The south part of Japan is located in the subtropics. Therefore, steel corrosion in concrete in this region easily tends to initiate and progress due to chloride ion ingress into concrete from the seawater. Under this environment, in order to enhance the durability of reinforced concrete structures in which sufficient concrete cover depth can not be secured due to some restrictions, it is very effective to apply adequate surface coating materials on the concrete surface at early age of exposure. To study the durability of concrete with various surface coating materials under marine environment in the subtropics, exposure test was carried out in the south part of Japan. Various tests such as bond strength of surface coating materials, chloride ion content in concrete and corrosion evaluation of steel bar in concrete were carried out after 15 years of exposure. These results indicate that these surface coating materials are very effective in enhancing the durability of concrete under marine environment. This protection against chloride attack was well maintained for 15 years of exposure to a marine environment.