Accelerated testing; faster development of protective coatings.
Chemical Product Design and Engineering (CPD&E)
Chemical Product Design & Engineering - Poster (CPD&E - P)
Keywords: coating, adhesion, failure, corrosion, testing
The demands to protective coatings used in offshore environment are very high and modern high performance paint systems are so durable that they upon exposure to natural weathering may show little signs of deterioration. If an anticorrosive coating is intact during service life it may, for the best present products, maintain a high performance for maybe 15-20 years. The use of new technologies and paint formulations also means coatings being developed with little or no previous track record. This has resulted in more emphasis being placed on accelerated laboratory testing to evaluate coating performance. Many of these accelerated exposure tests will not, within their exposure time show the negative effects visually on intact coated surfaces. Therefore behavior of the coatings around artificially made damages i.e. scores are given significant considerations, and many prequalification tests are based amongst others on rust creep and blistering as well as detachment from scores, NORSOK M-501, ISO 20340, etc., and in the future also NACE TM 0104, 0204, 0304, 0404 etc.
The accelerated weathering methods seek to intensify the effects from the environment so that the film breakdown occurs more rapidly. However, despite the nature of these accelerated weathering methods like NORSOK M-501 rust creep on the best performing systems is typically a few mm or even less after 25 weeks of exposure. This means that in practice the value of rust creep is close to the magnitude of the experimental uncertainty. The need of faster development of efficient protective coating systems therefore calls for even stronger exposure tests. The key to develop such a tool is fundamental understanding of corrosion and the chemistry behind coating break down mechanisms.
The purpose of this paper is to describe the development of an accelerated cyclic weathering method which makes it possible to evaluate rust creep in the laboratory faster than the current international standards. Results from cyclic corrosion tests (NORSOK M501, Rev.5) on Zinc epoxy primed systems will be used as reference to the new tool.
Presented Wednesday 19, 13:30 to 15:00, in session Chemical Product Design & Engineering - Poster (CPD&E - P).
