The metal frame of a car or light truck has an extremely complex shape. Many areas are hidden from a direct line of sight. It is virtually impossible to coat such a complex shape with conventional spray-applied paint. In order to achieve maximum coverage and therefore maximum corrosion resistance, this first coating layer is applied in a process known as electrodeposition. The metal body is electrically charged, then immersed in a bath containing oppositely charged paint particles. These particles are attracted to the metal surface, neutralized, and can then be baked into a coherent, tough film. Current practice favors making the vehicle body the cathode in this process (this minimizes corrosion for steel). These products are called cathodic electrocoats.
Requirements: Electrocoat products must exhibit high throw power (the ability to penetrate deeply into crevices) as well as excellent corrosion resistance. The electrocoat products need to be applicable on all substrates used in the automotive industry (steel, zinc coated steel, aluminum alloy etc.). The baking requirements must be compatible with the different customer needs, and the products must provide a smooth appearance. A new environmental requirement requires that the electrocoats must function without the addition of heavy metals such as lead and in some areas in Europe also without tin.
DuPont Electrocoat Products: DuPont Automotive Systems offers a complete line of electrocoats including both lead and tin free coatings, HAPS-free systems as well as special properties like improved edge protection, low bake, improved throwing power or weather durability.
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Requirements: The primer layer is the coating layer that joins a corrosion-protected substrate to the topcoat. It functions to smooth out surface irregularities, improve stone-chip performance, and helps to protect the substrate from visible and UV light. The primer must be capable of reliable and uniform application, and should contribute a minimal environment footprint. Today’s primers include solventborne, waterborne and powder forms. Color-keyed primers are often used to allow minimum basecoat film thickness, to optimize the painting process and to minimize defects related to stone-chip damage.
DuPont Primer Products: DuPont Automotive Systems offers a complete line of primers including solventborne, waterborne, water slurry and powder as well as 2K waterborne. The VOC of water slurry primers is less than 0.4 lbs/gal (48 g/l). DuPont Automotive Systems frequently recommends specific primer combinations with topcoats to optimize application robustness and field performance. Depending on customer demands and primer system, an amazing variety of colors can be realized to minimize the need of basecoats on interiors. If needed, a low cost conversion waterborne primer (LCC) can replace solventborne primers with minimal modifications to application facilities. This is an easy way to meet newest VOC legislation requirements.
Environmental regulations force the automotive industry to reduce solvent emission in their paint shops. In conventional paint solvents discharge into the air during the drying process. Options to meeting environmental regulations are Powder coatings, which contain no solvents.
Requirements: The powder clearcoat technology for OEM paint shops was developed in the early 1990s. This technology is emission free. It is based on Acrylic binder chemistry.
Powder Primers have become a mainstay for some OEM manufacturers. They provide the required protection and prepare the surface for topcoating without the use of solvents
DuPont Powder Products: The main properties of powder clearcoat, besides being emission free, are a very smooth and glossy surface and excellent resistances against weathering, chemical and scratch influences. Acrylic binders ensure OEM requirements such as weathering stability or chemical resistance.
DuPont also offers hybrid powder primers to meet the requirements of OEM automotive companies. This product offers excellent application robustness and meets today's stringent durability requirements.
Requirements: Basecoat is the coating layer that provides color and aesthetic effects. Basecoat must provide uniform appearance initially and for many years without fading. Modern requirements for appealing vehicles often require micas, aluminum flakes and other effect pigmentation. These can be incorporated in one basecoat layer or in a separate layer (for example in two-tones). If two basecoat layers are used, the sandwich with the clearcoat is called a tricoat topcoat. DuPont Automotive Systems is the world leader in wet-on-wet tricoat application in both solventborne and waterborne basecoat topcoats.
DuPont Basecoat Products: DuPont Automotive Systems offers a complete color palette in solventborne and waterborne basecoats. DuPont Herberts Automotive Systems has an extensive color styling effort and works closely with designers from all major automotive manufacturers. Styling options range from familiar solid colors through interesting metallics to eye-catching colors (color-movement effects).
Requirements: The clearcoat is the coating layer that forms the last interface to the environment. It carries the biggest part of the technological performance and must be able to resist environmental etch, bird droppings, car wash machines and other outside influences. To improve performance against all these influences, OEM coating systems move from colored topcoats to basecoat/clearcoat systems. The clearcoat in combination with the basecoat forms the automotive topcoat, which gives the vehicle its appearance. One and two component clearcoats (1K and 2K) are applied over both solventborne and waterborne basecoats.
The driving forces for clearcoat development are cost of material and process, appearance, etch and scratch resistance and the environmental footprint. Environmental pressures lead to an intensified development of super high solids, waterborne and powder clearcoats.
DuPont Clearcoat Products: Since the time when solventborne acrylic-melamine 1K systems were the predominant clearcoats, many technological improvements have been made. Requirements for long-term technological performance led to a portfolio of clearcoats that fulfill various customer demands. Product specifications are adapted to the application conditions in the different OEM plants, but are based on common chemical approaches and formulating principles.
Worldwide, approximately 80% of all passenger cars are coated with 1K clearcoats, and the remainder with 2K clearcoats. The 1K clearcoats are subdivided into solventborne acrylic melamine systems, clearcoats with enhanced etch resistance, high solid-systems, waterborne systems and powder versions. The 2K clearcoats include solventborne, super high-solids and waterborne versions.
DuPont Automotive Systems is the only coatings supplier that supplies every type of clearcoat system and is the leading global supplier of topcoats to the worldwide automotive industry.
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