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As part of this project, a pilot plant was installed which is capable of applying a conversion coating to black plate rings 300 mm wide using the roll coating process. With an installed coextruder and laminator, a thin plastic film can then be applied to the plates.

Paint adhesion to conversion coated plate steel was inferior to chrome plated and galvanised black plate steel. This was especially apparent after sterilisation with acid test solutions. In the packing test, the paint adhesion was reduced after 3 and 6 months and iron uptake increased considerably. In combination with a PP coating on a conversion-coated plate, a PP layer of at least 50 µm was required in order to guarantee stability in all test fluids.

With extrusion coating plates were used with a thickness ranging from 0.18 to 0.28 mm and the surfaces were chrome plated, galvanised and conversion coated. The types of plastic tested were LDPE, PP and PET.

In order to obtain adequate adhesion of the plastic layer to the tin plate, a reheating must be carried out. In order to produce a bonding that can be subject to deep drawing, a large number of extrusion technical parameters must be optimised and maintained. One of the most important criteria is a coating that is free of pinholes and pores. Storage tests with cans show that the directly extruded plastic layers must be approximately double the thickness of conventional coats of paint. So it is still questionable whether applications are economically viable.

Additional information

Authors: SAUER R, Rasselstein Hoesch GmbH, Andernach (DE)
Bibliographic Reference: EUR 20292 DE (2002), pp.14. Euro: 7.00
Availability: EUR-OP reference: KI-NA-20292-DE-S Available from EUR-OP sales agents. URL:
ISBN: ISBN: 92-894-3466-X
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