Characterization of the deep-sea environment and its effect on the behavior of trace metals released by the corrosion of structural materials

The deep-sea environment was characterized with respect to the physical, chemical and biological factors influencing the behavior of trace metals in deep-sea sediment and seawater. The characterization included a review of typical deep-sea water and sediment chemistry including trace metal concentrations, oxygen levels, reduction-oxidation potential, and concentrations of organic materials. The biological description includes typical population densities for macrofauna, meiofauna and bacteria and comparisons of trace metal concentrations in selected fish tissues. Where comparable data exist, the variations in the deep-sea environment of the Atlantic and Pacific Oceans were discussed. The effects of physical parameters such as temperature, pressure and deep-sea currents were evaluated.;Deep-sea corrosion data for various metals including representative stainless steel, carbon steel, low alloy steel and nickel chromium alloys are presented. The partitioning and fate of corrosion products released from selected alloys in the deep-sea were examined under various environmental conditions. Correlations were made with existing data on seawater corrosion of materials and with various environmental parameters. Results from both laboratory investigations simulating deep-sea conditions and from actual in-situ deep-sea experiments were correlated with long-term corrosion data obtained from shipwrecked artifacts submerged in seawater for hundreds of years to verify the methodology for extrapolating the corrosion data. The relative capability of the seawater, sediment and marine life to assimilate the trace metals released as corrosion products was evaluated. The potential for migration and transport of corrosion products in deep-sea sediment, pore water, and seawater with subsequent availability for bioaccumulation were discussed. This research assimilated existing data on pertinent physical, chemical and biological parameters affecting the corrosion of metals in the deep-sea environment to permit a concise formulation of the anticipated behavior of corrosion products released from metal submerged in seawater for extended periods of time. This provided unique insight into the physico-chemical and biological interactions affecting the corrosion of materials and similar environmental processes affecting the behavior of trace metals on the ocean floor.