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The blasting process to increase the roughness of the surface of metallic biomaterials is widely used. As a consequence, one can produce a renewed surface with different topography and chemical composition compared to the original one, which can alter the general corrosion behaviour of the samples. With this idea, the aim of this work is not only the topographical and compositional characterization of blasted surfaces of Ti6Al4V alloy but mainly its influence on the corrosion behaviour of these modified surfaces. The surfaces of Ti6Al4V alloys were blasted with SiO2/ZrO2 and Al2O3 particles of different size in order to obtain different roughnesses. To carry out the microstructural and topographical characterization of the blasted surfaces, the scanning electron microscopy (SEM) coupled with an energy dispersive X-ray (EDX), the contact profilometry method and the 3D characterization by means of stereo-Fe-SEM have been used. By means of stereo-Fe-SEM, the roughness and the real surface area of the rough surfaces have been calculated. The microstructural, topographical and compositional results have been correlated with the corrosion behaviour of the samples immersed in Hank's solution and studied by means of electrochemical impedance spectroscopy (EIS). The blasting process alters topographical and chemically the surface of the samples. These modifications induce to an increase in the capacitance values of the roughened samples due to the prevalence of the effect of electrochemically active areas of Ti6Al4V surface over the effect of the presence of Al2O3 and ZrO2 particles on the blasted surfaces. However, the general corrosion behaviour of the samples is not drastically changed. © 2007 Elsevier Ltd. All rights reserved.

The activities concerned with the evaluation, repair and restoration of structures are estimated to amount to 35% of the total volume of the work in the building sector and this continues to increase. The corrosion of rebars in the reinforced concrete structures (RCS) is the main reason for their degradation, so the use of reinforcing stainless steels seems to be one of the possible solutions with most probabilities of solving this problem. In this work, in order to demonstrate the advantages of using reinforcing stainless steels, the corrosion behaviour of AISI 304 and 316 reinforcements embedded in concrete slabs (C35/45 and C60/70 concrete) with two chloride contents are compared with three low-cost and low-Ni austenoferritic stainless steels and with the conventional carbon steel. The lower chloride contamination selected in this research, was enough to cause the corrosion in the active state of the carbon steel reinforcements, whereas the highest one exceeded the expected contamination in the natural environments, including sea media. The metallic materials remaining in the passive state can be considered, from the point of view of corrosion resistance, adequate as reinforcements in the RCS. © 2007 Elsevier Ltd. All rights reserved.

The main problem of the building sector is the limited durability of reinforcing concrete structures under highly aggressive environments due to the corrosion of reinforcements. In order to demonstrate that stainless steels are the adequate solution to avoid corrosion of reinforced concrete structures by contained chlorides, the corrosion behaviour of AISI 304 and AISI 316L stainless steels in mortar with two chloride doses is compared with the corrosion behaviour of three new stainless steels of low Ni content and reduced cost, and with the traditional carbon steel. The lowest chloride contamination (2% Cl-) has been used in this research to provoke corrosion in an active state of reinforcing carbon steel, whereas the highest one (5% Cl-) exceeds all expected levels found in the natural environment, including sea water. The new stainless steels remain in the passive state in mortar specimens with both chloride contents. © 2007 Elsevier Ltd. All rights reserved.

Thermal oxidation treatments of Ti6Al4V, at 500 and 700°C, for 1 h result in the formation of an outer "ceramic" layer of rutile, which enhances osteoblast response. In the present study, we have measured in vitro Ti and Al ion release from Ti64 alloy in the as-received state and after thermal oxidation treatments at 500 or 700°C, to culture medium under standard cell-culture conditions. Concentrations of both Ti and Al released from both thermal oxidation treatments were lower than from polished alloy. Al was released from the treated or untreated surfaces in substantially lower extent than Ti. Titanium and aluminium ions affected primary human osteoblast proliferation, metabolic activity, and differentiation in a dose-dependent manner. Treatments with individual Ti or Al metal ions in similar concentration ranges than released from the surfaces did not alter osteoblast response, which also remained unaffected after treatments with combinations of Ti plus Al applied in the proportional relations than detected in ion-release experiments. We then selected higher concentrations of Ti that impaired osteoblast proliferation and differentiation, while the proportional lower concentrations of Al did not alter osteoblast behavior. In spite of its inert character, it was found that Al significantly enhanced the deleterious effect of Ti on osteoblast differentiation. Therefore, thermal oxidation treatments of Ti6Al4V alloy may improve the biocompatibility of the alloy by reducing both Ti and Al release, and thus attenuating ion-mediated interference with osteoblast differentiation. © 2005 Wiley Periodicals, Inc.

