The attractiveness of additive manufacturing (AM) relates to the ability of this technology to ra... more The attractiveness of additive manufacturing (AM) relates to the ability of this technology to rapidly produce very complex components at affordable costs. However, the properties and corrosion behavior, in particular, of products produced by AM technology should at least match the properties obtained by conventional technologies. The present study aims at evaluating the corrosion behavior and corrosion fatigue endurance of AlSi10Mg alloy produced by selective laser melting (SLM) in comparison with its conventional counterpart, gravity cast alloy. The results obtained indicate that the corrosion resistance of the printed and cast alloys was relatively similar, with a minor advantage to the printed alloy. The corrosion fatigue endurance of the printed alloy was relatively improved compared to the cast alloy. This was mainly attributed to the significant differences between the microstructure and defect characteristics of those two alloys.
The paper is devoted to the study of stress corrosion cracking phenomena in friction stir welding... more The paper is devoted to the study of stress corrosion cracking phenomena in friction stir welding AA-2024 T3 joints. Constant load (CL) cell and slow strain rate (SSR) tests were carried out in aerated NaCl 35 g/L solution. During the tests, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were measured in the different zones of the welding. The results evidenced initial practical nobilty of the nugget lower compared to both heat-affected zone and the base metal. This effect can be mainly ascribed to the aluminum matrix depletion in copper, which precipitates in form of copper-rich second phases. In this zones, no stress corrosion cracking was noticed, but well-evident stress-enhanced intergranular corrosion occurred. This is due to the uneven distribution of platic deformation during the slow strain rate tests. Higher strain values are localized at the heat affected zone, where softening occurs. On the contrary, stress values at the nugget are not sufficient to favor both the initiation and propagation of stress corrosion cracks. In the range of processing parameter studied in this experimental work, the stress corrosion cracking susceptibility of the friction stir welding (FSW)-ed alloy is then similar to that of the base metal.
In this paper, synergistic effects of chloride (Cl-) and thiosulfate (S 2 O 3 2-) on corrosion re... more In this paper, synergistic effects of chloride (Cl-) and thiosulfate (S 2 O 3 2-) on corrosion resistance of additively manufactured (AM) and wrought 316L stainless steel (SS) were investigated in ammonium chloride (NH 4 Cl) solution in the absence and presence of different concentrations of sodium thiosulfate (Na 2 S 2 O 3). General corrosion induced by Claccelerated with the increase of S 2 O 3 2concentration for both of the samples. However, pitting resistance of AM 316L SS was found to be at least 4-to 6-fold higher than that of the wrought sample depending on S 2 O 3 2concentration. The AM sample demonstrated significantly improved metastable pitting resistance in the presence of S 2 O 3 2into Clsolution. In addition, the passive film of AM 316L SS offered higher charge transfer resistance and film resistance confirming its better stability and barrier characteristics in Cl-S 2 O 3 2environment. The superior corrosion resistance of AM 316 L SS compared to wrought sample was attributed to refined microstructure, absence of MnS micro-inclusions, and lack of Cr depleted regions.
This paper deals with variability in the performance of seven different superplasticizers that we... more This paper deals with variability in the performance of seven different superplasticizers that were chosen among those of most common use belonging to the naphthalene (NSF) and polycarboxylate-based (PCE) families. In particular, compatibility of two naphthalene-based and five polycarboxylate-based admixtures with six different cements available on the Italian market was evaluated by measuring water reduction to manufacture mortars with the same workability at the end of mixing. Two different lots of the same cement (same plant) were used: lot 1 and 2 produced, on September 2005 and March 2006 respectively. Flow attention up to sixty minutes and tendency to entrap air in the mortars were measured. Results confirmed that the average water reduction and flow retention properties are better for PCE compare to NSF superplasticizers. However, experimental data confirm as the performance of PCE admixtures are more strongly dependent on the cement type than those of NSF polymers. No differences were detected in terms of the air entrapped between the two superplasticizer families, except for the ACR(5) superplasticizer.
