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

New zinc-magnesium surface improves corrosion protection

Dortmunder OberflächenCentrum, the Dortmund, Germany-based surface engineering center, has developed a new alloy coating based on electrogalvanized steel sheet which offers significantly improved anti-corrosion properties. Using this new alloy, corrosion protection at least equivalent to that of conventional galvanized sheet is achieved with only half the coating thickness. Maintaining the standard coating thickness significantly boosts anti-corrosion performance.

To manufacture this new coating, a very thin additional layer of magnesium is applied to electrogalvanized sheet by physical vapor deposition. For this, the magnesium is heated to 600°C in a crucible and the resulting magnesium vapor deposited on the galvanized strip via nozzles. Subsequent heat treatment causes the zinc and magnesium to interdiffuse, resulting in a zinc-magnesium alloy coating.

The magnesium vapor has to be deposited on the galvanized strip under vacuum. The pilot line used at Dortmunder OberflächenCentrum to test and prototype new coatings has a corresponding vacuum section which allows continuous production of the new coating. The thickness of the zinc-magnesium layer is controlled by the amount of magnesium vapor used.

The new finish provides particular advantages when processing for automotive construction. For example, the reduced coating thickness makes laser welding easier than with conventional galvanized steel. If, on the other hand, the standard coating thickness is retained, the enhanced anti-corrosion properties of the material allow a significant reduction in secondary protection measures such as cavity or seam sealing.

With continuous trial production on the pilot line successfully completed, the prototype product ZE-Mg is now being further developed with a view to commercial application.

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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