Monitoring benzenesulfonates (BS) and naphthalenesulfonates (NS) took place in five municipal sewage treatment plants (STP). A previously optimized method based on solid phase extraction with polymeric cartridges followed by ion-pair liquid chromatography-electrospray-mass spectrometry (SPE-IPC-ESI-MS) was used. This work confirmed the little or no effect of primary settlement on total organic carbon (TOC) and monosulfonated compounds removal, whereas the main reduction is obtained at the biological stage. However, the most polar compounds, such as naphthalenedisulfonates (NDS), were not effectively removed using the biological treatment. An aromatic sulfonated compound is suggested to be used as a tracer of the origin of industrial pollutants discharged into STPs. A bioluminescence inhibition test, Microtox® assay, allowed toxicity determination of the most relevant aromatic sulfonated compounds detected and toxicity comparison between primary and secondary effluents., Sulphonated organic pollutants enter sewage treatment plants and although they partly discharged into the river waters no toxic effects are observed when biological treatment is used.

Iron aluminides do not generally show good aqueous corrosion resistance. The present study attempts to improve their corrosion resistance by prior surface oxidation. While good corrosion resistance can indeed be obtained, it is found to be difficult to ensure that the oxide layer is continuous and defect free. © 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

In this work, the influence of thermal oxidation treatments of Ti6Al4V at 500°C and 700°C for 1h on the in vitro corrosion behaviour and osteoblast response is studied. The potential of these treatments, aimed to improve the wear surface performance as biomaterial, relies in the formation of an outer >ceramic> layer of rutile. The corrosion behaviour was evaluated in simulated human fluids by electrochemical impedance spectroscopy and anodic polarisation tests. The effect of these thermal oxidation treatments on osteoblastic behaviour was studied in primary cultures of human osteoblastic cells. Results show that thermal oxidation treatments do not decrease the high in vitro corrosion resistance of the Ti6Al4V alloy. Osteoblast adhesion studies indicate that thermal oxidation treatments do not impair the material biocompatibility. Moreover, the thermal oxidation at 700°C enhances the in vitro osteoblastic cell attachment compared to the thermal oxidation at 500°C. © 2002 Published by Elsevier Science Ltd.

The present work analyzes the oxidation kinetics of MA 956 and PM 2000 alloys at 900 and 1100°C for exposure times up to 1000 hr. Special emphasis was placed on a comparison of the alumina-scale integrity formed at 1100°C by means of electrochemical tests at room temperature, which have been shown to be very reliable methods to detect the presence of micro defects within oxide scales. To check whether a preoxidation treatment makes these materials corrosion resistant against aggressive fluids, an electrolyte containing chloride ions was chosen. The mass gain of MA 956 was found to be slightly lower than that of PM 2000 up to 200 hr exposure at 1100°C and for the whole exposure range at 900°C. A subparabolic time dependence (n=0.3) of the oxide growth rate was determined for both alloys at both temperatures. On the other hand, the electrochemical-impedance spectroscopy (EIS) and anodic-polarization tests performed on preoxidized alloys (1100°C/100 hr) revealed good room-temperature corrosion behavior for both alloys, the corrosion resistance and polarization values being somewhat higher for preoxidized PM 2000. Consideration of these results and those of both surface and cross-section examinations of the scale, the better room-temperature corrosion behavior of preoxidized PM 2000 denotes the formation of a denser and mechanically more stable alumina scale containing a lower number of microdefects. This could result from the higher aluminum content of this alloy and the lower density of chemical heterogeneities within the scale. The higher mass gain of PM 2000 could be related to the higher concentration of oxide nodules on top of the alumina scale, as deduced from SEM examination. © 2001 Plenum Publishing Corporation.

The corrosion behaviour of MA 956 in the Hank's solution has been investigated after three different thermal cycles, which lead to hardness values of 250, 289, and 330 HV. The electrochemical tests have shown that the uniform corrosion resistance is independent of the material state. The alloy develops a passive layer on the surface, which provides it with low corrosion rates. The pitting corrosion resistance, however, was seriously affected by the degree of precipitation. Specimens with the lowest and intermediate hardness were able to withstand polarization above 1000 mV, whereas specimens with the higher hardness had a value of 250 mV. We believe that the local differences in Cr concentration associated with the spinodal decomposition, which increase with increasing annealing time at 475°C, could have influenced the characteristics of the passive layer. © 2001 Elsevier Science Ltd. All rights reserved.