The paper deals with the effect of heat treatments on corrosion resistance of an AlSilOMg alloy o... more The paper deals with the effect of heat treatments on corrosion resistance of an AlSilOMg alloy obtained by means of Direct Metal Laser Sintering. The tests were performed on as-processed alloy and after different post-heat treatment, covering stress relieving, annealing at high temperature and water quenching. Potentiodynamic and electrochemical impedance spectroscopy tests were carried out in aerated Harrison solution. The results show localized corrosion and selective penetrating attack at the border of melt pools on untreated or only stress relieved specimens. The selective attack was not observed after high temperature annealing. Modification of EIS plot evidenced galvanic coupling with silicon coarse particles that extensively precipitate during high temperature annealing. The morphology of precipitates is described in order to evidence their relevance in terms of rising selective penetrating attack and galvanic coupling.
The present study was carried out to evaluate how the process parameters affect the mechanical pr... more The present study was carried out to evaluate how the process parameters affect the mechanical properties and the corrosion behavior of joints obtained by friction stir welding (FSW). The experimental study was performed by means of a CNC machine tool for the friction stir welding of two aluminum alloys, namely AA7075 and AA2024, taking also into account the combination between the two materials. The joints were executed varying the process parameters, namely rotational speed and feed rate. Tensile tests and hardness tests were carried out to evaluate the mechanical properties of the joints. The corrosion behavior of welded specimens was analyzed by means of local free corrosion potential measurements to determine anodic and cathodic areas of welds. The results evidenced that the low hardness areas have the free corrosion potential more anodic than the nearest zones. The differences of potential between the different areas of the welding have the consequence of galvanic corrosion of the less noble area. The location and the extension of the anodic areas depend both on the alloy and on the welding parameters. The preferentially corrosion of these areas were confirmed by means of long time immersion tests. The attacks morphology depends on the alloy: in AA2024 a severe crevice and pitting attack takes place, whereas the AA7075 shows exfoliation corrosion along the rolling bands. Coupling the two different alloys, a severe galvanic attack takes place on the AA7075, in the correspondence of the lower hardness areas. The decreasing of hardness and the different electrochemical behavior in the correspondence of the welding were due to the microstructural alteration of the alloys during the FSW. The correlation between process parameters and joints properties allowed to identify the most suitable welding conditions.
The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-co... more The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-compressing structures can promote localized attacks as a function of pH. The aggressive local environment in the occluded cells inside localized attacks has as consequence the possibility of initiation of stress corrosion cracking. In this paper, the stress corrosion cracking behavior of high strength steels proposed for tendons was studied by means of Constant Load (CL) tests and Slow Strain Rate (SSR) tests. Critical ranges of pH for cracking were verified. The promoting role of localized attack was confirmed. Further, electrochemical tests were performed on bars in as received surface conditions, in order to evaluate pitting initiation. The adverse effect of mill scale was recognized.
