Browsing by Keyword "Corrosion"
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Item Bonding strength of stainless steel rebars in concretes exposed to marine environments(2018-05-30) Calderon-Uriszar-Aldaca, I.; Briz, E.; Larrinaga, P.; Garcia, H.; Tecnalia Research & InnovationMany studies have corroborated the use of Stainless Steel Reinforcements (SSR) for structures in corrosive environments. However, even though the conditions for their employment are specified in different standards, their use is always tied to the same requirements for standard carbon steel rebars (B500SD), among which an equivalent carbon content for weldability that is inappropriate for SSR. Further studies are therefore needed to develop suitable standards that will focus on addressing not only the content, but also the technical advantages of SSR for structural engineering under specific conditions. The results of this study show improvements in the maximum bond strength behaviour of different SSRs in simulated marine environments, in comparison with B500SD, in terms of several variables: Bond index, curing time, w/c ratio, and corrosion. Specifically, the test results showed that: (a) the Bond index was not a suitable parameter for the evaluation of the bonding strength of SSR; (b) the curing time increased the bonding strength of Lean Duplex Stainless Steel (LDSS); (c) a higher w/c ratio tended to decrease bond strength, although less so in LDSS; and, (d) corrosion reduced bond strength, especially in B500SD.Item Central lessons from the historical analysis of 24 reinforced-concrete structures in northern Spain(2016-07-01) Marcos, Ignacio; San-José, José Tomás; Garmendia, Leire; Santamaría, Amaia; Manso, Juan Manuel; Tecnalia Research & InnovationSince the late-nineteenth century, the use of reinforced-concrete as a structural material has proliferated and is now commonplace in the modern built environment. Some of the structures from that century are even considered cultural heritage. In the early stages of its technical development, concrete was seen as practically immutable over time; however, prolonged exposure to environmental agents has revealed its very significant problems of weakening strength and durability. A total of 24 aging reinforced-concrete structures in the Basque Country (northern Spain) and their behavior over time are analyzed in this paper. Reference is made to pathological reports, categorized for the purposes of this study, which characterize their concrete and steel components. This contribution greatly enhances our knowledge of each structure for future studies and for the improvement of their conservation strategies.Item Corrosion performance of alloy 800H and alloy 625 for potential use as molten salts solar receiver materials in concentrating solar power tower plants(2022-11-30) Prieto, Cristina; Ruiz-Cabañas, F. Javier; Madina, Virginia; Fernández, A. Inés; Cabeza, Luisa F.; MATERIALES PARA CONDICIONES EXTREMASTwo high corrosion resistant super-alloys, alloy 800H and alloy 625, were evaluated for corrosion compatibility with molten nitrate salts at 565 °C under air atmosphere since these super-alloys are possible candidates for the manufacturing of molten salts solar receivers in the CSP tower technology. Both alloys are tested in two different molten nitrate salts grades to identify how the impurities of the final mixture affect to corrosion damage. Accordingly, a technical grade molten nitrate salt (Solar_Salt_T) and refined molten nitrate salt (Solar_Salt_R) are selected as test media. In addition to corrosion rates calculation, techniques such as XRD, EDS, optical and scanning electron microscopy are used to identify the corrosion morphology and oxides layers chemistry. Alloy 800H and alloy 625 show uniform corrosion after testing without detecting localized phenomena such as pitting, stress corrosion cracking, crevice, or intergranular corrosion. While alloy 800H develops a duplex oxide layer consisting of iron oxides in its external part, and chromium oxide in its innermost layer, alloy 625 generates a compact and highly adherent oxide layer consisting mainly of nickel oxide. Corrosion rates decrease with time, being higher for alloys exposed to Solar_Salt_T mixtures. Moreover, alloy 625 shows lower corrosion rates than alloy 800H in all conditions tested in this study.Item Corrosion preserving high density plasma treatment of precipitation hardening stainless steel(2018-12-15) Braceras, Iñigo; Ibáñez, Iñigo; Domínguez-Meister, Santiago; Urgebain, Aiala; Sánchez-García, Jose Angel; Larrañaga, Aitor; Garmendia, Iñaki; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIES; MATERIALES PARA CONDICIONES EXTREMASSpecialty alloys such as precipitation hardening stainless steels are routinely used in critical applications requiring high strength and corrosion resistance, e.g. in aeronautics, in ground transportation and the biomedical field. Nonetheless, their tribological properties remain poor, while the application of surface treatments results in loss of corrosion resistance. Therefore, typically a not fully satisfactory compromise must be adopted. In the present work, the improvement of tribological features, without loss of corrosion resistance, of the 1.4545 (15-5PH) steel has been explored with the use of high density plasmas. The work has focused on long cylindrical geometries, close