The corrosion prevention behaviour of organic coatings under the tidal zone simulation

Offshore structures in tidal zone have encountered serious corrosion problems, which have been much severe than atmospheric or aqueous corrosion. The use of organic coatings has been one of the major ways to protect these structure materials. There are many methods described in ASTM standards which can be used to evaluate the physical and chemical properties of the coatings. However, it is still desirable to develop a method that can shorten the test time and more close to the real corrosion situation under the environment used, especially for tide wave conditions. Therefore, an apparatus which could generate tide waves was developed to study the durability and protective ability of organic coatings for metal offshore materials. In this study, impermeable behaviour of epoxy, acrylic and polyurethane resin were examined under the tidal zone simulation. The results were also compared with the results obtained from traditional salt spray testing method. Impermeable behaviour of these coatings were evaluated by the time to the first observed rusts or blisters. The result shows that epoxy resin coating has better anti-corrosion ability than polyurethane resin and acrylic resin has the worst protective ability. Compared with the results obtained from salt spray test, both methods show satisfactory correlation. However, the time need for test under the tidal zone simulation is shorter than that for salt spray test.