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Additive manufacturing technologies have several well-known advantages; however, the surface quality of the printed parts is poor, compromising the corrosion and mechanical properties. Thus, surface finishing treatments are necessary. The most post-processing treatments proposed in the literature are mechanical or chemical. The formers are contact techniques and cannot be suitable for complex geometry, while the latter use strong and dangerous reagents. This paper is aimed to investigate the effect of the electropolishing treatment, a contactless technique, using an eco-friendly electrolytic solution in reducing the roughness and improving the fatigue properties of Ti6Al4V specimens produced by electron beam melting technology. Several parameters affecting the effectiveness of the electropolishing treatment have been investigated, as interelectrode distance, stirring rate and duration time. An optimal combination of them allowed a uniform surface treatment and a significant roughness reduction (64% of Sa reduction for cylindrical specimens). Under sinusoidal loading conditions with a maximum stress of 378 MPa and a stress ratio equal to R = 0.1, the mean fatigue life of electropolished dog-bone specimens was 250% longer than that of as-built specimens.

The additive manufacturing process is gaining increasing interest due to the possibility of producing components with a complex shape, very close to the final geometry. On the other hand, however, it involves a very high final roughness, such as to compromise the mechanical performance and resistance to corrosion. Therefore, post-processing treatments are required. Electropolishing could be the ideal treatment to reduce the roughness of these components. It is known that various parameters, such as the type of electrolyte solution, the voltage or current applied, the treatment time, agitation, etc. They could affect the effectiveness of the electropolishing treatment. The most used electrolyte solutions are dangerous to handle and difficult and expensive to dispose of. The aim of this work was to study a possible electropolishing treatment on Ti6Al4V samples made by Electron Beam Melting (EBM) using an “eco-friendly” electrolytic solution.

To reduce the environmental impact of surface chemical conversion processes, companies producing aluminum alloy laminates need to convert plants that use "rinse" technology, (i.e., processes that require rinsing after treatment surface in the conversion bath) to "no-rinse" (i.e., processes that do not need to be rinsed) with the aim of reducing the amount of water used in their processing cycles. At the same time, there is a need to eliminate hexavalent chromium (CrVI) from any type of industrial process, due to its known carcinogenic effects. In this study, therefore, the protective properties offered by specimens obtained from AA3005 alloy laminates, subjected to "no-rinse" CrIII-based phospho- chromate processes, both naked and painted, were studied, comparing them with those exhibited by specimens processed using the traditional CrVI-based "rinse" process. The experimental results have shown that the specimens treated with the no-rinse procedure involve a greater resistance to corrosion than those rinse treated. Therefore, the no-rinse CrIII-based treatments seem to be a valid alternative to the rinse ones, due to the increase in corrosion resistance of the material, the evident reduction of the environmental impact, as well as the reduction of the costs of process.

The increasing the corrosion resistance of aluminum alloys using chromium-free surface treatments, especially for materials in contact with food, has become a urgent need. In order to reduce the environmental impact and save the available natural resources, surface treatments so called "no-rinse" are being developed. This paper presents the results obtained using some commercial surface conversion treatments, evaluating the corrosion resistance exhibited by bare and coated specimens. The results have shown that use of product containing Ti and Zr salts determines an increase in the corrosion resistance of the protective system if compared to a classical chromate based system. In addition, the former also reduces water consumption as the process is of the no-rinse type.

The natural oxide layer, which spontaneously covers the surface of aluminium and its alloys, is well adherent to the surface, but it does not show adequate corrosion resistance in many conditions. In order to improve the material anti-corrosion performance, it is necessary to replace the surface oxide by a conversion coating. The first step to do this is to prepare the alloy surface to subsequent treatments. The pre-treatment implemented before the conversion treatment is one of the main factors responsible for the performance of the conversion coating. It involves several phases, including desmutting that encompasses the part immersion in an acid or alkaline solution bath. In this work, the influence of hydrofluoric acid concentration in the desmutting bath’s formulation was investigated. The samples surface were characterised by using electrochemical techniques, glow discharge optical emission spectrometry and contact angle measurements.

