Survey of corrosion resistance of corrosion-resistant steel under marine environments, such as marine atmospheric zone, splash zone, tidal zone,submerged zone, mub zone under sea water, atmospheric zone and mud zone at land side, has been carried out by using H-shaped piles consisting of 2 kinds of ordinary steel and 12 kinds of corrosion-resistant steel at Niigata and Keihin harbours in 1965 to 1973, and the following results were obtained.
　1) It was approved that corrosion amounts of steel under marine environments were greatly influenced by corrosion environments than by kind of steel, that's to say, as a result of comparison with the range of category which was the greatest difference among the category scores calculated by component analysis, the value of corrosion environment was 2 times of that of kind of steel at Niigata harbour and 5 times at Keihin harbours.
　2) And it was found that at splash zone, corrosion amounts of P-Cu-Cr system corrosion-resistant steel were only about 50% of those of ordinary steel and even
at atmospheric zone under marine environment in which content of natrium chloride in the air were 40 to 80 mgNaCl/day/m2, most corrosion-resistant steel showed good corrosion resistance as well as at ordinary atmospheric zone. On the other hand, there were such tendencies that in sea water, corrosion amounts of corosion-resistant steel were a little lesser than those of ordinary steel, while in both mud zones at sea side and land side, corrosion amounts of corrosion-resistant were
much the same as those of ordianry steel.