TN - | 263 Technical Note N-1263 EFFECT OF BOTTOM SEDIMENT CONTAINING HYDROGEN SULFIDE ON MATERIALS - PART I By James S. Muraoka March 1973 Approved for public release; distribution unlimited NAVAL CIVIL ENGINEERING LABORATORY Port Hueneme, California 93043 mie UNI Weer EFFECT OF BOTTOM SEDIMENT CONTAINING HYDROGEN SULFIDE ON MATERIALS - PART I Technical Note N-1263 YF 54.543.007-01-.001 by James S. Muraoka ABSTRACT Plastic, synthetic ropes, natural fiber ropes, electrical cable insulations, and a wood panel were partially exposed in the black, bottom sediment of Port Hueneme Harbor to determine the effect of hydrogen sulfide on materials. After one year of exposure, the materials were recovered and examined for fouling and biodeterioration. In addition, hardness and moisture absorption tests were conducted on the plastic panels while tensile strength tests were conducted on rope specimens. Significant changes in hardness and moisture absorption were registered by nylon and phenolic laminate plastics. Decrease in tensile strength was experienced by all of the synthetic rope specimens. The natural rope specimens were totally destroyed by marine organisms. The wood panel was riddled by marine borers. ii INTRODUCTION An anaerobic environment devoid of oxygen and where marine sulfate-reducing bacteria flourish and produce hydrogen sulfide is found in many parts of the world's oceans. These areas are usually found in places where circulation of oxygenated seawater is restricted or reduced such as in harbors and bays (especially in bottom mud) and in basins (bottom waters of the Black Sea). In an anaerobic environ-= ment, the sulfate-reducing bacteria utilize sulfates and sulfites in the absence of oxygen during their metabolic process leading to the formation of hydrogen sulfide (rotten egg smell). The anaerobic corrosion of metals exposed in such an environment is widespread and destructive. For example, it is reported that extensive corrosion and deterioration is experienced by pipes, pumps, storage tanks, steel pilings in harbors, mooring chains of buoys, ship hulls, and painted surfaces of metals in such an environment. ?~? To obtain additional knowledge about what will happen to materials exposed in bottom sediments containing hydrogen sulfide, materials other than metals were exposed in the bottom mud. Reported herein are the test results obtained on various plastic materials, synthetic and natural fiber ropes, electrical cable insulating materials, and a Douglas fir panel which had been exposed in the bottom sediment of Port Hueneme Harbor for a period of one year. MATERIALS AND METHOD For the long-term exposure tests in the bottom sediments contain- ing hydrogen sulfide, 6x12 inch plastic specimens of varied thicknesses were placed in a rack as shown in Figure 1. The specimens were held in place by four molded, grooved polyethylene insulators and were separated from each other by one inch. The center divider and end plates were titanium alloy 75-A. The rods through the insulators were nickel-copper alloy 400 fastened with nuts and washers of the same composition. Polyvinyl chloride (PVC) washers were used between the metal washers and the end plates. Prior to placing the 6 x 12 inch plastic panels in the titanium rack, each specimen (listed in Table 1) was weighed and then tested for hardness with a Durometer Type D or Type A-2 in a temperature and humidity controlled room (75°F, 20%RH). Rope specimens (nylon, polypropylene, polyester, manila, and cotton) with eye-splices were placed around the titanium rack in such a way that the center section of the ropes would be embedded in the mud. The eye-splices were placed in each rope specimen WOU UNA A 0 0301 OO40e so that tensile strength tests can be conducted on the recovered ropes. Six inch long electrical cables covered with different insulating materials (butyl rubber, neoprene rubber, natural rubber, PVC, poly- ethylene, and TFE) were also tested by securing these to a phenolic laminated plastic plate (Figure 2). For sign of any deterioration, only visual examinations were conducted under a sterescopic microscope on the recovered cable specimens. A Douglas fir panel was also attached to the rack to determine if marine wood boring animals are present at the sediment-seawater interface. Two titanium test racks (one rack to be exposed for one year and the second rack for a period of two years) with materials were prepared and placed in the black bottom sediment present in Port Hueneme Harbor by scuba divers (Figure 3). A shovel was used by the divers to bury the racks in the sediment because it contained a mixture of large and small rocks and debris, making it difficult to shove the racks deeply into the mud. A third rack with replicate test specimens was exposed near the surface of the water from an NCEL corrosion testing dock located inside the Port Hueneme Harbor. The rack was suspended with a synthetic rope about three feet below mean low tide from the dock. Plans are to expose this rack near the surface for a period of two years so that the effects of fouling, biodeterioration, and other changes which may occur to the test panels can be compared to those replicate panels exposed in the bottom