In this study the response to corrosion by MA 956 with an alumina layer generated at 1100°C for 100 h considering different modifications of the corrosive medium was evaluated. Possible defects which might exist or be produced in the alumina layer have been also considered. The corrosion resistance was investigated by means of electrochemical impedance spectroscopy (EIS) and anodic polarisation curves. The corrosive medium was Hank's solution with variations in pH and different oxydation level. The alumina/MA 956 system is able to resist changing environment conditions such as variations in pH, and different oxygenation levels without altering its resistance to corrosion. This aids in simulation of hematomas, inflammations, or in vivo infections. © WILEY-VCH Verlag GmbH, 2000.

The corrosion behaviour of an Fe3Al-base intermetallic compound with different crystal structures in a chloride containing solution has been investigated. The corrosion current densities of this intermetallic were independent of the material crystal structure showing a passive state stable with time. These corrosion rates were of the same order of magnitude as for 316L stainless steel. The pitting corrosion resistance evaluated by means of cyclic anodic polarization curves was high for all different states. Amongst the different crystal structures of this intermetallic alloy, the two ordered states present the lowest pitting probability. This Fe3Al intermetallic shows higher pitting corrosion resistance than the 316L stainless steel but its capacity for repassivation is lower. A damaging factor of influence on the pitting corrosion behaviour is the presence of non-metallic inclusions on the surface which reduce the pitting corrosion resistance by almost a half. © 1999 Elsevier Science Ltd. All rights reserved.

[ES] Desde que la MA 956 fue propuesta como posible nuevo biomaterial en base a su buena resistencia a la corrosión frente a sueros fisiológicos, un largo camino, aún sin finalizar, se ha recorrido, en el que se ha llevado a cabo una caracterización exhaustiva de esta aleación a temperatura ambiente con fines tecnológicos bien definidos: su posible uso en aplicaciones biomédicas, bien sea como prótesis de cadera o de rodilla y para implantes dentales. Los estudios se han llevado a cabo comparando esta aleación con los materiales más comúnmente utilizados en implantes ortopédicos como aleaciones de titanio y polietileno., [EN] Since the MA 956 was proposed as a possible new biomaterial due to its good corrosión resistance valúes in physiological fluids a long way, still not finished, has been done. An exhaustive characterization of this alloy at room temperature has been developed. The technological objetives are well established: the possible use of this material for biomedical applications as hip or knee prostheses and as dental implants. The study was performed comparing the results of this alloy with the materials used nowadays as surgical implants, i.e., titanium alloys and polyethylene.

The surface composition of MA 956 superalloy both as-received and after four exposure times at 1100 °C has been investigated by energy dispersive x-ray spectrometry (EDX) and x-ray photoelectron spectroscopy (XPS). The passive layer of the as-received sample is mainly formed by Cr- and Fe-oxides. Heat treatment leads to the formation of an alumina layer on which small nodules grow. XPS spectra evidence the presence of titanium and yttrium oxides at the surface of the heat-treated samples, suggesting Y and Ti outward diffusion through the alumina layer. Iron and chromium oxides at the topmost surface layers are observed only for short heat-treatment times.

We report on a synchrotron radiation photoemission study of an Fe3Al-type alloy. The influence of different annealing treatments on the surface electronic structure has been investigated. The Al-2p photoemission spectra show slight differences among samples with a very small metallic Al component. From the Fe-3p and the valence band photoemission spectra, a higher surface Fe-content for the sample having a defective ordered B2 structure is observed. This finding is explained in terms of the bulk structure and the thickness of the passive layer. After determination of the surface composition of the samples, electrochemical experiments in Hank's solution have been performed in order to determine the influence of the passive layer composition on the corrosion behaviour of the samples. The low corrosion rates observed for all specimens indicate that the passive layer formed in air on the material surface gives high corrosion protection to the alloy for all heat treatments. © 1997 Elsevier Science Ltd. All rights reserved.

Two Ni-P coatings of different thickness on a mild steel are submitted to laser surface melting at different scanning rates. The corrosion behaviour of the coatings in sodium sulphate 0.1 M solution is studied by several electrochemical techniques. The corrosion behaviour is usually determined by the presence of cracks in the coatings. It is shown that the initial corrosion rates of the electroless Ni-P coatings submitted to laser treatment are lower than those in electroless Ni-P coatings without laser treatment. The corrosion rates increase after several days, except for the sample with the maximum coating thickness laser treated at the maximum scanning rate. For the Ni-P coatings of minimum thickness, a high dilution with the steel substrate takes place when the coatings are melted by laser. As a consequence, the Fe content of the Ni-P coating increases, particularly in the dendritic phase which undergoes selective attack. This dilution effect is greatest for the samples laser treated at the minimum scanning rate in which corrosion takes place uniformly in the whole coating.