Abstract: New interest in magnesium alloys as temporary biomaterials was reborn in the recent years. Especially metals based on physiological trace elements seem to be promising as an alternative to current biodegradable implant materials in cardiovascular and musculoskeletal applications. First clinical reports can be dated back before 1900. Magnesium alloys were used by surgeons of different clinical background in cardiovascular, neural, skin, general and musculoskeletal surgery. All patients have benefited from the treatment with magnesium alloys, although rapid corrosion caused sometimes painless subcutaneous gas cavities. These reports encouraged researchers to study and invent new magnesium alloys which aim to provide more uniform and slow corrosion rates. The most challenging part was to analyze the corrosion of implanted magnesium alloys in-vivo, since the magnesium alloys interlock with the surrounding tissue during corrosion. Therefore, the implanted samples could not be retrieved without damaging the fragile implant-tissue interface. Synchrotron-radiation based microtomography (SRµCT) was introduced as a solution to this challenge. SRµCT enables to measure non-destructively the in-vivo corrosion rates of magnesium alloys as well as their corrosion morphology. Based on these data, it was concluded that suitable magnesium implants should provide small grains, which are distributed very homogenously and should be produced with highest purity. The future of biodegradable magnesium alloys might be directed towards implant areas where high ductility, maximal tensile strength as well as high compression strength is needed and the properties of current biodegradable implant-materials are exceeded by the properties of magnesium alloys.
Abstract: In last years there is paid a special attention to the analytical chemistry of platinic metals
(rhutenium, osmium, platinum, iridium, palladium, rhodium), due to increasing concerns on
recovery and recirculation of these metals, especially platinum. In this context, recent data of
specialty literature, regarding the approach of new methodological and chemical techniques in
platinum metals determination from a variety of complex matrices and wide ranges of
concentrations are systematized and briefly discussed.
Abstract: High rates of degradation in corrosive media represent the Achilles heel of Mg alloys, which hinders their applications in various areas, particularly in prosthetics. We present an investigation of the degradation behavior of magnesium alloy AZ91D and AM50 in different solutions that simulates bodily fluids. The degradation rate is shown to be significantly reduced by different Al contents in the alloy. Furthermore, the corrosive solutions containing protein influenced on the oxidation behavior of the studied alloys
Abstract: This paper summarizes the results of various attempts to implement a neural network for solving corrosion problems.
The first activity was aimed to develop a model able to predict crevice corrosion of stainless steel and related alloys in chloride containing media from long-term exposure tests.
Second, the preliminary evaluation of a neural network approach for rapid prediction of naphthenic acid corrosion performance (NAC) of carbon and stainless steels in a crude oil distillation unit will be described. In this work, the neural network was trained on the basis of experimental data from laboratory experience.
Finally, non-deterministic models based on artificial neural network (ANN) were developed to predict the corrosion rate of carbon steel in CO2 environment by elaborating laboratory and field data. NN models were developed and tested using, as an input, pattern physico-chemical variables typically met in empiric and mechanistic models as well as parameters apparently not involved in the corrosion phenomenon. Results confirmed the validity of the NN approach
Abstract: Desalination is a viable solution to the 21th century´s shortage of freshwater. The most widely used desalination processes are thermal and membrane. Other modern techniques apply solar and electrical energy for evaporation and electrodialysis. Many desalination plants (DP) are located in desertic/arid regions with a harsh climate and limited rainfall. About one-fifth of the DPs operate in the Middle East, with Saudi Arabia producing half of the world desalted water. The final selection of materials of construction for plant equipment must be a compromise between technological and economic factors. Corrosion problems and their solutions in several DPs in the Middle East, USA and Mexico are presented.
Abstract: There is a deep universal concern today about the influence of pollutants on the environment including soil, air and in particular water, and about their effects on the durability of engineering materials and the deterioration of structures and the infrastructure. Water pollutants affect the terrestrial, atmospheric and aquatic environments, and even when present at very low levels of a few ppm may impair human health, aquatic life and water quality. The avoidance of water pollution is, therefore, an important part of water resource management. The present work provides an overview of the effects of hydrogen sulfide (H2S) on corrosion in polluted waters, including sea, river, brackish, geothermal and sewage waters.
Abstract: Arc welds were made on wrought AZ31 magnesium plate using a variable polarity gas-tungsten arc process with AZ61 filler wire. The aluminum content of the weld metal was systematically varied using inserts pre-placed in the weld joint, machined from magnesium die-cast alloys AM20, AM50, AM60, and AZ91. When immersed in 3.5% NaCl + Mg(OH)2 solution at room temperature, pitting corrosion was found to initiate in the weld heat affected zone, spread briefly to the weld metal, and then concentrate in the base metal. Galvanic couples were examined between wrought AZ31 and die-cast alloys to further examine galvanic behavior between wrought and cast materials. Results showed that the cast material was anodic relative to the wrought material over long periods of time, unlike what was observed for weldments. Details of this study will be presented and results will be related to alloy aluminum content and the ability to passivate.