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Esophageal nitinol stents are an established method for treating swallowing difficulties caused by obstructing cancer. This raesearch investigates the influence of different qualities of raw metal alloys in combination with production technology on corrosion resistance in standardized simulated gastric fluid (SGF). Four different international stent manufacturers produced samples of their standard stents from nitinol sourced from three different alloy manufacturers. The stents were subjected to a 6-week immersion in SGF. During the immersion, the surface was studied at specified intervals using microscopy. The surface of the samples was also studied by X-ray Photoelectron Spectroscopy and after immersion the released ions were analyzed. Results demonstrated that both raw material and certain steps in the manufacturing process negatively affect corrosion resistance. Analysis of the SGF showed that the amount of nickel released is proportional to the degree of corrosion attack. Finally, current accepted standard test methods are inadequate for assessing susceptibility to corrosion by gastric acid and should take the low pH of the implanted environment into account. Conversely, certain measures in the manufacturing process are able to reduce the impact of the base material on corrosion susceptibility. [ABSTRACT FROM AUTHOR]

Titanium beta alloys represent the new generation of materials for the manufacturing of joint implants. Their Young's modulus is lower and thus closer to the bone tissue compared to commonly used alloys. The surface tribological properties of these materials should be improved by ion implantation. The influence of this surface treatment on corrosion behaviour is unknown. The surface of Ti-36Nb-6Ta, Ti-36Nb-4Zr, and Ti-39Nb titanium β-alloys was modified using nitrogen ion implantation. X-ray photoelectron spectroscopy was used for surface analysis, which showed the presence of titanium, niobium, and tantalum nitrides in the treated samples and the elimination of less stable oxides. Electrochemical methods, electrochemical impedance spectra, polarisation resistance, and Mott–Schottky plot were measured in a physiological saline solution. The results of the measurements showed that ion implantation does not have a significant negative effect on the corrosion behaviour of the material. The best results of the alloys investigated were achieved by the Ti-36Nb-6Ta alloy. The combination of niobium and tantalum nitrides had a positive effect on the corrosion resistance of this alloy. After surface treatment, the polarization resistance of this alloy increased, 2.3 × 106 Ω·cm2, demonstrating higher corrosion resistance of the alloy. These results were also supported by the results of electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

This paper evaluates the amount of KMnO4 in simulated concrete pore solution (pH 12.8) on the corrosion behaviour of hot-dip galvanized steel (HDG). In the range of used MnO4− (10−4, 10−3, 10−2 mol·L−1), corrosion behaviour is examined with regard to hydrogen evolution and composition (protective barrier properties) of forming corrosion products. The corrosion behaviour of HDG samples is evaluated using Rp/Ecorr and EIS. The composition of corrosion products is evaluated using SEM, XRD, XPS and AAS. The effective MnO4− ion concentration to prevent the corrosion of coating with hydrogen evolution is 10−3 mol·L−1; lower concentrations only prolong the time to passivation (corrosion with hydrogen evolution). The highest used MnO4− concentration ensures corrosion behaviour without hydrogen evolution but also leads to the formation of less-protective amorphous corrosion products rich in MnII/MnIII phases. [ABSTRACT FROM AUTHOR]

Recently, there has been an extension of three‐dimensional (3D) printing technology of metal materials in the medical field. Additive technology has made it possible to manufacture customized implants. However, 3D printing products often require surface treatment. The possible treatments include acid etching. This study investigated the effect of surface etching on the corrosion resistance of Ti–6Al–4V alloy concerning biological applications. The samples were etched in a mixture of hydrofluoric acid and nitric acid. The corrosion behaviour was described by measuring the time dependence of polarization resistance in a saline solution and surface analysis. The results showed that etching creates a fluoride‐rich layer on the surface, which negatively affects the corrosion behaviour of the material for up to 24 hr. Cytocompatibility tests showed that the resulting layer does not affect the biocompatibility of the material. [ABSTRACT FROM AUTHOR]

