Publicación: Corrosión de cobre y magnesio en fluidos biológicos
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Comisión Nacional de Energía Atómica. Instituto de Tecnología Sabato
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Tesis para optar al título de Magister en Ciencia y Tecnología de Materiales
En el presente trabajo se ha estudiado la corrosión de dos materiales metálicos potencialmente útiles como materiales implantables degradables: el cobre y la aleación de magnesio AZ31. El cobre es el constituyente principal de uno de los tipos de dispositivos intrauterinos [DIU]. Su efecto anticonceptivo se atribuye a los iones cobre liberados como resultado de la corrosión del alambre de cobre en el útero. La vida útil del DIU se calcula en base a la velocidad de disolución del cobre y da como resultado varios años de utilidad. Sin embargo, existen referencias de que la corrosión podría llevar a la ruptura o fragmentación del alambre luego de un corto período de uso. Por ese motivo en este trabajo se investigó la susceptibilidad del alambre de cobre a la corrosión bajo tensión [CBT] en medios que simulan fluidos uterinos y se analizó el efecto de los componentes de dichos medios sobre el proceso de corrosión del cobre. Se concluyó que el cobre no es susceptible a la CBT en el fluido uterino simulado. La ruptura de los alambres in utero que conduciría a la falla prematura del dispositivo estaría relacionada con la reducción de la sección transversal provocada por la corrosión generalizada y no por la CBT. En base a los resultados obtenidos se planteó un mecanismo de reacción que contempla la formación de compuestos adsorbidos como la urea y compuestos que contienen cloruros, así como la oxidación de los iones Cu[I] a Cu[II] en solución. Las aleaciones de magnesio son potencialmente útiles como biomateriales para aplicaciones ortopédicas de osteosíntesis. Sin embargo, su velocidad de corrosión es demasiado alta. Por lo tanto, es necesario un estudio del comportamiento electroquímico de estas aleaciones in Vitro como primer paso para mejorar su resistencia a la corrosión. A tal fin se realizaron ensayos de polarización potenciodinámicas en soluciones que simulan fluidos biológicos y se analizó el efecto de la composición de los mismos en el proceso de degradación de la aleación de magnesio monofásica AZ31 con dos tratamiento termomecánicos diferentes. Los resultados mostraron que la aleación AZ31 sufre corrosión por picado en medios que contienen cloruros y que el mecanismo de disolución es afectado por la presencia de los distintos componentes de los fluidos biológicos tales como cloruros, fosfatos y proteínas [albúmina]. En presencia de ambos iones el efecto de la albúmina varía con la microestructura de aleación y depende de la concentración de la misma en solución. Se observó también que las partículas intermetálicas constituirían zonas catódicas sobre las cuales se llevaría a cabo la reacción de evolución de hidrógeno, impidiendo la precipitación de los fosfatos de magnesio alrededor de las mismas y generando sitios preferenciales para el comienzo de la corrosión localizada. Los estudios realizados con ambos materiales pusieron en relieve la complejidad de los mecanismos de corrosión de metales implantables en fluidos biológicos que dependen tanto de la composición de estos últimos como de la microestructura de los metales y de los fenómenos de transporte de materia en la interfase.|In the present work the corrosion of two Metallica materials, copper and AZ31 magnesium alloy, potentially useful as degradable implant materials, was studied. Copper is the main component of a type of intrauterine devices [IUD]. Its contraceptive effect is attributed to the copper ions released as a result of the corrosion of the copper wire in the uterus. The service life of the IUD is calculated on the basis of the dissolution rate of copper and results in several years of utility. Nevertheless, it was reported that corrosion could lead to the breakdown or fragmentation of the wire after a short period of use. In the present work the susceptibility of the copper wire to stress corrosion cracking [SCC] in simulated uterine fluids was investigated and the effect of the components of these fluids on copper corrosion was analyzed. It was demonstrated that copper is not susceptible to SCC in the simulated uterine fluid. The breakdown of the wires in the uterus that would result in the premature failure of the device would be related to the reduction of the cross section induced by the general corrosion but should not be associated to SCC. On the basis of the corrosion results a reaction mechanism that includes the formation of adsorbed species such urea and chlorides-containing products and the oxidation of Cu[I] to Cu[II] in the solution is presented. Magnesium alloys are potentially useful as biomaterials for orthopedic applications. However, its corrosion rate is too high. Consequently, the study of the electrochemical behavior of these alloys is necessary as a first step to improve their corrosion resistance. With this purpose, potentiodynamic polarization tests in solutions that simulate biological fluids were performed and the effect of the components of biological fluids on the degradation process of the single-phase magnesium alloy Az31 with two different termomechanical processing was analyzed. Results showed that AZ31 experienced pitting corrosion in chloride-containing media and that the dissolution mechanism is affected by some of the components of the biological fluids such as chlorides, phosphates and proteins [albumin]. In the presence of both anions the effect of albumin depends on the microstructure of the alloy. It was also shown that the precipitates would constitute cathode zones where hydrogen evolves, hindering the precipitation of magnesium phosphates and generating preferential sited for localized corrosion. Present results reveal the complexity of the corrosion mechanisms of implantable materials in biological fluids, which depend on the composition of these fluids, on the microstructure of the metals and on mass transport phenomena at the interface.
