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  • Influence of segregated tramp elements on the surface of cold-rolled steel sheet with regard to the metallic coating processes and application properties


Final report on Contract no. 7210-PR/064, 1 July 1997 to 31 December 2000.

Industrial melts with high and low levels of tramp elements were produced by addition of selected scrap qualities. Based on these melts, and samples from lab melts, the surface segregation of the tramp elements at different production steps was analysed by XPS, SNMS, and GDOES. The amount of surface segregation is mainly determined by the bulk analysis of the steel sheet and can only be slightly influenced by other production parameters.

The starting point of the electro-coating process can obviously be affected by the presence of tramp elements, reducing the activity of the surface for the nucleation process. Nevertheless, for a coating thickness of 7.5 µm the differences vanish. The orientation of the Zn crystals after electro-galvanising shows a good correlation with the texture of the surface grains of the steel determined by EBSD.

During hot-dip galvanising a Cu content of 0.14 % can lead to a slightly pronounced formation of intermetallic Fe-Zn phases. However, no degradation of coating adhesion has been observed. Generally, effects of different tramp element levels on the hot-dip galvanising behaviour were hardly detectable. When a tri-cation phosphating bath is used, coverage of the steel surface is hardly influenced by tramp elements, though crystal size and coating weight can differ considerably. The evaluation of the corrosion behaviour (ZnMn-phosphating, powder coating) revealed that samples with a high level of tramp elements show a better corrosion resistance, which could be correlated to the Cu content.

Additional information

Authors: KOLL T, Salzgitter, Salzgitter (DE);SCHUHMACHER B, TKS, Dortmund (DE);SCHMITZ B, CRM, Liège (BE);RAUCHER R, VASL, Linz (AT);GERDENITSCH J, VASL, Linz (AT)
Bibliographic Reference: EUR 20336 EN (2002), pp.119. Euro: 17.50
Availability: EUR-OP reference: KI-NA-20336-EN-S Available from EUR-OP sales agents. URL:
ISBN: ISBN: 92-894-3666-2
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