港湾における鋼材腐食の研究 (第2報)

港湾鋼構造物の腐食調査法および広畑港, 大阪港における鋼矢板腐食速度

抄録

The corrosion survey method for steel structures at harbors has not been yet standardized and the non-destructive survey using Sakata-type thickness meter has been made in this country.
Results by the non-destructive method, however, were not compared with those by destructive method carried out in situ. It is shown in the previous paper that the corrosion rate of the steel pile under H. W. L. is fairy smaller than the values estimated formerly by the non-destructive survey.
Then, to determine the corrosion rate of steel structures, we carried out at Hirohata and Osaka harbors both the non-destructive survey with a new ultrasonic thickness meter (resonance type for underwater use) and the destructive survey using steel pieces cut from quay walls.
Results obtained are summerized as follows:
(1) The thickness measurement with the ultrasonic thickness meter was nearly satisfactory. However, since the number of locations measurable with the thickness meter was from 60 to 90per cent of the total determination sites, it is desirable to make a survey with both non-destructive and destructive methods.
(2) Corrosion rate of steel piles formerly estimated by the non-destructive survey is at least several times as much as the one obtained in this survey.
(3) Corrosion rates of steel piles were 0.01-0.03mm/yr above H. W. L., 0.10-0.12mm/yr at H. W. L. and 0-0.05mm/yr between H. W. L. and mud line.