to those of real applications. The microstructure and composition of the treated surfaces were studied and the corresponding corrosion resistance stablished. The characteristics of the high density plasmas as well as the sample disposition were key factors in the outcomes, which ranged from fully corroded to corrosion resistant surfaces. Results also showed in certain cases the high density plasmas causing surface cracks followed by local corrosion. Additionally tribological studies demonstrated improvement in wear resistance, and electrical contact resistance (ECR) was found to be a good indicator of the wear phenomena occurring along the tests. An equivalent electric circuit is proposed. Actually ECR could be a useful and simple way of monitoring the surface status and assist in assuring safe and dependable operational lives of the components. In conclusion, treatment conditions of cylindrical 1.4545 (15-5PH) have been defined, which provide with an improved tribological performance, preserving corrosion resistance, with ECR a useful performance monitoring parameter.Item Durability studies on steelmaking slag concretes(2014-11) Arribas, Idoia; Vegas, Iñigo; San-Jose, Jose Tomas; Manso, Juan M.; TRAZABILIDAD CIRCULAR; GENERALElectric-arc furnace slag is proposed as a substitute for the conventional aggregate used in classical structural concrete. In the present research is studied the durability of these slag aggregate concretes and their resistance to both physical (freeze–thaw, high temperature and relative humidity) and chemical degradation (sulfate attack, alkali–aggregate reaction and marine environment), as well as their resistance to the corrosion of steel reinforcement bars (an assessment of the risks of corrosion) embedded in the concrete matrix. This approach requires laboratory studies. The main objective of this work focuses on evaluating the durability of slag concrete under the conditions specified in the Spanish structural concrete code. In general terms, the behavior of the concrete with slag aggregate was similar to or better than the reference concrete (natural aggregate), except in case of exposure to marine environments and seawater, which resulted in quicker chloride penetration. The study confirms the viability of producing steel-reinforced concrete with slag aggregate.Item Effect of high‐density current electropulsing on corrosion cracking of titanium aluminide intermetallic(Wiley-VCH Verlag, 2021-02-05) Babutskyi, Anatolii; Chrysanthou, Andreas; Chyzhyk, Ganna; Cortázar, Maider García; Egizabal, Pedro; Smelina, MarijaThe effect of electropulsing on the corrosion cracking of titanium aluminide produced by self‐propagating high‐temperature synthesis has been investigated. The electropulsing treatment led to improved corrosion resistance in sodium fluoride solution and also eliminated corrosion cracking at the α2/γ interface during corrosion in a solution of nitric and hydrofluoric acids. This behavior was attributed to thermal and athermal effects resulting from electropulsing and leading to the interaction of conduction electrons with the defect structure. The effect of magnetic field accompanying electropusling on depinning of dislocations also has been discussed. Support for this is provided on the basis of X‐ray diffraction analysis and microhardness testing.Item Encapsulated high temperature PCM as active filler material in a thermocline-based thermal storage system(2015-05-01) Muñoz-Sánchez, B.; Iparraguirre-Torres, Iñigo; Madina, Virginia; Izagirre, Usoa; Unzurrunzaga-Iturbe, A.; García-Romero, A.; Madina-Arrese, V.; Izagirre-Etxeberria, U.; Tecnalia Research & Innovation; MATERIALES PARA CONDICIONES EXTREMAS; INGENIERÍA DE SUPERFICIES; VALORIZACIÓN DE RESIDUOSA great concern in Concentrated Solar Power (CSP) is to boost energy harvesting systems, by finding materials with enhanced thermal performance. Phase Change Materials (PCM) have emerged as a promising option, due to their high thermal storage density compared to sensible storage materials currently used in CSP. A thermal storage system for solar power plants is proposed, a thermocline tank with PCM capsules together with filler materials, based on multi-layered solid-PCM (MLSPCM) thermocline-like storage tank concept [1,2]. A detailed selection of the most suitable high temperature PCM, their containment materials and encapsulation methods are shown.Item High temperature corrosion behavior on molten nitrate salt-based nanofluids for CSP plants(2019-01) Fernández, Angel G.; Muñoz-Sánchez, Belen; Nieto-Maestre, Javier; García-Romero, Ana; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOSRecently, a number of theoretical and experimental studies have been performed to understand the effect of nanoparticles on thermal properties and heat transfer performance but there is a lack regarding their corrosion properties. In this work, an extended corrosion characterization (at central tower plant storage temperature (565 °C)) has been carried out in two different grades of solar salt (industrial and refined purity) doped with the addition of 1 wt% Al2O3 nanoparticles or 1 wt% SiO2 nanoparticles. Corrosion rates were determined in commercial stainless steel commonly used in CSP technology (347SS) by gravimetric tests, measuring the weight gain during 1000 h, identifying the corrosion products