99. Corrosion Properties of PVD-Coated Magnesium Die Cast Alloy AZ91D – Part II: Contact Corrosion Properties of Differently PVD Treated Magnesium Die Cast Alloy AZ91

  1. Prof. Dr. K. U. Kainer
  1. H. Hoche1,
  2. C. Blawert2,
  3. E. Broszeit1 and
  4. C. Berger1

Published Online: 22 APR 2005

DOI: 10.1002/3527603565.ch99

Magnesium: Proceedings of the 6th International Conference Magnesium Alloys and Their Applications

Magnesium: Proceedings of the 6th International Conference Magnesium Alloys and Their Applications

How to Cite

Hoche, H., Blawert, C., Broszeit, E. and Berger, C. (2003) Corrosion Properties of PVD-Coated Magnesium Die Cast Alloy AZ91D – Part II: Contact Corrosion Properties of Differently PVD Treated Magnesium Die Cast Alloy AZ91, in Magnesium: Proceedings of the 6th International Conference Magnesium Alloys and Their Applications (ed K. U. Kainer), Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, FRG. doi: 10.1002/3527603565.ch99

Editor Information

  1. GKSS-Forschungszentrum, Institut für Werkstoffforschung, Max-Planck-Straße, 21502 Geesthacht, Germany

Author Information

  1. 1

    Staatliche Materialprüfungsanstalt und Fachgebiet und Institut für Werkstoffkunde an der Technischen Universität Darmstadt, Darmstadt, Germany

  2. 2

    GKSS Forschungszentrum Geesthacht GmbH, Geesthacht, Germany

Publication History

  1. Published Online: 22 APR 2005
  2. Published Print: 27 NOV 2003

ISBN Information

Print ISBN: 9783527309757

Online ISBN: 9783527603565

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Keywords:

  • contact corrosion properties;
  • PVD-coated magnesium die cast alloy AZ91D

Summary

The publication is divided into two parts. Part described the general coating and corrosion properties as well as the electrochemical properties of the following coating systems:

  • 9 µm CrN hard coating [1]

  • 3 µm TiN hard coating

  • 0.5 µm plasma anodisation (PA) layer & 3 μm Al2O3 coating [2]

Summarizing the results of part I, the PA+ Al2O3 coating system showed outstanding corrosion behaviour in comparison to the CrN and the TiN coatings. In the salt spray test the PA + Al2O3 specimens at least came off as good as a commercially available plasma chemical anodisation with sealed porosity. The current densities vs. potential curves obtained in the electrochemical measurements allow an additional classification of the corrosion behaviour of PVD coated AZ91 using the cathodic brunch of the polarisation curve to calculate the corrosion rate. However further information about the corrosion mechanisms involved can be obtained if the surface and cross section of corroded specimens are studied. TiN and CrN reveal debonding of more or less the whole coating at the interface, while the interface remains intact for the PA + Al2O3 coating.

Part II describes the results of a novel immersion technique to determine the time dependent corrosion behaviour of coated magnesium alloys [3]. Furthermore contact corrosion properties of the above mentioned coatings according to DIN 50919 are presented. The specimens were tested in an 3% NaCl solution against the aluminium alloys AlMgSi 0,5 and AlSi9Cu3 and against a roller bearing steel 100 Cr 6. The tested specimens were investigated by means of optical microscopy, SEM and EDX.