Iron cycling at corroding carbon steel surfaces

Surfaces of carbon steel (CS) exposed to mixed cultures of iron-oxidizing bacteria (FeOB) and dissimilatory iron-reducing bacteria (FeRB) in seawater media under aerobic conditions were rougher than surfaces of CS exposed to pure cultures of either type of microorganism. The roughened surface, demonstrated by profilometry, is an indication of loss of metal from the surface. In the presence of CS, aerobically grown FeOB produced tight, twisted helical stalks encrusted with iron oxides. When CS was exposed anaerobically in the presence of FeRB, some surface oxides were removed. However, when the same FeOB and FeRB were grown together in an aerobic medium, FeOB stalks were less encrusted with iron oxides and appeared less tightly coiled. These observations suggest that iron oxides on the stalks were reduced and solubilized by the FeRB. Roughened surfaces of CS and denuded stalks were replicated with culture combinations of different species of FeOB and FeRB under three experimental conditions. Measurements of electrochemical polarization resistance established different rates of corrosion of CS in aerobic and anaerobic media, but could not differentiate rate differences between sterile controls and inoculated exposures for a given bulk concentration of dissolved oxygen. Similarly, total iron in the electrolyte could not be used to differentiate treatments. The experiments demonstrate the potential for iron cycling (oxidation and reduction) on corroding CS in aerobic seawater media.     

Anticorrosion mechanism of Cr-doped nickel-base alloy in Br/O environment: a DFT study

ABSTRACT

Density functional theory was used to investigate the anticorrosion mechanism of Cr-doped nickel-base alloy in Br/O environment. The adsorption properties including adsorption energy, bond length and electron structure of Br/O on Ni and Cr-doped Ni surfaces have been investigated. We find that the O atom has bigger adsorption activity than the Br atom. The oxide film can be preferentially formed on the Cr-doped nickel-base alloy surface under the coexistence of Br and O atoms. By exploring the interactions between Br and NiO (111) or Cr₂O₃ (100) surfaces, we demonstrate that oxide films could prevent Br from erosion. Results indicate that Cr₂O₃ has stronger corrosion resistance than NiO. The corrosion resistance mechanism of Cr-doped nickel-base alloy is summarised into two processes, i.e. competitive adsorption and adsorption inhibition.     

Effects of seating load magnitude and load orientation on seating mechanics in 5°40′ mixed-alloy modular taper junctions

BackgroundMechanically-assisted crevice corrosion of modular tapers continues to be a concern in total joint replacements. Surgical factors that may affect taper seating mechanics include seating load magnitude and load orientation. Seating mechanics is defined as the seating load versus displacement behavior. In this study, mixed-alloy (CoCrMo/Ti-6Al-4V) modular head-neck 5°40′ taper junctions were seated over a range of axially-oriented loads and off-axis orientations, capturing load-displacement during seating. The goals of the study were to assess the effects of seating load magnitude and load orientation on seating mechanics and correlate those findings with the taper pull-off load.MethodsA testing fixture measured head-neck seating displacement as the load was quasistatically applied. Motion was captured using two non-contact differential variable reluctance transducers which were mounted to the neck targeting the head. Seating experiments ranged from 1000 N to 8000 N. Load orientation ranged from 0° to 20° at 4000 N.ResultsSeating load-displacement behavior at different seating loads showed a consistent characteristic behavior. Testing demonstrated increased seating displacement with seating load. Pull-off loads increased with seating load and were approximately 44% of the seating load across the range of seating loads investigated. Seating load orientation up to 20° had no significant effect on seating displacement and taper pull-off load.ConclusionIncreased seating load magnitude increased seating displacement, work of seating and pull-off loads in mixed-alloy 5°40′ head-neck tapers. Altering load orientation up to 20° off-axis had no significant effect. Direct measurements of seating mechanics provides insights into the locking of taper junctions.     

Identification and characterization of microbial biofilm communities associated with corroded oil pipeline surfaces

Microbially influenced corrosion (MIC) has long been implicated in the deterioration of carbon steel in oil and gas pipeline systems. The authors sought to identify and characterize sessile biofilm communities within a high-temperature oil production pipeline, and to compare the profiles of the biofilm community with those of the previously analyzed planktonic communities. Eubacterial and archaeal 16S rRNA sequences of DNA recovered from extracted pipeline pieces, termed ‘cookies,’ revealed the presence of thermophilic sulfidogenic anaerobes, as well as mesophilic aerobes. Electron microscopy and elemental analysis of cookies confirmed the presence of sessile cells and chemical constituents consistent with corrosive biofilms. Mass spectrometry of cookie acid washes identified putative hydrocarbon metabolites, while surface profiling revealed pitting and general corrosion damage. The results suggest that in an established closed system, the biofilm taxa are representative of the planktonic eubacterial and archaeal community, and that sampling and monitoring of the planktonic bacterial population can offer insight into biocorrosion activity. Additionally, hydrocarbon biodegradation is likely to sustain these communities. The importance of appropriate sample handling and storage procedures to oilfield MIC diagnostics is highlighted.     