Calcium chloride is one of the main de-icing salts for removing snow and ice from roads, infrastr... more Calcium chloride is one of the main de-icing salts for removing snow and ice from roads, infrastructures and service areas. It is well known that reinforced concrete structures, if exposed to calcium chloride, can suffer from severe damages due to both corrosion of steel reinforcement and chemical attack of the cement paste. This paper aims at evaluating the resistance to chemical attack of mortars manufactured with different low-carbon binders (alkali activated slag cements, calcium sulphoaluminate cement-based blends, high volume ultrafine fly ashes cements) in presence of CaCl2-based de-icing salts in cold weather (temperature about 4°C). Results indicated that alkali activated slag-based mortars are quasi-immune to calcium chloride attack due to their mineralogical composition. On the contrary, calcium sulphoaluminate-based blends show the total loss of binding capacity, especially when calcium sulphoaluminate cement is used with gypsum and Portland cement. Finally, the partial substitution of Portland cement with ultrafine fly ash strongly reduces the mass change and the strength loss of mortars submerged in 30 wt.% CaCl2 solutions due to the strong reduction of calcium hydroxide responsible for the calcium oxychloride formation in the cement paste.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The paper reports the results of an experimental work on the effect of steel microstructures on m... more The paper reports the results of an experimental work on the effect of steel microstructures on morphology and protectiveness of the corrosion scale formed in water saturated by supercritical CO 2. Two HSLA steels were tested. The microstructures were modified by means of different heat treatments. Weight loss was measured after exposure at CO 2 partial pressure of 80 bar and 60 ∘ C temperature. The morphology of the scale was analyzed by means of scanning electron microscope (SEM) energy-dispersive X-ray spectroscopy (EDX). Cathodic potentiodynamic tests were carried out on precorroded specimens for evaluating the effect of preformed scales on cathodic polarization curves in CO 2 saturated sulphuric acid solution at pH 3, which is the value estimated for water saturated by supercritical CO 2. The results are discussed in order to evaluate the effect of iron carbide network on scale growth and corrosion rate. Weight loss tests evidenced average corrosion rate values in the range 1-2.5 mm/y after 150-hour exposure. The presence of thick siderite scale significantly reduces the corrosion rate of carbon steel. A slight decrease of the corrosion rate was observed as the scale thickness increases and moving from martensite to microstructures containing carbides.
perform their role through three main components: a biocompatible scaffold, cellular component an... more perform their role through three main components: a biocompatible scaffold, cellular component and bioactive molecules. Nanotechnology, using advanced manufacturing techniques such as conventional and unconventional lithography, allows fabricating supports with geometries, sizes and displaying physical chemical properties tuneable over different length scales. In this work we report the fabrication of scaffolds made of fibrin gel and squid pen chitin, for the regeneration of tissues. Materials and methods: Fibrin gel films are used to observe the growth of cells on random networks. Films of different thickness have been fabricated with special attention to the realization of a micro-frame that allows a simple manipulation of the structure. Such a standing fibrin scaffold prevents the artefacts arising from the interaction of the films with other surfaces. The fibrin gel clots have then been stretched to observe if the cells growth and migration is influenced by the orientation of the fibers. Fabricating a scaffold via bottom-up techniques to mimic tissues is not simple. We have chosen to adopt a top-down strategy using a scaffold manufactured by nature and composed of extremely ordered chitin fibers: squid pen. The squid's pen is a support consisting of chitin fibers transparent, biocompatible, low cost and displaying high mechanical resistance. We have changed the chemical and physical properties of the scaffold to promote cell adhesion. Both supports were functionalized with retinoic acid to obtain a support able to induce cell differentiation. We characterized the scaffolds by scanning electron microscopy and immunofluorescence technique. Results: We have fabricated two types of scaffolds and we have observed cell growth on both scaffolds. We fabricated active scaffolds able to differentiate the stem cells into neuronal cells. The ultrastructure characterization of the scaffolds is crucial for evaluating their morphology, porosity and biological efficacy. Power spectrum analyses of the images have been performed to provide the characteristic lengths of the supports. Discussion: An important goal of this work was the fabrication of 3D scaffolds with a well-defined morphology to be used as a starting point for the regeneration of portions of tissue. The realization of a fibrin scaffold, of different thickness and easy to handle fabricated under controlled spatial confinement has been demonstrated. Characterization of the fibrin network has helped us to understand how the morphology of fibrin network might affect the cell growth. We propose the squid pen as a scaffold because it is biocompatible, transparent, it withstands surgical sutures and, moreover, it is a waste material of the industrial chain. The purpose is to exploit as much as possible the original remarkable properties provided by the structure of squid pen chitin to obtain a scaffold transparent and able to support all the mechanical stress. Furthermore, in a period characterized by the necessity of producing goods by a sustainable chemistry and a green economy, finding the way for using an available natural biomass has become a must for all scientists and industrial manufacturers.
