Corrosive environment in the annulus of flexible pipes: pH measurements in confined conditions and under high pressure

International audienceAnnulus of flexible pipelines represents a specific corrosive environment for the high strength carbon steel wires, mainly due to the low V/S ratio between the volume of electrolyte and the exposed steel surface. Corrosion experiments with continuous in situ pH measurements were performed under CO 2 partial pressure from 0.01 bar and up to 10 bar, and with a V/S ratio of 0.3 mL/cm². After only a few days immersion, supersaturated pH was measured at levels close to +1 pH unit above the saturated pH calculated corresponding to iron carbonate solubility. Good correlation was found between experiments and a pH and corrosion model specially developed for confined environment. This model predicts that the corrosion rate in super-saturated conditions is considerably reduced in comparison with bulk situation. Long term behavior was also examined. It appears that the evolution of super-saturated pH with time passes by a maximum value, then decreases slowly to a new equilibrium. It was postulated that the maximum corresponds to a fully active surface. Then, as precipitation occurs, corrosion rate is decreased by corrosion scale. The decrease of corrosion rate could be quantified from the final pH value: value as low as a few µm/year was found. Even with such low corrosion rates, high confinement still induced super-saturation effect, with final pH values at +0.5 pH units above saturated pH

Prediction of the flexible pipe annulus pH at high CO2 content and high temperature

International audiencePrevious works have shown that the typical ratio between the volume of electrolyte and the exposed steel surface observed in the annulus of flexible pipelines leads to a specific corrosive environment whose pH deviate from the classical thermodynamic models. In this case, due to the supersaturation in iron ions in the annulus, the commercial models even with their most recent updates cannot precisely predict the measured pH. Due to these specificities, tests are necessary to overcome these limitations and to improve with a better accuracy the pH considered in the design of the flexible pipes. Nowadays, with the development of the Brazilian oil and gas pre-salt basins, a high CO2 partial pressure associated with high temperature are observed in the flexible pipe annulus. Due to the lack of experimental data concerning the pH evolution under these conditions, tests were carried out with a continuous pH monitoring at CO2 partial pressure and temperature up to, respectively, 70 bara and 84 °C. The test results presented in this article show an amplitude between the experimental data and the predicted pH values of at least +0.4 pH units which confirms the conservatism of the thermodynamic models at saturation. In all the tests, the pH reached a maximum value after the first days of immersion followed by a decrease and fast stabilization after this event. An impact of the temperature was verified on the pH behavior in these tests. Keywords Flexible pipes; annulus pH; high pressure; high temperature

A study by in situ Raman spectroscopy of carbon steel corrosion in CO2 and H2S environment

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Multifunctional biomaterials from the sea: Assessing the effects of chitosan incorporation into collagen scaffolds on mechanical and biological functionality

Natural biomaterials such as collagen show promise in tissue engineering applications due to their inherent bioactivity. The main limitation of collagen is its low mechanical strength and somewhat unpredictable and rapid degradation rate; however, combining collagen with another material, such as chitosan, can reinforce the scaffold mechanically and may improve the rate of degradation. Additionally, the high cost and the risk of prion transmission associated with mammal-derived collagen has prompted research into alternative sources such as marine-origin collagen. In this context, the overall goal of this study was to determine if the incorporation of chitosan into collagen scaffolds could improve the mechanical and biological properties of the scaffold. In addition the study assessed if collagen, derived from salmon skin (marine), can provide an alternative to collagen derived from bovine tendon (mammal) for tissue engineering applications. Scaffold architecture and mechanical properties were assessed as well as their ability to support mesenchymal stem cell growth and differentiation. Overall, the addition of chitosan to bovine and salmon skin-derived collagen scaffolds improved the mechanical properties, increasing the compressive strength, swelling ratio and prolonged the degradation rate. Mesenchymal stem cell (MSC) attachment and proliferation was most improved on the bovine-derived collagen scaffold containing a 75:25 ratio of collagen:chitosan, and when MSC osteogenic and chondrogenic potential on the scaffold was assessed, a significant increase in calcium production (p < 0.001) and sulfated glycosaminoglycan (sGAG) production (p < 0.001) was observed respectively. Regardless of chitosan content, the bovine-derived collagen scaffolds out-performed the salmon skin-derived collagen scaffolds, displaying a larger pore size and higher percentage porosity, more regular architecture, higher compressive modulus, a greater capacity for water uptake and allowed for more MSC proliferation and differentiation. This versatile scaffold incorporating the marine biomaterial chitosan show great potential as appropriate platforms for promoting orthopaedic tissue repair while the use of salmon skin-derived collagen may be more suitable in the repair of soft tissues such as skin.This work was funded by Science Foundation Ireland (SFI) through the Research Frontiers Programme (Grant No. 11/RFP/ENM/3063) and by the European Regional Development Fund (ERDF) through INTERREG 2007-2013 Program (POCTEP project 0687_NOVOMAR_1_P). Bovine collagen materials were provided by Integra Life Sciences, Inc. through a Material Transfer Agreement. Salmon skins were kindly offered by Pingo Doce, Braga (Portugal)

