ENVIRONMENTAL FATE OF CORROSION-INDUCED METAL RELEASE FROM STAINLESS STEEL

摘要

During the last decades stainless steel has seen an increased use in outdoor constructions, including architectural applications. Even though the corrosion resistance of stainless steel is well studied, reliable quantitative data on release rates of alloy constituents from stainless steel exposed outdoors are scarce or practically non-existent. Information on chemical speciation and bioavailability of released alloy constituents is also largely missing. A cross-disciplinary research project was therefore initiated to provide quantitative and accurate data on metal release rates of alloy constituents (Cr, Ni, Fe) from stainless steel grades 304 and 316 exposed to natural precipitation, and to elucidate the environmental fate of released metal through soil column investigations. Iron (release rate between 10 and 200 mg m -2 yr -1) was preferentially released compared to chromium (between 0.2 and 0.7 mg m -2 yr -1) and nickel (between 0.1 and 0.8 mg m -2 yr -1) for both grades exposed during 4 years in Stockholm, Sweden. No correlation was seen between the metal release rate and corresponding nominal alloy composition. Median concentrations of released total chromium (0.5 μg L -1) and total nickel (0.6 μg L -1) in runoff water from both stainless steel grades were far below reported ecotoxic concentrations towards aquatic organisms. Artificial runoff water, with a 10-fold increased chromium and nickel concentration, compared to natural runoff water, was used to study the interaction with soils of varying characteristics. A strong and high retention capacity was seen for both chromium and nickel. A very small amount of chromium and nickel was transported through the soil, at concentrations representative of natural leaching.