In this report, non-destructive corrosion surveys meseauring the thickness of steel sheet piles using the ultrasonic sounding thickness gauge (for underwater use) have been carried out at Nanao, Rumoi, Tachibana, Kochi, Sakaide, and Imabari Harbors and confirmation of presence of hole produced by concentration corrsion on steel sheet pile surface directly under mean low water level has been made at Wazima, Yasuda, N, Katagami, Mizushima, Hagi, Tsukumi, Aburatsu, Otaru, Urakawa, Kushiro, Sasebo and G Harbors, and the following results were obtained.
　At previous report, corrosion tendecies of steel sheet pile structures have been roughly divided into the three types, (a), (b) and (c), but as the rusult of the further corrosion suveys, it was found that new tow kinds of corrosion tendencies were occured at steel sheet pile structures at harbors besides the above corrosion tendencies (a), (b), and (c).
　Namely, concentrated corrosion was occured in the area at concave surface of steel sheet piles under residual water level while corrosion was concentrated in the area on both convex and concave surfaces of steel sheet piles directly under mean low water level, and the former was classified as corrosion tendency (b), the later as corrosion tendency (e). After all, corrosion tendecies of steel sheet pile structures in ports and harbors of Japan are classified five tendencies, (a), (b), (c), (d) and (e).