Dr. Bernhard Wessling
Ormecon Chemie GmbH & Co. KG, Ammersbek
(a subsidiary of Zipperling Kessler & Co.)
This test can be performed in two ways, (a) by coating half of a panel with CORRPASSIVTM primer, the other half with a conventional epoxy primer, then applying a top coat (e.g. 2-C EP) on both primers, or (b) by coating a panel completely with the coating system to be tested.
The coating is then injured with scratches 1 mm wide and 50 mm long, down to the metal. The panels are immersed in 10% salt containing water. After 1 night and after 100 and 300 hours, the panels are checked with respect to rust formation in the scratch: only those systems will be accepted to become commercial CORRPASSIVTM products, where no rust will be formed within the open scratch during this time (see Fig. 4). Conventional systems, also the very good ones, will develop rust in the open scratch, because the area there is not protected. They also develop rust under the coating, propagating at various velocities (cf. 4.3).
The protection provided by CORRPASSIVTM, the ennobling, however is a far-reaching effect because of its metallic nature. We are assuming furthermore, that it is not only the ennobling which provides protection for open scratches of this size, but also the passivation by Fe2O3 formation: this oxide can be found up to about 400 µm away from the coating edge as seen by XPS[35].
This protection can be effective more than 1 mm away from a coating edge, which makes anti-corrosion systems based on our Organic Metal a powerful edge corrosion protection technology. We even have sometimes found much bigger areas being protected even after removal of the coatings[36].