sedi- ments. RESULTS AND DISCUSSION Bottom Rack The titanium rack with materials which has been exposed in the bottom sediment for a period of one year was recovered by divers during the month of September 1972 (Figure 4). The depth into which the materials were buried in the sediment can be determined by the end plate of the titanium rack (Figure 5). There was light fouling growth attached to the recovered materials. The sessile organisms found attached to the materials were composed mostly of encrusting bryozoa (several species), calcareous tubeworms, and rock oysters. These fouling organisms are not adversely affected by living ina seawater environment containing hydrogen sulfide and low dissolved oxygen concentration. After the plastic panels (6 x 12 inch) were cleaned of marine growth, hardness and moisture absorption tests were conducted. The results of these tests are presented in Table l. The hardness test was conducted over two different sections of the surface of the plastic panels - the section which was buried in the mud and the section which was exposed to seawater above the mudline. The two sections would be distinguished by the discoloration present in the plastic panel. For example, the section of a PVC panel (grey) buried in the sediment had turned to black. The hydrogen sulfide in the sediment had reacted with either the tin or the lead present in the PVC plastic panel to form tin or lead sulfide which is black. In another marine exposure test a vinyl paint (orange) containing lead had changed to black when exposed in an anaerobic nu onmene contain- ing hydrogen sulfide in the deep-ocean environment. There was no significant difference in hardness between the two sections. It should be noted, however, that polyethylene and nylon showed a slight increase in hardness where it was exposed in seawater as compared to the section buried in the sediment. There were some differences in hardness between the unexposed (dry) and the exposed (wet) panels. For example, polyethylene, polypropylene, vinyl (pp), PVC, polystyrene, and TFE increased in hardness after being exposed in seawater. On the other hand, phenolic laminate and nylon panels decreased in hardness. The hardness of vinyl (pm) polycarbonate, acrylic, and polyurethane panels remained about the same before and after exposure in the sea. Most of the plastic materials did not absorb significant amounts of moisture during the one year exposure in the harbor. The exceptions to this were phenolic laminate and nylon panels which absorbed signif- icant amounts of moisture during this period. The recovered rope specimens (nylon, polyester, polypropylene, manila, and cotton) were covered with a layer of fine silt and some encrusting bryozoans. The fibers of manila and cotton ropes were deteriorated so severely by microorganisms that the fibers could easily be torn apart by one's fingers (Figure 6 and7). The results of a tensile strength test conducted on the recovered synthetic ropes are presented in Table 2. The tensile strength of polyester, poly- propylene, and nylon ropes decreased by 6.3, 9.5, and 19.7 percent, respectively. Data on tensile strength of manila and cotton ropes were not obtained since these had been severely deteriorated by biological activity. It is of interest to note that, although the tensile strength of polypropylene ropes had decreased when exposed in the bottom sediment, it had increased when such rope specimens were exposed in the deep-ocean environment (6000-ft depth). Visual examination of the electrical cable insulations (butyl rubber, neoprene rubber, natural rubber, PVC, polyethylene, and TFE) conducted under a stereoscopic microscope showed that the surface of a natural rubber insulating material had deteriorated badly, probably due to effects of hydrogen sulfide and microorganisms (surface crack- ing). The other materials were in good condition. Fouling organisms which were found on the various insulating materials included en- crusting and branching bryozoans, hydroids, calcareous tubeworms, and small barnacles (Figure 8). The 1/4 x 4 x 12 inch Douglas fir panel which was exposed immediately above the bottom sediment was riddled by Bankia and Teredo (molluscan borers) and also by Limnoria quadripunctata and Chelura (crustacean borers) as shown in Figure 9. Surface Rack The replicate test specimens in a titanium rack exposed at the surface of the water in Port Hueneme Harbor was covered with a moderately dense growth of fouling - considerably more than the rack which had been exposed in bottom sediments. Large mussels, barnacles, encrusting and branching bryozoans, tubeworms and kelps were the major fouling growths found attached to the plastic panels and rope specimens (Figure 10). Compared to the severely deteri- orated condition of the cotton and manila ropes exposed at the bottom, the cotton and manila rope specimens exposed at the surface were in relatively good condition. As soon as the visual inspection was completed, the rack with the test specimens was immediately submerged in the harbor water for continued testing. CONCLUSIONS Biodeterioration of materials such as cotton and manila ropes (natural fibers), and wood placed exposed on the bottom sediment