M. Dornbusch, T. Biehler, M. Conrad, A. Greiwe, D. Momper, L. Schmidt, M. Wiedow
University of Applied Sciences, Adlerstraße 32, 47798 Krefeld, Germany
Received 12.06.2015, accepted 29.02.2016, published 14.04.2016
JUnQ, 6, 2, 1–7, 2016
The formation of a conversion layer for corrosion protection based on phytic acid (PA) solutions is described several times in the literature. The promising results induced us to verify the performance of PA based conversion layers as pre-treatment for organic coatings. The spectroscopic and optical analysis with infrared spectroscopy, atomic force microscopy, and scanning electron microscopy of the generated layer strengthened the hypothesis of a corrosion protective layer. Furthermore, the electrochemical analysis with cyclic voltammetry supported it but the results of the electrochemical impedance spectroscopy provided a first hint of an instable layer. Unfortunately, all kinds of tested conversion layers based on PA with and without a combination with molybdate increased the delamination of an applied coating and accelerated the corrosion process in the salt spray test. Therefore, all investigated PA based conversion layers are not suitable as pre-treatments for organic coatings.
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