Hybrid Composite Coatings for Durable and Efficient Solar Hydrogen Generation under Diverse Operating Conditions

Safe and practical solar‐driven hydrogen generators must be capable of efficient and stable operation under diurnal cycling with full separation of gaseous H₂ and O₂ products. In this study, a novel architecture that fulfills all of these requirements is presented. The approach is inherently scalable and provides versatility for operation under diverse electrolyte and lighting conditions. The concept is validated using a 1 cm² triple‐junction photovoltaic cell with its illuminated photocathode protected by a composite coating comprising an organic encapsulant with an embedded catalytic support. The device is compatible with operation under conditions ranging from 1 m H₂SO₄ to 1 m KOH, enabling flexibility in selection of semiconductor, electrolyte, membrane, and catalyst. Stable operation at a solar‐to‐hydrogen conversion efficiency of >10% is demonstrated under continuous operation, as well as under diurnal light cycling for at least 4 d, with simulated sunlight. Operational characteristics are validated by extended time outdoor testing. A membrane ensures products are separated, with nonexplosive gas streams generated for both alkaline and acidic systems. Analysis of operational characteristics under different lighting conditions is enabled by comparison of a device model to experimental data.     

壳聚糖-g-N.羧甲基-二(2-苯并眯唑)-1,2-乙二醇的制备及其性能

以2-溴乙酸、壳聚糖、二（2-苯并咪唑）-1,2-乙二醇为原料,利用接枝作用将化学修饰后的小分子药物二（2-苯并咪唑）-1,2-乙二醇连接在天然高分子壳聚糖（CTS）上。并以。HNMR,IR,热分析及XRD等方法对其结构进行表征并研究接枝聚合物的理化性质。本文采用络合滴定法测定了接枝聚合物对一系列重金属离子的吸附作用;采用震荡法进行悬菌定量杀菌实验;还以经典的静态失重法研究了合成的聚合物在腐蚀介质中对N80钢片腐蚀的抑制作用。结果表明：小分子药物-（2-苯并咪唑）-1,2-乙二醇在接枝到天然高分子壳聚糖后热稳定性提高,在酸中具有良好的溶解度,对金属离子吸附能力在一个较宽温度范围内得以保持;同时增强了抑菌力,降低了最小抑菌浓度;利用BBIE与CTS韵协同作用提高了聚合物对金属腐蚀的抑制能力。     

Bioenergetics of sulphate-reducing bacteria in relation to their environmental impact

The cellular physiology of the sulphate-reducing bacteria, and of other sulphidogenic species, is determined by the energetic requirements consequent upon their respiratory mode of metabolism with sulphate and other oxyanions of sulphur as terminal electron acceptors. As a further consequence of their, relatively, restricted catabolic activities and their requirement for conditions of anaerobiosis, sulphidogenic bacteria are almost invariably found in nature as component organisms within microbial consortia. The capacity to generate significant quantities of sulphide influences the overall metabolic activity and species diversity of these consortia, and is the root cause of the environmental impact of the sulphidogenic species: corrosion, pollution and the souring of hydrocarbon reservoirs.     

Three-dimensional organisation of the vasculature of the rat spermatic cord and testis

Summary The vascular architecture of the rat testis and spermatic cord was studied by a corrosion cast technique combined with scanning and transmission electron microscopy, and light microscopy. The casts preserve the endothelial impressions of the vessels and enable them to be differentiated into the various vascular components. Frequent arterio-arterial anastomotic arcades and occasional arterio-venous anastomotic channels are seen. A well defined hexagonal pattern of intertubular and peritubular vessels surround the seminiferous tubules. Prominent large endothelial nuclei protrude into the arterial lumina at branching sites, but their functional significance is not known. The outermost vascular layer of the testis consists of large veins, venules, and capillaries, but lacks any arterial branches; it also contains loosely arranged veno-venous anastomotic networks. We have named this vascular layer the sub-albugineal venous plexus. The testicular artery increases in luminal diameter as it approaches the testis. The periarterial capillary plexus, which lies between the pampiniform plexus and the testicular artery, is drained by two types of venules.     

Fungal polysaccharopeptide inhibits tumor angiogenesis and tumor growth in mice

Angiogenesis is crucial to tumor growth and metastasis, and interruption of this process is a prime avenue for therapeutic intervention of tumor proliferation. The present study has made use of the S180 tumor-bearing mouse model to investigate the polysaccharopeptide, PSP, isolated from the edible mushroom Coriolus versicolor, a herbal medicine known for its anti-angiogenesis properties. Quantitative analysis of microcorrosion casting of the tumor tissue showed more angiogenic features such as dense sinusoids and hot spots, in control (untreated) than in PSP-treated animals. Immunostaining of tumor tissues with antibody against the endothelial cell marker (Factor VIII) demonstrated a positive correlation in that both the vascular density and tumor weight were lower in mice treated with PSP. Morphometric analysis of corrosion casts revealed that, even though the total amount of new vessel production was reduced, the basic tumor type-specific vascular architecture was retained. However, the expression of vascular endothelial cell growth factor (VEGF) in these tumors was suppressed. In conclusion, anti-angiogenesis should be one of the pathways through which PSP mediated its anti-tumor activity.