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New types of coating systems for steel sheets by high-rate evaporation in combination with plasma processes

: Scheffel, B.; Ehlers, K.D.; Schuhmacher, B.; Floßdorf, F.-J.; Hagler, J.; Metzner, C.; Steffen, R.; Steinbeck, G.

Steel research 73 (2002), No.3, pp.114-122
ISSN: 0177-4832
Journal Article
Fraunhofer FEP ()

High-rate evaporation in combination with plasma processes is a promising approach to obtain new types of steel sheet coating with improved corrosion resistance and application properties. To estimate the potential for the application of PVD-coatings (physical vapour deposition) different coating systems for steel sheet as well as for hot-dip or elect ro-galvanized steel sheet were designed, The samples were produced on a laboratory scale using PVD processes with very high deposition rates (in the order of 1 mum s(-1)) as well as high-power plasma processes for the pre-treatment. The relationship between the composition, microstructure and properties of the coating systems, in particular concerning corrosion protection, abrasion during forming, phosphating and paint adhesion, were studied. It was found that the corrosion resistance of galvanized steel sheets can be considerably improved by vapour deposition of metal or inorganic films with a thickness of several hundred nanometers. Investigations on vapour deposition of titanium and stainless steel coatings on steel sheets, for applications in a severely corrosive environment, showed that the corrosion resistance in relation to the coating thickness can be significantly enhanced by means of plasma activation during the vapour deposition process, Finally, an outlook on possible industrial applications including an estimation of the process costs will be presented. For certain coating systems the results look promising, Consequently, these particular coating systems will be investigated in more detail by means of using a large-scale in-line deposition plant for metallic strips and sheets.