Fate of corrosion products released from stainless steel in marine sediments and seawater. Part 2. Sequim Bay clayey silt

Abstract

• SUMMARYThe physicochemical speciation of corrosion products released when stainless steel is subjected to selected environmental conditions is the subject of a series of laboratory experiments at the Pacific Northwest Laboratory.This report describes laboratory experiments in which neutron-act ivated 347 stai n1 ess steel specimens were exposed to c1 ayey silt from Sequim Bay, Washington. The properties and trace metal geochemistry of the sediment and the amounts of corrosion products that were released under oxic and reduced conditions and their distribution among different chemical fractions of the sediment are discussed. Neutron-activated 347 stainless steel specimens were exposed to slurries of Sequim Bay clayey silt under aerated and non-oxygenated conditions for a period of 90 days.The redox potentials for the air-sparged and N 2 , CO 2 -sparged sediment slurries were +420 and -140 mv, respectively. In aerated sediment the estimated corrosion rate was 6.3 micrograms per year per'square centimeter of stainless steel surface area; greater than four times that amount, 28.3 micrograms per year per square centimeter, were released under anoxic conditions. Relatively labile substances constituted about half of the 60CO activity released in aerated sediment. Adsorbed 60CO soluble in DTPA and 60CO associated with sediment organic matter were the most predominant. A substantial amount (49%) of the 60CO activity was released as, or converted to, relatively inert substances requiring rigorous treatment to dissolve.The distribution of 6 0 CO released to anoxic Sequim Bay clayey silt among various extracts show that relatively labile substances constituted about 95% of the 60CO released. The largest quantity was in the organic fraction. In the absence of O 2 the association of 60 Co with the refractory (oxidic) fraction was inhibited and only ~5% of the 60CO activity was in relatively inert forms .

Fate of corrosion products released from stainless steel in marine sediments and seawater. Part 3. Calcareous ooze

“…W -Northeast Pacific red clay(Schmidt, 1982a). 2 S -Sequim Bay clayey silt(Schmidt, 1982b). 3 C -Calcareous ooze, this study.…”

“…The data on Table 11 are a summary of the distribution of 60CO activity released from neutron-activated 340 stainless steel in three different sediments: Northeast Pacifi c red cl ay (Schmi dt, 1982a), Sequim Bay cl ayey silt (Schmidt, 1982b), and calcareous ooze (this report) under aerated and non-oxygenated conditions. Severa 1 effects of different envi ronmenta 1 conditions on corrosion product distribution were determined from these experiments: * The fraction of released 60CO which was found in sediment organic matter was highest in organic-rich Sequim Bay clayey silt under either redox condition, indicating that the presence of organic matter in relatively large quantities in a sediment may be an important factor controlling corrosion product distribution.…”

“…This report is the third of a series which describes the physicochemical forms and partitioning of corrosion products released from stainless steel upon exposure to selected environmental conditions. Two previous reports discussed the amounts of corrosion products released and their physicochemical forms under oxic and anoxic conditions in North Pacific pelagic red clay (Schmidt, 1982a) and organic-rich Sequim Bay clayey silt (Schmidt, 1982b). Two major di fferences wi th respect to corrosion occurred in the two types of sediment.…”

Fate of corrosion products released from stainless steel in marine sediments and seawater. Part 4: Hatteras abyssal red clay

“…The previous reports discussed the amounts of corrosion products released and their physicochemical forms under oxic and anoxic conditions in North Pacific pelagic red clay (Schmidt, 1982a), organic-rich Sequim Bay clayey silt (Schmidt, 1982b) and calcareous ooze (Schmidt, 1982c). Major differences with respect to the release of corrosion products were observed among the di fferent types of sediment.…”