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In applying an analytical method to the analysis of an organic coatingmetal substrate system that has failed, either in service or as the result of some form of accelerated test, there are certain criteria which must be met. These include the following. Firstly, it should be possible to define accurately the locus of failure (preferably at an atomistic level), i.e., did cohesive or adhesive failure occur in the region of the metal to polymer junction? Secondly, as failure often occurs as the result of exposure to an aggressive environment [e.g., water or salt (NaCI) solution], it is desirable to monitor the concentration of these species at the failed interface. Thirdly, the action of such aggressive media may bring about chemical changes only a few atom layers deep at the interface, which lead to adhesion loss. Consequently any analysis technique used must be very surface specific. In addition there is the rather more obvious requirement that polymeric materials can be analysed without sample degradation, desorption of labile species, or electrostatic charging; this effectively precludes the use of electron, and most ion probe, methods. The analytical technique best suited to such investigations is X-ray photoelectron spectroscopy (XPS). In this paper the use of XPS will be illustrated by examples of recent work on the adhesion and subsequent failure of two markedly different organic coatings on mild steel.

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