IBAD-multilayers on steel prepared by coil coating

Coil coating by using a continuous belt inside an IBAD chamber allows not only the coating of steel or polymer strips in the IBAD mode, but represents also a very flexible device for the preparation of multilayers on relatively large substrates (typically 20×30 cm2). The specific geometrical arrangement of two evaporators and a slit extraction source together with variation of the speed and direction of the moving belt provides the necessary parameters. The possible variations range from single metal layers, alloy layers over gradient layers with increasing or decreasing content of one or both phases to multilayers consisting of 2 or more sublayers. The advantages of this technique are demonstrated by the preparation of Zn/Cr-, Zn/Ti- and Zn/Mn-coatings on steel. Mainly the improvement of the corrosion behaviour was studied in comparison with conventional electrogalvanized steels and alloys prepared by normal ‘static’ alloy deposition. The samples were analyzed by SEM/EDX measurements and an industrial-like salt spray test. It could be shown that most of the multilayer coatings had much better corrosion behaviour than the electrogalvanized reference samples.