Abstract
Topcoat flaking has been, and still is, considered to be a significant problem on both onshore and offshore structures in the Norwegian sector. Polysiloxanes, the predominant topcoat in the Norwegian market during the last few years, may seem to be particularly vulnerable to this degradation mechanism, but also other generic type topcoats exhibit a similar behavior. Qualification testing according to established standards, e.g. Norsok M-501, does not seem to be able to reveal the potential problem and there is a need for a better understanding of the failure mechanism(s). Such knowledge is a necessity in order both to implement corrective measures to prevent this problem in the future, and to improve the qualification test methodology.
A finite element method (FEM) approach has been suggested in order to determine the importance of different coating properties, e.g. adhesion, internal stress, stress-strain behavior, elongation before rupture etc. This is a three-step process: 1) Determination of internal stress and mechanical properties of single coatings, 2) Determination of interfacial factors and any inter-coat effects (e.g. adhesion), and 3) Building and testing the model. Both steps 1) and 2) include an evaluation of the quality of the established data. This paper summarizes the first part of the study on topcoat flaking mechanisms.
