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Products and solutions, 2003-09-09, 02:00 AM

Preprimed sheet: Organic coated steel for the auto industry

At the IAA 2003 Frankfurt Motor Show, ThyssenKrupp Stahl AG will be exhibiting a car door whose outer skin is made of sheet metal prepainted by the coil coating process. The coating performs the functions of both electrocoat primer and filler. The prepainted sheet therefore already has half of the paint system needed for body outer parts. The usual paint system applied by car manufacturers consists of primer, filler, top coat and clear coat.

The electrocoat primer serves to provide corrosion protection, while the filler provides mechanical protection against stone chipping etc. ThyssenKrupp Stahl AG applied primer and filler directly onto cold rolled, electrogalvanized and phosphated sheet in a continuous coil coating line. The process produces extremely uniform coatings of consistently high quality. The aim of the project is to supply the auto industry increasingly with prepainted sheet from coil.

In this way, customers can significantly shorten the process of painting outer body parts, especially as preliminary operations such as cleaning and phosphating are no longer needed. In addition, the capital burden for paint facilities is reduced. This initiative by ThyssenKrupp Stahl AG has interesting implications above all for automotive suppliers who have to deliver parts and modules in the respective car color. Because paint facilities are too expensive for suppliers to finance, they often turn to contract paint shops, adding substantial logistical costs.

Part of the door on show at the Frankfurt Motor Show was finish-painted in a batch painting process. It shows clearly that the use of prepainted sheet makes for a high-quality paint finish comparable with that produced by the conventional four-stage paint process. The paints used for the top and clear coats are baking paints as used in car production. The good forming properties of preprimed sheet have already been demonstrated in a number of fabricating tests. For assembly, joining methods such as clinching, punch riveting or adhesive bonding can be used. In the case of bonding, the adhesive has to be precisely matched to the composition of the organic coating.

ThyssenKrupp Stahl AG plays a leading role in the development of coated sheet. Around 80 percent of the company`s cold rolled strip production is metallic or organic coated. In the Dortmunder OberflächenCentrum, ThyssenKrupp Stahl also operates one of the world`s leading development centers for the coating of flat steel. Car manufacturers and suppliers are also involved in the development work, carrying out intensive tests and component trials with preprimed sheet from ThyssenKrupp Stahl.

ThyssenKrupp Steel AG
Dietmar Stamm
Tel.: +49 203 / 52 - 2 62 67
Fax: +49 203 / 52 - 2 57 07

Bernd Overmaat
Tel.: +49 203 / 52 - 4 51 85
Fax: +49 203 / 52 - 2 57 07

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