MATERIALS AND METHODS. It is well known that the parameter "average roughness" Ra is often used to characterize the roughness of dental implants, especially in the commercial field, but it does not define the surface state; there are, however, various other roughness parameters defining the device topography in a univocal way. The physical meaning of some roughness parameters, like Sa, Sq, Sku and Ssk has thus been considered. The effect of sandblasting duration (1, 2, 4 and 8 min) and hydrofluoric acid etching, as well as their combined or synergic effect on the surface topography of commercially pure titanium (Ti CP) grade 2 and grade 4, have been investigated in order to highlight the use of those parameters. The experimental results statistical significance has been validated using analysis of variance.RESULTS AND CONCLUSIONS. We propose to use the roughness parameters Sa, Sq, Sku and Ssk to evaluate dental implant topography. Their implementation shows that: (i) it is possible to distinguish between surfaces that have undergone different treatments; (ii) the experimental results obtained show that sandblasting, performed on Ti CP grade 2 and Ti CP grade 4, under the same experimental conditions, induces completely different topographic features. To compare results obtained by different authors, the above parameters should be used in describing the implants surface state.OBJECTIVES. The aim of this study is to enhance the current understanding of the physical meaning of some roughness parameters, and to promote their implementation as routine methodology for assessing the state of surfaces.

The increasing use of titanium in the biomedical field arises from the excellent biocompatibility due to the ability to spontaneously become covered with a passive layer. Several studies have shown that some surface treatments can enhance the biological response and corrosion resistance of the implants. The aim of this work is to study the effect of surface treatments of sandblasting and etching with HF on the electrochemical behavior in biological environment and on the roughness of two types of commercially pure titanium, Ti grade 2 and Ti grade 4, used for prostheses and dental implants. The electrochemical characterization has allowed showing that the passive current density increases with the duration of the sandblasting treatment for both alloys. A smaller increase was found in samples subjected to blasting and subsequent etching. It follows that the variation of specific surface induced by blasting is partially canceled by the chemical treatment. The value of passive current density was used to assess the extent of the increase of the real surface of the samples. The roughness analysis showed that the blasting process produces a surface with a large number of peaks, and that the etching with HF tends to level the surface attenuating peaks. The sandblasting and etching treatments, alone or combined, significantly modify the surface of the samples and the magnitude of this change differs depending on the alloy used. Finally, it is proposed to use four roughness parameters to characterize the treated surfaces.

Fatigue corrosion phenomenon is a form of degradation that is because of the combined occurrence of a mechanical cyclical stress and a corrosive environment. Fatigue corrosion can be an issue in commercial and military aircraft, and has the potential to affect the structural integrity and the useful life of an aerostructure. Although the distinct consequences of both fatigue and corrosion have been extensively documented for aluminum alloys, their synergistic action is not completely understood and continues to be an area of considerable scientific and industrial interest. In this paper, a novel approach is proposed and applied for monitoring the electrochemical behavior of different types of aluminum alloy samples while they are subjected to fatigue loading. Cyclic load experiments were conducted on bare 2024T3 and 6056T4 aluminum alloy samples in the presence of an aggressive aerated solution of 3.5% NaCl over a range of frequencies. The R-ratio was 0. Two different aluminum alloys have been tested in both high- and low-cycle fatigue. In the former case, the maximum stress experienced by the specimen is lower than the material yield strength, which means that the average expected number of cycles to failure is high; in the latter case, the maximum stress experienced by the specimen during the test is higher than the material yield strength, which means that the average expected number of cycles to failure is low. The open circuit potential(OCP) wasmonitored versus time during the tests described above. The observed OCP variations are interpreted as the occurrence of corrosion during crack initiation and propagation at the air formed oxide/solution interface film. As expected, there is a more pronounced influence of corrosion at lower fatigue frequencies. Crack propagation allows bulk material to be progressively more exposed to the aggressive environment, which stimulates accelerated crack propagation, resulting in a lower fatigue resistance. Copyrightc 2010 John Wiley & Sons, Ltd.