In the present work the corrosion of two Metallica materials, copper and AZ31 magnesium alloy, potentially useful as degradable implant materials, was studied. Copper is the main component of a type of intrauterine devices [IUD]. Its contraceptive effect is attributed to the copper ions released as a result of the corrosion of the copper wire in the uterus. The service life of the IUD is calculated on the basis of the dissolution rate of copper and results in several years of utility. Nevertheless, it was reported that corrosion could lead to the breakdown or fragmentation of the wire after a short period of use. In the present work the susceptibility of the copper wire to stress corrosion cracking [SCC] in simulated uterine fluids was investigated and the effect of the components of these fluids on copper corrosion was analyzed. It was demonstrated that copper is not susceptible to SCC in the simulated uterine fluid. The breakdown of the wires in the uterus that would result in the premature failure of the device would be related to the reduction of the cross section induced by the general corrosion but should not be associated to SCC. On the basis of the corrosion results a reaction mechanism that includes the formation of adsorbed species such urea and chlorides-containing products and the oxidation of Cu[I] to Cu[II] in the solution is presented. Magnesium alloys are potentially useful as biomaterials for orthopedic applications. However, its corrosion rate is too high. Consequently, the study of the electrochemical behavior of these alloys is necessary as a first step to improve their corrosion resistance. With this purpose, potentiodynamic polarization tests in solutions that simulate biological fluids were performed and the effect of the components of biological fluids on the degradation process of the single-phase magnesium alloy Az31 with two different termomechanical processing was analyzed. Results showed that AZ31 experienced pitting corrosion in chloride-containing media and that the dissolution mechanism is affected by some of the components of the biological fluids such as chlorides, phosphates and proteins [albumin]. In the presence of both anions the effect of albumin depends on the microstructure of the alloy. It was also shown that the precipitates would constitute cathode zones where hydrogen evolves, hindering the precipitation of magnesium phosphates and generating preferential sited for localized corrosion. Present results reveal the complexity of the corrosion mechanisms of implantable materials in biological fluids, which depend on the composition of these fluids, on the microstructure of the metals and on mass transport phenomena at the interface.
En el presente trabajo se ha estudiado la corrosión de dos materiales metálicos potencialmente útiles como materiales implantables degradables: el cobre y la aleación de magnesio AZ31. El cobre es el constituyente principal de uno de los tipos de dispositivos intrauterinos [DIU]. Su efecto anticonceptivo se atribuye a los iones cobre liberados como resultado de la corrosión del alambre de cobre en el útero. La vida útil del DIU se calcula en base a la velocidad de disolución del cobre y da como resultado varios años de utilidad. Sin embargo, existen referencias de que la corrosión podría llevar a la ruptura o fragmentación del alambre luego de un corto período de uso. Por ese motivo en este trabajo se investigó la susceptibilidad del alambre de cobre a la corrosión bajo tensión [CBT] en medios que simulan fluidos uterinos y se analizó el efecto de los componentes de dichos medios sobre el proceso de corrosión del cobre. Se concluyó que el cobre no es susceptible a la CBT en el fluido uterino simulado. La ruptura de los alambres in utero que conduciría a la falla prematura del dispositivo estaría relacionada con la reducción de la sección transversal provocada por la corrosión generalizada y no por la CBT. En base a los resultados obtenidos se planteó un mecanismo de reacción que contempla la formación de compuestos adsorbidos como la urea y compuestos que contienen cloruros, así como la oxidación de los iones Cu[I] a Cu[II] en solución. Las aleaciones de magnesio son potencialmente útiles como biomateriales para aplicaciones ortopédicas de osteosíntesis. Sin embargo, su velocidad de corrosión es demasiado alta. Por lo tanto, es necesario un estudio del comportamiento electroquímico de estas aleaciones in Vitro como primer paso para mejorar su resistencia a la corrosión. A tal fin se realizaron ensayos de polarización potenciodinámicas en soluciones que simulan fluidos biológicos y se analizó el efecto de la composición de los mismos en el proceso de degradación de la aleación de magnesio monofásica AZ31 con dos tratamiento termomecánicos diferentes. Los resultados mostraron que la aleación AZ31 sufre corrosión por picado en medios que contienen cloruros y que el mecanismo de disolución es afectado por la presencia de los distintos componentes de los fluidos biológicos tales como cloruros, fosfatos y proteínas [albúmina]. En presencia de ambos iones el efecto de la albúmina varía con la microestructura de aleación y depende de la concentración de la misma en solución. Se observó también que las partículas intermetálicas constituirían zonas catódicas sobre las cuales se llevaría a cabo la reacción de evolución de hidrógeno, impidiendo la precipitación de los fosfatos de magnesio alrededor de las mismas y generando sitios preferenciales para el comienzo de la corrosión localizada. Los estudios realizados con ambos materiales pusieron en relieve la complejidad de los mecanismos de corrosión de metales implantables en fluidos biológicos que dependen tanto de la composición de estos últimos como de la microestructura de los metales y de los fenómenos de transporte de materia en la interfase.