A study on corrosion resistance of ISO 5832-1 austenitic stainless steel used as orthopedic implant

The ISO 5832-1 austenitic stainless steel used as biomaterial is largely applied in the area of orthopedics, especially in the manufacture of implants, such as temporary or permanent replacement of bone structures. The objective of this study was to evaluate the localized corrosion resistance of the ISO 5832-1 stainless steel used in orthopedic implants by electrochemical tests in two different solutions. The results of this study are of great interest to evaluate the corrosion of metallic implants that can result in the release of corrosion products into bodily fluids causing possible adverse biological reactions. The determination of the chemical elements in the composition of the ISO 5832-1 stainless steel was performed by neutron activation analysis (NAA). The samples for electrochemical tests were grinded with silicon carbide paper up to #4000 finishing, followed by mechanical polishing with diamond paste. The open circuit potential measurements and anodic polarization curves were obtained in solution of 0.90 wt. % of NaCl and of simulated body fluid (SBF). The results indicated that the ISO 5832-1 stainless steel presented a high resistance to crevice corrosion in simulated body fluid solution but high susceptibility to this form of corrosion in the chloride solution. &nbsp

Study of ph effect on AZ31 magnesium alloy corrosion for using in temporary implants

Currently, magnesium alloys are gaining great interest for medical applications due to their degrading properties in the human body ensuring a great biocompatibility. These alloys also provide profitable mechanical properties due similarities with human bone.  However, a difficulty in applying these materials in the biomaterials industries is the corrosion prior to cell healing. The effect of the chemical composition of Mg alloys on their corrosion behavior is well known. In this study, samples of AZ31 magnesium alloy were cut into chips for elemental chemical analysis by neutron activation analysis (NAA). Concentrations of the elements As, La, Mg, Mn, Na, Sb and Zn were determined in the AZ31 alloy. Visualization tests of agar corrosion development in various media, of 0.90% sodium chloride solution (mass), phosphate buffer saline (PBS) and simulated body fluid (SBF) were performed. Visualizations of the effect of agar gel corrosion revealed pH variation during the corrosion process due to the released into the cathode. The highest released of hydroxyl ions occurred in NaCl solution compared to PBS and SBF solutions indicating that NaCl solution was much more aggressive to the alloy compared to the others

Characterization and determination of the gamma radiation attenuation coefficient in the W20Cu3Ni metallic alloy to be applied in the transport of radioactive substances

The final responsibility of civil society protection regarding the nuclear sector in every country is a local/national governmental duty. The way this task is wielded changes little from country to country. The principal concern is to reduce the exposure of people to sources that eventually emit radiation. The shield used for this purpose is called biological shielding. The W20Cu3Ni metallic alloy was obtained using W powder as a matrix and the infiltrating elements Cu and Ni and subjected to sintering processes at different temperatures. All samples were analyzed by X-ray diffractometry, scanning electron microscopy (SEM). The main objective of this work is to determine the gamma radiation attenuation coefficients of the W20Cu3Ni metallic alloy subjected to different sintering temperatures. The determination of the alloy attenuation coefficient was performed using an experiment set up with a source of cobalt (Co-60), which emits characteristic energy peaks of 1.173 MeV and 1.332 MeV. The gamma rays are focused to reach the detector and the resulting photons are counted for 1800 s in three situations. Initially, the gamma rays are directed to the detector in a free path. The second experiment consists of using pure tungsten to shield the radiation, i.e., all gamma rays have to pass through it before entering the detector. Finally, the metallic alloy replaces tungsten, and the same measurements are done. Despite the amount of copper and nickel present in the final sample, the results obtained for this new metallic alloy are very satisfactory. The measurements of the gamma attenuation coefficient in the W20Cu3Ni metallic alloy at different temperatures, showed significant results, ie, a difference between 7.08% and 14.63% lower than the attenuation coefficient of pure tungsten used as a reference. Therefore, this new W20Cu3Ni metal alloy has excellent potential for application in shielding systems and in the transport of substances with high nuclear activity used in the production of radioisotopes and radiopharmaceuticals