Introduction: Pipelines and offshore applications, operating under cathodic protection to prevent... more Introduction: Pipelines and offshore applications, operating under cathodic protection to prevent general corrosion, are usually realized with High Strength Low Alloy (HSLA) steels. The risk of hydrogen embrittlement (HE) in pipeline steels due to cathodic overprotection are described in literature. HE is related to absorption and subsequent diffusion of atomic hydrogen through the lattice. On HSLA steels, HE occurs only in dynamic load conditions in the plastic field, such as slow strain rate or corrosion fatigue. Many studies were carried out on the effect of applied stress on hydrogen diffusion and HE mechanism but, at present, the phenomena are not fully understood. In this work, the effect of cyclic load in the elastic field on passivity current (iP) and hydrogen steady state permeation current (iHss) is reported. Materials and Methods: The permeation tests were carried out on API 5L X65 steel, according to ISO 17081:2014. The specimen acts as bi-electrode between the two compartments of the Devanathan-Stachurski cell. In the anodic compartment, it is polarized at +340 mV vs Ag/AgCl in a 0.1 M NaOH solution. The cathodic compartment is filled with a borate solution (pH 8.5) and a cathodic current density of 2 mA/cm2 was applied once passivity current reached values below 0.05 µA/cm2. Tests in unloaded conditions and under cycling load up to 80% TYS in the frequency range between 10-2 Hz and 1 Hz were performed. Results and Discussion: Tests realized in unloaded conditions show iHss around 1 µA/cm2 and hydrogen diffusion coefficients around 7·10-12 m2/s. Such values are comparable to literature data collected on X65 steels. Preliminary tests under cyclic load show that iP modifies with load, but the response is shifted in phase. The amplitude of ∆iP increases with the load amplitude and frequency. Such behavior can be ascribed to the rupture and reformation of passive film, which is more evident at the highest strain rates (high frequencies). Similar behavior was noticed also for iHss, but values of ∆iHss are of the same order of magnitude of ∆iP. The average value of the hydrogen stationary permeation flux remains almost constant as the load frequency increases
The attractiveness of additive manufacturing (AM) relates to the ability of this technology to ra... more The attractiveness of additive manufacturing (AM) relates to the ability of this technology to rapidly produce very complex components at affordable costs. However, the properties and corrosion behavior, in particular, of products produced by AM technology should at least match the properties obtained by conventional technologies. The present study aims at evaluating the corrosion behavior and corrosion fatigue endurance of AlSi10Mg alloy produced by selective laser melting (SLM) in comparison with its conventional counterpart, gravity cast alloy. The results obtained indicate that the corrosion resistance of the printed and cast alloys was relatively similar, with a minor advantage to the printed alloy. The corrosion fatigue endurance of the printed alloy was relatively improved compared to the cast alloy. This was mainly attributed to the significant differences between the microstructure and defect characteristics of those two alloys.
The paper is devoted to the study of stress corrosion cracking phenomena in friction stir welding... more The paper is devoted to the study of stress corrosion cracking phenomena in friction stir welding AA-2024 T3 joints. Constant load (CL) cell and slow strain rate (SSR) tests were carried out in aerated NaCl 35 g/L solution. During the tests, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were measured in the different zones of the welding. The results evidenced initial practical nobilty of the nugget lower compared to both heat-affected zone and the base metal. This effect can be mainly ascribed to the aluminum matrix depletion in copper, which precipitates in form of copper-rich second phases. In this zones, no stress corrosion cracking was noticed, but well-evident stress-enhanced intergranular corrosion occurred. This is due to the uneven distribution of platic deformation during the slow strain rate tests. Higher strain values are localized at the heat affected zone, where softening occurs. On the contrary, stress values at the nugget are not sufficient to favor both the initiation and propagation of stress corrosion cracks. In the range of processing parameter studied in this experimental work, the stress corrosion cracking susceptibility of the friction stir welding (FSW)-ed alloy is then similar to that of the base metal.
