Performance of marine and offshore paint systems: correlation of accelerated corrosion tests and field exposure on operating ships

摘要

Corrosion resistance is an important property requirement for marine paint systemsused in naval industry such as for ship’s topsides and superstructures, which obligestesting the coating performance in order to make a durable selection of the paintsystems. This can be achieved by performing laboratory accelerated corrosion testsrecommended for C5M corrosivity class (in particular the standard neutral salt spraytest ISO 9227 or the cyclic corrosion test ISO 20340-Annex A) which give results in arather short delay (up to 6 months) compared to field exposures in marineatmospheres (several years). It is however well-known that these tests may not befully representative of real ship environmental conditions.The aims of the present study were thus to compare and estimate the correlation ofvarious accelerated corrosion tests including standardized tests (ISO 9227,ISO 20340, ISO 16701) and newly developed test conditions to field exposures onworldwide operating ships (container carrier vessel and oceanographic ship) and onconventional static marine atmospheric sites (C5M). Fifteen different marine paintsystems commonly used for offshore and naval application were selected for thestudy. From the results, the exposure conditions on the container vessel were themost aggressive ones compared to static exposures after two years. The bestcorrelation to such field exposure was observed using the cyclic test ISO 16701 witha deviation inferior to 25%, an acceleration factor of 4 and comparable corrosionaspect. If all testing conditions involving NaCl 5wt% (including ISO 20340) showed asuperior acceleration factor (e.g. about 12), a larger deviation (50%) was howeverfound indicating that these tests didn’t accelerate the corrosion degradation of thepaint systems similarly to field exposures. In addition, conditions for an optimizationof ISO 20340 annex A test were found.