were severe and rapid due to the activity of microorganisms and wood borers. The synthetic fiber ropes (nylon, polypropylene, and polyester) were not affected by marine organisms but were affected by seawater in an anaerobic environment resulting in decreased tensile strength. A natural rubber electrical insulating material exposed in the bottom sediment experienced severe surface cracking, probably due to the effect of both hydrogen sulfide and microorganisms. Other insulating materials such as neoprene rubber, PVC, polyethylene, and TFE were not affected. Except for the 6 x 12 inch phenolic laminate and nylon panels, the majority of the 6 x 12 inch plastic panels were not affected significantly by the seawater - hydrogen sulfide environment found in the bottom sediments of Port Hueneme Harbor. The principal fouling organisms found attached to the test materials exposed at the bottom were encrusting bryozoans (several species), calcareous tubeworms and rock oysters. FUTURE PLANS The second titanium rack with replicate test panels as above, is undergoing continued exposure testing in the bottom sediment at the same location. It will be recovered after two years of exposure and the materials will be examined and evaluated for fouling attach- ment, biodeterioration, and other changes which may occur during this period. The materials exposed at the surface of the water in Port Hueneme Harbor will also be examined and evaluated at the same time for comparison purposes. 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Result of Tensile Strength Test on Ropes (lbs) Diam. Be fore 1.2 Percent | (inch) | Exposure ? After Exposure ’ Change Polyester 1/4 1533 1437, 6.3 er Polypropylene| 1/4 1137 1029 9.5 decrease Nylon 1/4 1514 1215 19.7 decrease epee 1/4 701 Biodegradated Cotton 2 1646 Biodegradated tL _ 1. Average of 2 ropes 2. Tensile strength applied at 3 inch per minute 3. Type M, Class 2. 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Robert L. Starkey, '"Sulfate-Reducing Bacteria - Physiology and Practical Significance," University of Maryland, 1961. A. W. Baumgartner, "Sulfate-Reducing Bacteria; Their Role in Corrosion and Well Plugging," Producers Monthly, July 1962. Richard D. Pomeroy, "The Role of Bacteria in Corrosion," Proceedings of First Western States Corrosion Seminar, National Association of Corrosion Engineers, 1967, pp. 233-236. Naval Civil Engineering Laboratory. Technical Report R-428, "Deep-Ocean Biodeterioration of Materials - Part III. Three Years at 5,300 Feet," by J. S. Muraoka, February 1966. James S. Muraoka, 'Deep-Ocean Biodeterioration of Materials," Ocean Industry, February, March 1971. 18 No. Activities 182 DISTRIBUTION LIST Total Copies 12 10 182 Defense Documentation Center Naval Facilities Engineering Command NAVFAC Engineering Field Divisions Public Works Centers Public Works Centers RDT&E Liaison Officers at NAVFAC Engineering Field Divisions and Construction Battalion Centers NCEL Special Distribution List No. 4 for persons and activities interested in reports on Deterioration Control 19 Set ME eer ie X0 pteaT ae age Unclassified Security Classification DOCUMENT CONTROL DATA-R&D (Security classification of title, body of abstract and indexing annotation niust be entered when the overall report is cli issifted) } yt ORIGINATING ACTIVITY (Corporate author) 2a. REFORT SECURITY CLASSIFICATION mpi es : : Unclassified Naval Facilities Engineering Command . . 26. GROUP \ 3. REPORT TITLE EFFECT OF BOTTOM SEDIMENT CONTAINING HYDROGEN SULFIDE ON MATERIALS - PART I 4. DESCRIPTIVE NOTES (Type of report and inclusive dates) Not final - August 1971 - November NOW 2 5. AUTHOR(S) (Firat name, middle initial, last name) James S. Muraoka 6. REPORT OATE Ja. TOTAL NO. OF PAGES 7b. NO. OF REFS March 1973 6a. CONTRACT OR GRANT NO 9a. ORIGINATOR S REPORT NUMBER(S) B PROJECTNO. YF 54,543.007.01.001 TN-1263 c. 9b. OTHER REPORT NO(S) (Any other numbers thet may be assigned thie report) 10. DISTRIBUTION STATEMENT Approved for public release; distribution unlimited 11. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY Naval Facilities Engineering Command 13. ABSTRACT Plastic, synthetic ropes, natural fiber ropes, electrical cable, insulations, and a wood panel were partially exposed in the black, bottom sediment of Port Hueneme Harbor to determine the effect of hydrogen sulfide on materials. After one year of exposure, the materials were recovered and examined for fouling and biodeteriora- tion. In addition, hardness and moisture absorption tests were conducted on the plastic panels while tensile strength tests were conducted on rope specimens. Significant changes in hardness and moisture absorption were registered by nylon and phenolic laminate plastics. Decrease in tensile strength was experienced by all of the synthetic rope specimens. The natural rope specimens were totally destroyed by marine organisms. The wood panel was riddled by marine borers. DD MerelasS RCE Unclassified S/N 0101+ 807-6801 Security Classification Unclassified Security Classification KEY WOROS | Hydrogen sulfied Sediments Ocean bottom Fouling | Biodeterioration Marine borers Aquatic animals Plastics Rope Wood DD ort..1473 (eack) de (PAGE 2) Security Classification