying water based paint for body parts will also improve current application technologies.
It should be noted that when the topcoat is applied on cataphoretic primer without a spray primer layer in between, the topcoat should be able to protect cataphoretic primer from UV light. Otherwise, aromatic epoxy resins in the cataphoretic primer will be degraded under UV light exposure which may cause delamination in paint layers.
Umemura, S., Suzuki, T., “Future Direction for 2010 Automotive Coatings”, 5th International Strategy Conference on Car Body Painting, 13-14 July 2006, Berlin