In this paper, synergistic effects of chloride (Cl-) and thiosulfate (S 2 O 3 2-) on corrosion re... more In this paper, synergistic effects of chloride (Cl-) and thiosulfate (S 2 O 3 2-) on corrosion resistance of additively manufactured (AM) and wrought 316L stainless steel (SS) were investigated in ammonium chloride (NH 4 Cl) solution in the absence and presence of different concentrations of sodium thiosulfate (Na 2 S 2 O 3). General corrosion induced by Claccelerated with the increase of S 2 O 3 2concentration for both of the samples. However, pitting resistance of AM 316L SS was found to be at least 4-to 6-fold higher than that of the wrought sample depending on S 2 O 3 2concentration. The AM sample demonstrated significantly improved metastable pitting resistance in the presence of S 2 O 3 2into Clsolution. In addition, the passive film of AM 316L SS offered higher charge transfer resistance and film resistance confirming its better stability and barrier characteristics in Cl-S 2 O 3 2environment. The superior corrosion resistance of AM 316 L SS compared to wrought sample was attributed to refined microstructure, absence of MnS micro-inclusions, and lack of Cr depleted regions.
This paper deals with variability in the performance of seven different superplasticizers that we... more This paper deals with variability in the performance of seven different superplasticizers that were chosen among those of most common use belonging to the naphthalene (NSF) and polycarboxylate-based (PCE) families. In particular, compatibility of two naphthalene-based and five polycarboxylate-based admixtures with six different cements available on the Italian market was evaluated by measuring water reduction to manufacture mortars with the same workability at the end of mixing. Two different lots of the same cement (same plant) were used: lot 1 and 2 produced, on September 2005 and March 2006 respectively. Flow attention up to sixty minutes and tendency to entrap air in the mortars were measured. Results confirmed that the average water reduction and flow retention properties are better for PCE compare to NSF superplasticizers. However, experimental data confirm as the performance of PCE admixtures are more strongly dependent on the cement type than those of NSF polymers. No differences were detected in terms of the air entrapped between the two superplasticizer families, except for the ACR(5) superplasticizer.
The paper deals with the effect of heat treatments on corrosion resistance of an AlSilOMg alloy o... more The paper deals with the effect of heat treatments on corrosion resistance of an AlSilOMg alloy obtained by means of Direct Metal Laser Sintering. The tests were performed on as-processed alloy and after different post-heat treatment, covering stress relieving, annealing at high temperature and water quenching. Potentiodynamic and electrochemical impedance spectroscopy tests were carried out in aerated Harrison solution. The results show localized corrosion and selective penetrating attack at the border of melt pools on untreated or only stress relieved specimens. The selective attack was not observed after high temperature annealing. Modification of EIS plot evidenced galvanic coupling with silicon coarse particles that extensively precipitate during high temperature annealing. The morphology of precipitates is described in order to evidence their relevance in terms of rising selective penetrating attack and galvanic coupling.
The present study was carried out to evaluate how the process parameters affect the mechanical pr... more The present study was carried out to evaluate how the process parameters affect the mechanical properties and the corrosion behavior of joints obtained by friction stir welding (FSW). The experimental study was performed by means of a CNC machine tool for the friction stir welding of two aluminum alloys, namely AA7075 and AA2024, taking also into account the combination between the two materials. The joints were executed varying the process parameters, namely rotational speed and feed rate. Tensile tests and hardness tests were carried out to evaluate the mechanical properties of the joints. The corrosion behavior of welded specimens was analyzed by means of local free corrosion potential measurements to determine anodic and cathodic areas of welds. The results evidenced that the low hardness areas have the free corrosion potential more anodic than the nearest zones. The differences of potential between the different areas of the welding have the consequence of galvanic corrosion of the less noble area. The location and the extension of the anodic areas depend both on the alloy and on the welding parameters. The preferentially corrosion of these areas were confirmed by means of long time immersion tests. The attacks morphology depends on the alloy: in AA2024 a severe crevice and pitting attack takes place, whereas the AA7075 shows exfoliation corrosion along the rolling bands. Coupling the two different alloys, a severe galvanic attack takes place on the AA7075, in the correspondence of the lower hardness areas. The decreasing of hardness and the different electrochemical behavior in the correspondence of the welding were due to the microstructural alteration of the alloys during the FSW. The correlation between process parameters and joints properties allowed to identify the most suitable welding conditions.
