IODP Proceedings    Volume contents     Search



Visible changes in materials during incubation

Whereas most of the materials tested did not noticeably change in appearance over the course of the incubation periods and the seawater incubation solution did not alter in a visible way, some materials did show marked changes. The swellable packer polymer (Freecap) was observed to very quickly initiate swelling upon contact with solution (Fig. F2B). By the end of the incubation period (1 month), the incubation solution had acquired a noticeable bronzy hue (data not shown). Of all of the coated steel samples, the Xylan-coated coupons were the only ones that showed any rust discoloration. As evident in Figure F3, the formation of rust was quite extensive in the Xylan materials incubated at high temperatures, although rust was also evident in limited quantities in the 4°C incubated coupons.

Carbon leaching from borehole materials

In all of the experiments conducted, the rate of carbon leaching from the materials declined over time (Table T1). The carbon leaching rates revealed temperature sensitivity, with higher rates at higher temperatures (i.e., rates at 60°C were roughly an order of magnitude higher than at 4°C in several experiments). Among the baked-on resin coatings on steel coupons, the Tuboscope TK-805 product had the lowest overall carbon leaching rates (e.g., 0.4 nmol C/cm2/d after 1 month), with the other Tuboscope products leaching carbon at higher but similar rates and the Amerlock epoxy paint having the highest leaching rate over time at 60°C. The higher leaching rate of Amerlock may have been influenced by the higher comparative surface area of the Amerlock-coated coupons (Fig. F2) as compared to the Tuboscope samples (Fig. F3); however, the Xylan-coated steel coupons had a similar surface area as the Amerlock-coated coupons, and the Xylan material had a lower carbon leaching rate. The carbon leaching rates from the dried wet-paint samples of the Amerlock and Alocit 28 resins also had similar leaching rates. Among the fiberglass samples tested, the aliphatic-cured epoxy fiberglass had the highest carbon leaching rates (~100 nmol C/cm2/d after 1 month), while the carbon leaching rates from the other two fiberglass types (anhydride- and aromatic amine–cured) were lower by about an order of magnitude. The Freecap swellable packer material had some of the highest carbon leaching rates observed in this study (e.g., >1000 nmol C/cm2/d after 1 month of incubation). The standard packer material also had high carbon leaching rates in comparison to the coated steel and fiberglass materials, but the leaching rates were roughly an order of magnitude lower than those of the swellable packer material. The Eco-Sil dope, which was not used in the Expedition 327 or 336 CORKs, had the highest carbon leaching rate of all of the materials tested (>1000 nmol C/cm2/d after 1 month). The carbon leaching rates from the hydrocarbon-based Bestolife dopes were also rather high (>100 nmol C/cm2/d) even after 1 month of incubation. Interestingly, the TF-15 grease has lower carbon leaching rates than the Loctite 30561 and APT 3 sealants tested.

Nitrogen leaching from borehole materials

The nitrogen leaching rates were also higher at higher temperatures and decreased over time (Table T2). Among the baked-on resin coatings, the compounds Amerlock, Xylan, and Tuboscope TK-2 had the highest nitrogen leaching rates, which were at least an order of magnitude higher than the leaching rates of the other baked-on resins. The freshly dried Amerlock 400 and Alocit 28 resins leached more nitrogen than the baked-on coatings. The aliphatic-cured epoxy fiberglass had the highest nitrogen leaching rates of the fiberglass samples, and the aromatic amine–cured epoxy fiberglass had the lowest rates. The drill pipe/​Bestolife ZN 50 dope had lower overall nitrogen leaching rates than the drill collar/​Bestolife 60% lead-base dope, and there was no detectable nitrogen from any of the Eco-Sil incubations. The APT 3 sealant had the highest nitrogen leaching rates observed in these experiments, with rates >100 nmol/g/d after 1 month of incubation.

Fluorescence characteristics of dopes and sealants

The SYTO 9 and propidium iodide nucleic acid stains reacted with the dopes and sealants tested (Fig. F4). The SYTO 9 stain reacted with Dow Corning Compound 111 when directly applied (Fig. F4A). When this sealant was mixed with water and disrupted by bath sonication, the solution became cloudy due to the formation of small particles. These particles also reacted with SYTO 9 (Fig. F4B), and the sizes of the particles fell within the range of average prokaryotic cell sizes. These particles did not react with propidium iodide dye (data not shown). When SYTO 9 was directly applied to Loctite 30561 smeared on a glass slide, the material gained significant fluorescence (Fig. F4C). By contrast, when Loctite 30561 was mixed with water and sonicated, the high viscosity and hydrophobicity of this material did not yield prokaryote-sized fluorescent particles (Fig. F4D). Similar behaviors were also observed with the propidium iodide (data not shown). Thus, the likelihood of Loctite 30561 interfering with DNA-based cell staining techniques should be minimal. The SYTO 9 stain also reacted with the Bestolife 60% lead-base dope, as evidenced by the observation of fluorescent particles that are in the range of sizes observed for average prokaryotic cells (Fig. F4E).