Abstract
All protective coatings are thoroughly tested using accelerated laboratory tests. Accelerated testing has the advantage of providing data and results in a relatively short timeframe, and the conditions of testing are pre-defined and controlled throughout the test. However, accelerated testing also has disadvantages. Accelerated testing at e.g. tougher environmental conditions or higher temperatures may give different degradation mechanisms than at in service conditions. Field exposures can be used as a supplement to accelerated testing and can be utilized as a verification of the test setup.
In this paper, results from several atmospheric accelerated laboratory exposure tests for eight protective coating systems have been compared to results obtained from nine years of field exposure testing in a marine C5 environment.
The comparison shows poor correlation between accelerated laboratory tests and field exposures. This indicates that high performance of a coating system during accelerated laboratory testing is not necessarily predictive for high long-term performance under in-service conditions. Potentially causing premature coating failures under in service conditions.
The data presented in this study shows that although the performance in field cannot be predicted by the performance during accelerated laboratory testing, the tested coating systems comprising a Zn-rich primer, a pure epoxy second layer and a top coat shows little to none visual degradation in a severe marine environment after nine years of testing.