The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-co... more The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-compressing structures can promote localized attacks as a function of pH. The aggressive local environment in the occluded cells inside localized attacks has as consequence the possibility of initiation of stress corrosion cracking. In this paper, the stress corrosion cracking behavior of high strength steels proposed for tendons was studied by means of Constant Load (CL) tests and Slow Strain Rate (SSR) tests. Critical ranges of pH for cracking were verified. The promoting role of localized attack was confirmed. Further, electrochemical tests were performed on bars in as received surface conditions, in order to evaluate pitting initiation. The adverse effect of mill scale was recognized.
Calcium chloride is one of the main de-icing salts for removing snow and ice from roads, infrastr... more Calcium chloride is one of the main de-icing salts for removing snow and ice from roads, infrastructures and service areas. It is well known that reinforced concrete structures, if exposed to calcium chloride, can suffer from severe damages due to both corrosion of steel reinforcement and chemical attack of the cement paste. This paper aims at evaluating the resistance to chemical attack of mortars manufactured with different low-carbon binders (alkali activated slag cements, calcium sulphoaluminate cement-based blends, high volume ultrafine fly ashes cements) in presence of CaCl2-based de-icing salts in cold weather (temperature about 4°C). Results indicated that alkali activated slag-based mortars are quasi-immune to calcium chloride attack due to their mineralogical composition. On the contrary, calcium sulphoaluminate-based blends show the total loss of binding capacity, especially when calcium sulphoaluminate cement is used with gypsum and Portland cement. Finally, the partial substitution of Portland cement with ultrafine fly ash strongly reduces the mass change and the strength loss of mortars submerged in 30 wt.% CaCl2 solutions due to the strong reduction of calcium hydroxide responsible for the calcium oxychloride formation in the cement paste.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The paper reports the results of an experimental work on the effect of steel microstructures on m... more The paper reports the results of an experimental work on the effect of steel microstructures on morphology and protectiveness of the corrosion scale formed in water saturated by supercritical CO 2. Two HSLA steels were tested. The microstructures were modified by means of different heat treatments. Weight loss was measured after exposure at CO 2 partial pressure of 80 bar and 60 ∘ C temperature. The morphology of the scale was analyzed by means of scanning electron microscope (SEM) energy-dispersive X-ray spectroscopy (EDX). Cathodic potentiodynamic tests were carried out on precorroded specimens for evaluating the effect of preformed scales on cathodic polarization curves in CO 2 saturated sulphuric acid solution at pH 3, which is the value estimated for water saturated by supercritical CO 2. The results are discussed in order to evaluate the effect of iron carbide network on scale growth and corrosion rate. Weight loss tests evidenced average corrosion rate values in the range 1-2.5 mm/y after 150-hour exposure. The presence of thick siderite scale significantly reduces the corrosion rate of carbon steel. A slight decrease of the corrosion rate was observed as the scale thickness increases and moving from martensite to microstructures containing carbides.