Chitin-based Materials in Tissue Engineering: Applications in Soft Tissue and Epithelial Organ

Chitin-based materials and their derivatives are receiving increased attention in tissue engineering because of their unique and appealing biological properties. In this review, we summarize the biomedical potential of chitin-based materials, specifically focusing on chitosan, in tissue engineering approaches for epithelial and soft tissues. Both types of tissues play an important role in supporting anatomical structures and physiological functions. Because of the attractive features of chitin-based materials, many characteristics beneficial to tissue regeneration including the preservation of cellular phenotype, binding and enhancement of bioactive factors, control of gene expression, and synthesis and deposition of tissue-specific extracellular matrix are well-regulated by chitin-based scaffolds. These scaffolds can be used in repairing body surface linings, reconstructing tissue structures, regenerating connective tissue, and supporting nerve and vascular growth and connection. The novel use of these scaffolds in promoting the regeneration of various tissues originating from the epithelium and soft tissue demonstrates that these chitin-based materials have versatile properties and functionality and serve as promising substrates for a great number of future applications

Photocrosslinkable gelatin hydrogels modulate the production of the major pro-inflammatory cytokine, TNF-α, by human mononuclear cells

Hydrogels are an attractive class of biomaterials in tissue engineering due to their inherently compatible properties for cell culture. Gelatin methacryloyl (GelMA) has shown significant promise in the fields of tissue engineering and drug delivery, as its physical properties can be precisely tuned depending on the specific application. There is a growing appreciation for the interaction between biomaterials and cells of the immune system with the increasing usage of biomaterials for in vivo applications. Here, we addressed the current lack of information regarding the immunogenicity of photocrosslinked GelMA. We investigated the ability of human mononuclear cells to mount inflammatory responses in the context of a GelMA hydrogel platform. Using lipopolysaccharide to stimulate a pro-inflammatory immune response, we found tumour necrosis factor-α (TNF-α) expression was suppressed in GelMA culture conditions. Our findings have important implications on the future use of GelMA and highlight the significance of investigating the potential immune-modulatory properties of biomaterials

Approaches in biotechnological applications of natural polymers

Natural polymers, such as gums and mucilage, are biocompatible, cheap, easily available and non-toxic materials of native origin. These polymers are increasingly preferred over synthetic materials for industrial applications due to their intrinsic properties, as well as they are considered alternative sources of raw materials since they present characteristics of sustainability, biodegradability and biosafety. As definition, gums and mucilages are polysaccharides or complex carbohydrates consisting of one or more monosaccharides or their derivatives linked in bewildering variety of linkages and structures. Natural gums are considered polysaccharides naturally occurring in varieties of plant seeds and exudates, tree or shrub exudates, seaweed extracts, fungi, bacteria, and animal sources. Water-soluble gums, also known as hydrocolloids, are considered exudates and are pathological products; therefore, they do not form a part of cell wall. On the other hand, mucilages are part of cell and physiological products. It is important to highlight that gums represent the largest amounts of polymer materials derived from plants. Gums have enormously large and broad applications in both food and non-food industries, being commonly used as thickening, binding, emulsifying, suspending, stabilizing agents and matrices for drug release in pharmaceutical and cosmetic industries. In the food industry, their gelling properties and the ability to mold edible films and coatings are extensively studied. The use of gums depends on the intrinsic properties that they provide, often at costs below those of synthetic polymers. For upgrading the value of gums, they are being processed into various forms, including the most recent nanomaterials, for various biotechnological applications. Thus, the main natural polymers including galactomannans, cellulose, chitin, agar, carrageenan, alginate, cashew gum, pectin and starch, in addition to the current researches about them are reviewed in this article.. }To the Conselho Nacional de Desenvolvimento Cientfíico e Tecnológico (CNPq) for fellowships (LCBBC and MGCC) and the Coordenação de Aperfeiçoamento de Pessoal de Nvíel Superior (CAPES) (PBSA). This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and COMPETE 2020 (POCI-01-0145-FEDER-006684) (JAT)