ABSTRACT The facilities designed for the peaceful activities of nuclear energy are made with different materials, among them, reinforced concrete. This material, in addition to being structural, is a barrier for isolation and confinement from the environment of the radioactive materials. One of its degradation mechanisms is the corrosion of the reinforcement, a frequent cause of premature failure in service. Consequently, it is essential to study this degradation mechanism in formulations developed for this purpose, as well as the development and implementation of monitoring techniques. The objective of this work is to compare, from the corrosion of reinforcement point of view, two concrete formulations, one made with ordinary portland cement and the other with pozzolanic portland cement. Both formulations are candidate for some nuclear applications, such as the Low Radioactive Waste disposal facilities, whose durability requirement is higher than 300 years. The results of approximately four years of monitoring are presented. The parameters followed are: corrosion potential and corrosion rate of the reinforcements, electrical resistivity, oxygen flow, internal temperature and carbonation rate of concrete. These parameters were measured and monitored in reinforced concrete specimens by embedded sensors previously developed in our laboratory. Also, unreinforced specimens were prepared to measure the carbonation rate. The presence of reinforcements provides the possibility of monitoring directly on them the corrosion potential, the corrosion rate and electrical resistivity of concrete, using on-surface electrodes provided by a commercial instrument. This allows the comparison of the parameters monitored by embedded sensors and the on-surface electrodes.

Pure titanium or titanium alloys, and to a lesser extent, zirconium, are metals that are often used in direct contact with host tissues. These metallic biomaterials are highly reactive, and on exposure to fluid media or air, quickly develop a layer of titanium dioxide (TiO2) or zirconium dioxide (ZrO2). This layer of dioxide forms a boundary at the interface between the biological medium and the metal structure, determining the degree of biocompatibility and the biological response of the implant. Corrosion is the deterioration a metal undergoes as a result of the surrounding medium (electrochemical attack), which causes the release of ions into the microenvironment. No metal or alloy is entirely inert in vivo. Corrosion phenomena at the interface are particularly important in the evolution of both dental and orthopedic implants and one of the possible causes of implant failure after initial success. This paper comprises a review of literature and presents results of our laboratory experiments related to the study of corrosion, with special emphasis on dental implants. In situ degradation of a metallic implant is undesirable because it alters the structural integrity of the implant. The issue of corrosion is not limited to a local problem because the particles produced as a result could migrate to distant sites, whose evolution would require further studies.

El titanio puro o en aleacion, y en menor grado el circonio, son los metales mas utilizados en contacto directo con los tejidos del huésped. Estos biomateriales metálicos son muy reactivos y al exponerse a medios líquidos o al aire, desarrollan rápidamente una capa de dióxido de titanio (TiO2) o de dioxido de circonio (ZrO2). Esta capa de dióxido limita la interfase entre el medio biológico y la estructura metalica, determinando el grado de biocompatibilidad y la respuesta biológica del implante. La corrosión es el deterioro que sufre un metal debido al medio que lo rodea (ataque electroquímico) y que produce como consecuencia la liberación de iones en el microambiente. In vivo ningun metal o aleacion es completamente inerte. Los fenómenos de corrosión, en la zona de la interfase, son de especial importancia en la evolución de los implantes tanto odontológicos como ortopédicos y constituyen una de las posibles causas de fracaso de un implante luego del éxito inicial. El presente trabajo comprende una revision bibliográfica y la presentación de resultados de las experiencias de nuestro laboratorio en relación al estudio de la corrosión con especial énfasis en los implantes odontológicos. La degradación “in situ” de un implante metálico es un hecho no deseable ya que altera la integridad estructural del implante. La problemática de la corrosión no se limitaría a un problema local dado que las partículas resultantes de este proceso podrían migrar a sitios alejados al sitio del implante, cuya evolución plantea interrogantes para futuros estudios.