perform their role through three main components: a biocompatible scaffold, cellular component an... more perform their role through three main components: a biocompatible scaffold, cellular component and bioactive molecules. Nanotechnology, using advanced manufacturing techniques such as conventional and unconventional lithography, allows fabricating supports with geometries, sizes and displaying physical chemical properties tuneable over different length scales. In this work we report the fabrication of scaffolds made of fibrin gel and squid pen chitin, for the regeneration of tissues. Materials and methods: Fibrin gel films are used to observe the growth of cells on random networks. Films of different thickness have been fabricated with special attention to the realization of a micro-frame that allows a simple manipulation of the structure. Such a standing fibrin scaffold prevents the artefacts arising from the interaction of the films with other surfaces. The fibrin gel clots have then been stretched to observe if the cells growth and migration is influenced by the orientation of the fibers. Fabricating a scaffold via bottom-up techniques to mimic tissues is not simple. We have chosen to adopt a top-down strategy using a scaffold manufactured by nature and composed of extremely ordered chitin fibers: squid pen. The squid's pen is a support consisting of chitin fibers transparent, biocompatible, low cost and displaying high mechanical resistance. We have changed the chemical and physical properties of the scaffold to promote cell adhesion. Both supports were functionalized with retinoic acid to obtain a support able to induce cell differentiation. We characterized the scaffolds by scanning electron microscopy and immunofluorescence technique. Results: We have fabricated two types of scaffolds and we have observed cell growth on both scaffolds. We fabricated active scaffolds able to differentiate the stem cells into neuronal cells. The ultrastructure characterization of the scaffolds is crucial for evaluating their morphology, porosity and biological efficacy. Power spectrum analyses of the images have been performed to provide the characteristic lengths of the supports. Discussion: An important goal of this work was the fabrication of 3D scaffolds with a well-defined morphology to be used as a starting point for the regeneration of portions of tissue. The realization of a fibrin scaffold, of different thickness and easy to handle fabricated under controlled spatial confinement has been demonstrated. Characterization of the fibrin network has helped us to understand how the morphology of fibrin network might affect the cell growth. We propose the squid pen as a scaffold because it is biocompatible, transparent, it withstands surgical sutures and, moreover, it is a waste material of the industrial chain. The purpose is to exploit as much as possible the original remarkable properties provided by the structure of squid pen chitin to obtain a scaffold transparent and able to support all the mechanical stress. Furthermore, in a period characterized by the necessity of producing goods by a sustainable chemistry and a green economy, finding the way for using an available natural biomass has become a must for all scientists and industrial manufacturers.
Introduction: Pipelines and offshore applications, operating under cathodic protection to prevent... more Introduction: Pipelines and offshore applications, operating under cathodic protection to prevent general corrosion, are usually realized with High Strength Low Alloy (HSLA) steels. The risk of hydrogen embrittlement (HE) in pipeline steels due to cathodic overprotection are described in literature. HE is related to absorption and subsequent diffusion of atomic hydrogen through the lattice. On HSLA steels, HE occurs only in dynamic load conditions in the plastic field, such as slow strain rate or corrosion fatigue. Many studies were carried out on the effect of applied stress on hydrogen diffusion and HE mechanism but, at present, the phenomena are not fully understood. In this work, the effect of cyclic load in the elastic field on passivity current (iP) and hydrogen steady state permeation current (iHss) is reported. Materials and Methods: The permeation tests were carried out on API 5L X65 steel, according to ISO 17081:2014. The specimen acts as bi-electrode between the two compartments of the Devanathan-Stachurski cell. In the anodic compartment, it is polarized at +340 mV vs Ag/AgCl in a 0.1 M NaOH solution. The cathodic compartment is filled with a borate solution (pH 8.5) and a cathodic current density of 2 mA/cm2 was applied once passivity current reached values below 0.05 µA/cm2. Tests in unloaded conditions and under cycling load up to 80% TYS in the frequency range between 10-2 Hz and 1 Hz were performed. Results and Discussion: Tests realized in unloaded conditions show iHss around 1 µA/cm2 and hydrogen diffusion coefficients around 7·10-12 m2/s. Such values are comparable to literature data collected on X65 steels. Preliminary tests under cyclic load show that iP modifies with load, but the response is shifted in phase. The amplitude of ∆iP increases with the load amplitude and frequency. Such behavior can be ascribed to the rupture and reformation of passive film, which is more evident at the highest strain rates (high frequencies). Similar behavior was noticed also for iHss, but values of ∆iHss are of the same order of magnitude of ∆iP. The average value of the hydrogen stationary permeation flux remains almost constant as the load frequency increases
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