New environmental friendly zirconium-based pretreatment systems on aluminium, steel and HDG-steel were analyzed, tested and compared to the conventional zinc phosphate pretreatment. The analyses of the surface film microstructure and compo sition were performed by Feg-SEM, TEM, XPS and FTIR. The coatings form a con tinuous film mainly consisting of zirconium oxide / hydroxide, but also fluoride and other elements that constitute the process bath are incorporated. Nodules and clus ters of nodules rich in zirconium and oxygen are distributed on top. A more detailed study of the coated aluminium substrate showed a film thickness of about 50 nm with a gradient of increasing content of aluminium closer to interface, but the film was oc casionally thicker in certain regions. The corrosion performance of painted and scribed panels of steel and HDG steel was tested in an accelerated corrosion test (ACT) for 6 weeks and in field with panels mounted on a truck for 1 year. The wet adhesion as determined by cross cut testing showed a good adherence to the sub strates. The corrosion spreading from scribe was determined, and the corrosion products were analysed by FTIR microscopy. The corrosion products determined suggested that the corrosion mechanisms were similar for the new pretreatment sys tems compared to conventional zinc phosphate. However, the corrosion and delami nation from scribe varied more for the new pretreatment systems, especially on cold rolled steel.
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