|In the present work the corrosion of two Metallica materials, copper and AZ31 magnesium alloy, potentially useful as degradable implant materials, was studied. Copper is the main component of a type of intrauterine devices [IUD]. Its contraceptive effect is attributed to the copper ions released as a result of the corrosion of the copper wire in the uterus. The service life of the IUD is calculated on the basis of the dissolution rate of copper and results in several years of utility. Nevertheless, it was reported that corrosion could lead to the breakdown or fragmentation of the wire after a short period of use. In the present work the susceptibility of the copper wire to stress corrosion cracking [SCC] in simulated uterine fluids was investigated and the effect of the components of these fluids on copper corrosion was analyzed. It was demonstrated that copper is not susceptible to SCC in the simulated uterine fluid. The breakdown of the wires in the uterus that would result in the premature failure of the device would be related to the reduction of the cross section induced by the general corrosion but should not be associated to SCC. On the basis of the corrosion results a reaction mechanism that includes the formation of adsorbed species such urea and chlorides-containing products and the oxidation of Cu[I] to Cu[II] in the solution is presented. Magnesium alloys are potentially useful as biomaterials for orthopedic applications. However, its corrosion rate is too high. Consequently, the study of the electrochemical behavior of these alloys is necessary as a first step to improve their corrosion resistance. With this purpose, potentiodynamic polarization tests in solutions that simulate biological fluids were performed and the effect of the components of biological fluids on the degradation process of the single-phase magnesium alloy Az31 with two different termomechanical processing was analyzed. Results showed that AZ31 experienced pitting corrosion in chloride-containing media and that the dissolution mechanism is affected by some of the components of the biological fluids such as chlorides, phosphates and proteins [albumin]. In the presence of both anions the effect of albumin depends on the microstructure of the alloy. It was also shown that the precipitates would constitute cathode zones where hydrogen evolves, hindering the precipitation of magnesium phosphates and generating preferential sited for localized corrosion. Present results reveal the complexity of the corrosion mechanisms of implantable materials in biological fluids, which depend on the composition of these fluids, on the microstructure of the metals and on mass transport phenomena at the interface.
In the present work the corrosion of two Metallica materials, copper and AZ31 magnesium alloy, potentially useful as degradable implant materials, was studied. Copper is the main component of a type of intrauterine devices [IUD]. Its contraceptive effect is attributed to the copper ions released as a result of the corrosion of the copper wire in the uterus. The service life of the IUD is calculated on the basis of the dissolution rate of copper and results in several years of utility. Nevertheless, it was reported that corrosion could lead to the breakdown or fragmentation of the wire after a short period of use. In the present work the susceptibility of the copper wire to stress corrosion cracking [SCC] in simulated uterine fluids was investigated and the effect of the components of these fluids on copper corrosion was analyzed. It was demonstrated that copper is not susceptible to SCC in the simulated uterine fluid. The breakdown of the wires in the uterus that would result in the premature failure of the device would be related to the reduction of the cross section induced by the general corrosion but should not be associated to SCC. On the basis of the corrosion results a reaction mechanism that includes the formation of adsorbed species such urea and chlorides-containing products and the oxidation of Cu[I] to Cu[II] in the solution is presented. Magnesium alloys are potentially useful as biomaterials for orthopedic applications. However, its corrosion rate is too high. Consequently, the study of the electrochemical behavior of these alloys is necessary as a first step to improve their corrosion resistance. With this purpose, potentiodynamic polarization tests in solutions that simulate biological fluids were performed and the effect of the components of biological fluids on the degradation process of the single-phase magnesium alloy Az31 with two different termomechanical processing was analyzed. Results showed that AZ31 experienced pitting corrosion in chloride-containing media and that the dissolution mechanism is affected by some of the components of the biological fluids such as chlorides, phosphates and proteins [albumin]. In the presence of both anions the effect of albumin depends on the microstructure of the alloy. It was also shown that the precipitates would constitute cathode zones where hydrogen evolves, hindering the precipitation of magnesium phosphates and generating preferential sited for localized corrosion. Present results reveal the complexity of the corrosion mechanisms of implantable materials in biological fluids, which depend on the composition of these fluids, on the microstructure of the metals and on mass transport phenomena at the interface.