Stability diagrams for Ca, Mg, CO2, P, Si, Fe and F in seawater have been estimated to understand the dissolution behavior of steelmakingslag constituents into seawater as nutrition for phytoplankton propagation. Dissolution behavior of each element from crystal phase present in steelmaking slags into seawater has been discussed based on the stability diagram. The presence of 4CaO·P22O5phase in steelmaking slag is preferred for effective phosphorus dissolution into seawater. Increase of pH value by Ca elution and buffering action of Mg in seawater against it have been clearly explained by using stability diagram. Elution behavior of environmentally restricted elements from steelmaking slag into seawater was also estimated. It was confirmed that stability diagram was a powerful tool to understand dissolution behavior of steelmaking slag.
