Takuya TAKAHASHI

A Study of the influence of marine salts on Weathering Steel Bridges in Niigata

Masatsugu NAGAI and Eiji IWASAKI

The Weathering Steel with its strange properties of rust is resistant to atmospheric corrosion. A rust layer produced on the Weathering Steel gets compact and stable through a wet-and-dry action just like a paint film. This is very economical and superior from the viewpoint of saving materials and energy.
In Niigata, the Weathering Steel has not been used at the location where the distance from the seashore is less than 20 kilometers, except that marine salts density is less than 0.05 mdd. However, there are a lot of Weathering Steel Bridges in the area within 20 kilometers from seashore and the state of rust has not been observed.
Therefore, in this study the influence of marine salts on Weathering Steel Bridges is observed by measurement of marine salts density, surface salts density on the steel and thickness of rust to use of plan for construction of bridge in the future and to reference at the time of maintenance.

The following results are obtained by the observation:
1. Marine salts come flying mostly during winter and adhere to a bridge. However they does not accumulate.
2. On a part where influence washed away by rain and dew condensation is little, there is the correlativity between marine and surface salts density.
3. The state of rust is good judging from thickness of rust of the entire bridge even if distance from seashore is less than 20 kilometers.
4. The annual thickness of rust has relevant to marine salt density and the distance from the seashore.