AVS 46th International Symposium
    Applied Surface Science Division Thursday Sessions
       Session AS-ThM

Paper AS-ThM6
Failure Mechanisms of Adhesively Bonded Hot Dipped Galvanised Steel Studied by Small Area XPS

Thursday, October 28, 1999, 10:00 am, Room 6A

Session: Real World Surface Analysis
Presenter: R.G. White, VG Scientific, UK
Authors: R.G. White, VG Scientific, UK
M.F. Fitzpatrick, University of Surrey, UK
J.F. Watts, University of Surrey, UK
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One of the most important requirements of an adhesive joint is the retention of strength for an acceptable time on exposure to a hostile environment. Durability is recognized as one of the most significant problems in the adhesive bonding in industry. In a previous paper, small area XPS established that electrochemistry was responsible for initial bond degradation in a phosphated hot dipped galvanised steel (HDGS) lap joint.@footnote 1@ This paper reports a surface analysis investigation of the failure mechanism of adhesively bonded hot dipped galvanized steel that has been exposed to a hostile environment. The failed lap shear joints show areas of apparent interfacial failure, however, these regions are limited to thin strips at the end of the overlap. These "initiation zones" seem to be a result of environmental exposure and appear to act as initiation sites for crack propagation on mechanical testing, acting as "notch like" features. The study of these areas of the failed surface using small area XPS (15 micron resolution) is reported in this paper, with a view to establishing the role of electrochemical activity at the crevice tip and its role in the subsequent joint failure. Acknowledgement : The authors wish to thank British Steel Strip Products and Welsh Technology Centre for the provision of a Research studentship (MFF) and for permission to publish this paper. @FootnoteText@ @footnote 1@J.F.Watts and M.F.Fitzpatrick Surf. Interf. Anal. in press.