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POSCO Uses Steel Slag to Create Sea Forests and Save the Marine Ecosystem

POSCO announced on June 3 that it has installed artificial reefs made of slag off the coast of Ulleung Island under a sea forest cultivation program launched to mark National Ocean Day (May 31).

The installed Tritons have been acknowledged as artificial reefs by the Ministry of Oceans and Fisheries. The 100 Tritons were placed on the edge of the sea forest to facilitate the growth of marine algae while 750 Triton blocks were stacked up in the center, serving as a habitat and breeding ground for fish.

Steel slag, the main material of Tritons, has high mineral content such as calcium and iron, which are useful for marine ecosystems, than general aggregates. Not only can the Triton facilitate the growth of marine algae, but it can also promote photosynthesis, thus restoring the marine ecosystem and diversifying coastal organisms as well. Also, the Triton reef can withstand typhoons and tsunamis due to its high gravity and strength and is highly resistant to seawater corrosion.

POSCO plans to develop sustainable sea fertilizer and a new type of artificial reef using steel slag. These developments are expected to contribute to restoring the marine ecosystem and also help improve the income of local fishermen.


Marine corrosion of steel is strongly associated with the vital activity of bacteria. The long-term corrosion process develops differently than the one of earlier stages. On the early stage, corrosion is controlled by an inflow of dissolved oxygen, while the activity of anaerobic bacteria under corrosion products layer controls the corrosion in later stages. Usually, hydraulic structures with metal elements have lifetimes much longer than 2-3 years; consequently, the vital activity of anaerobic bacteria determines the long-term corrosion prediction.

Dimitrios S. Sophianopoulos, Vasiliki S. Pantazi and Maria Ntina made a study on the marine corrosion of steel with aerobic and anaerobic biofilms.

In this paper, a diffusional model of marine corrosion wear for steel structures is developed and presented in this work, based on the assumption that long-term corrosion depends on both aerobic and anaerobic bacterial activity, which is connected with nutrient changes. This activity of bacteria biofilms is quantitatively evaluated and verified, based on observed data of hydraulic structures of Far East of Russia.

It is shown that any short-term increases of nutrients and anthropological pollutant concentrations may significantly accelerate the corrosion . Also, the role of anaerobic biofilms accelerating the corrosion of immersed steel structures is underestimated.

Read the full paper at Journal of Architecture and Design Review: