To make clear the long term effects and durability of various Kind of corrosion prevention systems for port and harbour steel facilities, a series of large scale field exposure tests have been carried out. In this interim report, handling and execution procedure, specification and exposure results of three or four years are presented.
　Major findings are as follows:
1)In the case of underwater lining, deterioration due to rust and cracking is observed at the cutting marks of scaffolding on the steel surface. It may be from insufficient treatment of steel surface.
2)In some cases using protective cover, a fixing belt and protective covers are deteriorated. Fixing belts and protective covers must have sufficient strength against external forces such as wave and drift.
3)Regarding to the systems of protective painting, rust stain at cutting mark are observed in some cases. Sufficient amount of painting thickness is necessary at projection points on steel surface.