Corrosion survey of No.1 lock gate at Amagasaki Harbor has been carried out, and the following results were obtained.
　There was such corrosion tendency that concentrated corrosion was generated on projecting portion of lock gate, i.e. edge of beam and so on, directly under M.L.W.L. as well as on flat portion of convex steel sheet pile, and their corrosion rates were 1.0 mm/yr or more. In contrast to this, corrosion rates of lock gate in the direction of thickness were 0.1 mm/yr or less even directly under M.L.W.L. and also, the corrosion tendency mentioned above could be seen on screen, one of the facilities attached to lock gate.
　As the result, it was ascertained that it was necessary, in order to grasp actual state of corrosion of steel structure, to carry out corrosion survey concerning the whole of that.