by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The lowest corrosion rate (0.007 mm/year) was obtained in the refined solar salt with the addition of 1 wt% Al2O3 nanoparticles. A protective layer was formed in the steel-salt interphase, identified through XRD as Al2O3.Item Materials selection for thermal energy storage systems in parabolic trough collector solar facilities using high chloride content nitrate salts(2017-04-01) Ruiz-Cabañas, F. Javier; Prieto, Cristina; Madina, Virginia; Fernández, A. Inés; Cabeza, Luisa F.; MATERIALES PARA CONDICIONES EXTREMASThe increasing role of concentrated solar power (CSP) within the renewable energy portfolio is attributed to the possibility of integrating thermal energy storage (TES) systems. Then, CSP technology has become one of the most interesting clean options to deliver dispatchable power on demand. Nowadays, commercial facilities use high quality solar salts (60%:40% NaNO3 and KNO3 by weight) as storage medium due to the attractive properties of this fluid to be applied under CSP operation conditions. Taking into account that CSP installations are designed with really large TES systems containing tens of thousands of tons, the use of lower quality nitrates salts would reduce the molten salts inventory cost and finally the investment cost of the CSP storage systems at commercial scale. The most important drawback of selecting low quality nitrates salts for high temperature CSP applications is the corrosion impact produced by impurities. Accordingly, chlorides have been identified in the state of the art as the impurity with higher effect over corrosion. This work is focused on A516 Gr70 carbon steel corrosion performance evaluation under high-chlorides content nitrates salts (1.2% and 3% by weight) at 400 °C. In addition, the feasibility of using the proposed low purity mixtures with current CSP facilities materials selection is analyzed. Results reported within this study show the critical effect of chloride content over corrosion mechanism producing lack of adherence between base metal and oxides layers in addition to corrosion products delamination and internal cracking. Then, the use of A516 Gr70 carbon steel is rejected for a long term design under solar salts containing chlorides content in the range 1.2–3% by weight being necessary a higher corrosion resistant materials selection. An improved materials selection focused on higher corrosion resistance alloys is discussed.Item Materials selection of steam-phase change material (PCM) heat exchanger for thermal energy storage systems in direct steam generation facilities(2017-01-01) Ruiz-Cabañas, F. Javier; Jové, Aleix; Prieto, Cristina; Madina, Virginia; Fernández, A. Inés; Cabeza, Luisa F.; MATERIALES PARA CONDICIONES EXTREMASPhase change materials (PCM) is one of the most interesting solutions to be used in thermal energy storage (TES) systems for direct steam generation (DSG) thermosolar facilities. Properties such as high energy density and energy storing/delivery at constant temperature bring PCM based systems in excellent candidates for DSG facility storage units. Accordingly, LiOH-KOH peritectic mixture, with a melting point of 315 °C and an enthalpy change of 535 kJ/kg, has been reported as attractive solution for the saturated storage module in DSG plants. A steam-PCM heat exchanger is the critical component to carry out the thermal transference between both substances. Although materials selection to be applied for steam applications is well known, lack of knowledge is detected in the field of high temperature hydroxides corrosion. Therefore, three metallic materials, A516 Gr70 carbon steel, A316L stainless steel and Inconel 625 Ni-base alloy, have been evaluated to determine their corrosion performance after hydroxides exposure. While A516 Gr70 was discarded for this application due to high corrosion rates, A316L and Inconel 625 displayed good corrosion resistance after 2640 h. Finally, A316L stainless steel was selected as potential candidate for the construction of the steam-PCM heat exchanger considering cost and thermal efficiency optimization.Item Superhydrophobic and oleophobic microtextured aluminum surface with long durability under corrosive environment(2023-01-31) Adarraga, Olatz; Agustín-Sáenz, Cecilia; Bustero, Izaskun; Brusciotti, Fabiola; Tecnalia Research & Innovation; PRINTEX; VALORIZACIÓN DE RESIDUOS; INGENIERÍA DE SUPERFICIESSuperhydrophobic (SHP) and oleophobic aluminum surfaces have been prepared through the combination of a scalable chemical microtexturing process and surface functionalization with long-chained polyfluoroalkyl moieties. The effect of an anodic layer on the microtextured surface has been assessed considering surface morphology, superhydrophobicity, surface mechanical properties and corrosion protection enhancement. The surface functionalization with polyfluoroalkyl moieties has been tackled in two different ways: (i) grafting of the polyfluoroalkyl moieties and (ii) deposition of a thin hybrid coating with low content of polyfluoroalkyl-containing compound. Aluminum surfaces showing high durability in salt spray environments, which maintain SHP and oleophobic properties at least up to 2016 h have been attained. Applications for this kind of surfaces range from easy-to-clean surfaces to anti-icing or anti-condensation functionalities that could be of interest for several sectors.