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The goal of this project was to develop new techniques for the study of surface treatment reactions during the reaction. Surface treatment reactions involve the simultaneous dissolution of substrate metal and film growth and therefore a number of complementary techniques were required to fully characterise the reaction. ICP spectroelectrochemistry gives a direct measure of the metal and alloy dissolution rate by monitoring the elemental composition of the electrolyte. Quartz crystal gravimetry measures the mass changes of the sample that reflect the difference between mass loss by dissolution and mass gain by film formation. When coupled with the ICP technique, the rate of film formation can be determined. In situ Raman yields information on solid state changes in the surface film. In addition, environmental scanning electron microscopy and atomic force microscopy have been used to observe nucleation and growth of phosphate films. These techniques were used to investigate the role of secondary metal ions (Mn+2, Ni+2, Fe+2) in the phosphate layer on the chemical stability of the phosphate layer, the role of accelerators in the phosphating reaction and the alkaline resistance of zinc alloy coatings during alkaline degreasing. As for the chemical stability of the phosphate layer, it was found that secondary elements reduce the rate of alkaline leaching directly in proportion to their concentration in the layer. Accelerators in the phosphating bath were found to have important stabilising properties probably by suppressing hydrogen evolution and, in phosphate solution, they lead to a passivation of the zinc surface by film formation.

Additional information

Authors: OGLE K, Arcelor (IRSID), Maizières-lès-Metz (FR);TOMANDL A, Voest-Alpine Stahl GmbH, Linz (AT);WOLPERS M, Henkel, Wien (AT);VALETTE M, Arcelor Atlantique et Lorraine, Montataire (FR)
Bibliographic Reference: EUR 21635 EN (2005), 149 pp. Euro: 25
Availability: Katalogue Number: KI-NA-21635-EN-S The paper version can be ordered online and the PDF version downloaded at:
ISBN: ISBN: 92-894-9517-0
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