LONG-TERM EXPOSURE TEST AT HAZAKI OCEANOGRAPHICAL RESEARCH STATION

Classification of corrosion environments

Even for the same steel pipe pile, the corrosion environment will vary depending on the height. These corrosion environments are classified into the marine atmospheric zone, splash zone, tidal zone and submerged zone.

Tidal zone: NAS 254N under marine organisms (no corrosion)

This is a zone that experiences repeated immersion and exposure to seawater due to the ebb and flow of the tides. Corrosion can easily occur due to marine organisms adhering to the surface (crevice corrosion).

Before and after removal of marine organisms

Splash zone: NAS 185N (no corrosion)

This is a zone that is continually exposed to the atmosphere and is splashed with waves. Corrosion (pitting corrosion, crevice corrosion) can easily occur due to the concentration of salt (Cl-) from the evaporation of seawater attached to the pile, and from temperature risings on the surface of the steel due to sunlight.

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