Research on Applicability of New Materials to Marine Structures in Tropical Climates: Specimens Exposed for 2 Years

New structural materials that are light and durable are anticipated to reduce the running and maintenance costs of structures exposed to harsh marine environments, such as offshore oil production facilities, thereby reducing their life-cycle cost. This study aims to investigate the applicability of new materials to marine structures, focusing on their durability. To this end, a 5-year exposure test has been conducted from 1999 on 3 types of specimens (for corrosion observation, tension testing, and joint strength testing) made of 21 selected materials (6 nonferrous metals, 8 steels, 4 composite materials, and 3 rope materials). The specimens are exposed at 3 sites: Okinotori-shima and Miyako-jima, corrosive environments with high temperature and humidity, and a thermo-hygrostatic room in a laboratory. In 2003, the fourth year of the ongoing exposure testing, the results of the observation and experiments of specimens recovered in 2002 after exposure for 3 years are subjected to analysis. The authors have already reported the detailed plan of the exposure test, initial performance of the specimens, and results of investigation on specimens exposed for 1 year. This paper reports on the results of appearance observation of specimens at Okinotori-shima and Miyako-jima carried out mostly in 2001, as well as the findings from observation and experiments on specimens exposed for 2 years at Miyako-jima. The state of corrosion at each site was grasped during the appearance observation. Observation and tension tests on jointed and unjointed specimens at Miyako-jima also revealed the state of corrosion of each material during the 2nd year of exposure.