Abstract Corrosion behaviour of Ti-35Nb-7Zr-5Ta β titanium alloy nitrided by ion implantation was examined. Nitrogen ions were implanted with different fluences in the range from 1·1017 to 9·1017 cm−2 and an accelerating voltage of 90 kV. The specific effects of the nitrogen fluence on structural changes of the implantation zone showed the relationship between nitrogen concentration, nitride formation and corrosion behaviour. Nitrogen depth profiles measured by glow discharge optical emission spectroscopy showed the saturation limit approx. 60 at.% leading to the exo -diffusion of nitrogen. X-ray photoelectron spectroscopy indicated increasing formation of surface nitrides with the fluence of implanted nitrogen, up to the saturation fluence of 4 · 1017 cm−2. Oversaturation induced a decrease in nitrogen concentration, accompanied by a reduction in the amount of surface nitrides, and accompanied by blistering. The corrosion tests in physiological saline solution show high resistance of the implanted surfaces to corrosion attack. The corrosion resistance increased with increasing fluence up to saturation fluence. Fluences higher than saturation one caused decrease of the corrosion resistance to the level of lower fluences. All nitrogen implanted surfaces showed higher resistance than non-implanted surface. The surface nitriding has no influence on the susceptibility to the localized corrosion attack. The formation of surface nitrides and their concentration, rather than the defects of an oversaturated surface, affect the corrosion behaviour. Highlights • The Ti-35Nb-7Zr-5Ta β-Ti alloy was nitrided by low-temperature ion implantation. • Nitrogen saturation was observed at fluence of 4 ⋅ 1017 cm−2 leading to the blistering. • Oversaturation caused reduction in concentration of nitrogen and titanium nitrides. • Corrosion behaviour was improved with increasing fluence of nitrogen up to saturation. [ABSTRACT FROM AUTHOR]

Esophageal nitinol stents are an established method for treating swallowing difficulties caused by obstructing cancer. As a consequence of improved patient survival, stent failure and an increasing need for re-intervention is a rapidly emerging problem. This research investigates the influence of different quality of raw metal alloys in combination with production technology on corrosion resistance. Four different international stent manufacturers produced samples of their standard stents from nitinol sourced from three different alloy manufacturers. The corrosion resistance was evaluated by cyclic potentiodynamic scans according to the ASTM standards in phosphate buffered saline solution. Because of targeted application of the stent in gastrointestinal tract, the simulated gastric fluid was also used for corrosion measurement. In addition, the surface of the samples was studied by X-ray Photoelectron Spectroscopy and Mott-Schottky analysis. Results demonstrated that both, raw material and certain steps in the manufacturing process affects corrosion resistance. Conversely, other certain measures in the manufacturing process are able to reduce the impact of the base material on corrosion susceptibility. Furthermore, we could demonstrate that a key factor influencing corrosion resistance is the concentration of nickel on the surface. Current accepted standard test methods with phosphate buffered saline solution are inadequate for assessing susceptibility to corrosion by gastric acid and should take the low pH of the implanted environment into account. Understanding the corrosive process and the impact of surface finishes is key to developing stents suitable for long-term palliation. • Corrosion behavior of NiTi in simulated gastic fluid was studied. • Corrosion mechanism was stated. • Influence of material and manufacturing process on corrosion was described. • Current testing methods for GIT NiTi stents are inadequate. [ABSTRACT FROM AUTHOR]

Springs made of low-alloy carbon steels are often exposed to the effects of a corrosive environment, such as high humidity and concentration of road salt, rain and snow erosion, temperature fluctuations in combination with dynamic loading and mechanical wear. One of the possibilities to improve their resistance in a corrosive environment is their microalloying by Cr, Ni, Mo or Cu. This study tested the effect of microalloying of 54SiCr6 steel by copper on the corrosion behavior in model rainwater and saltwater. The corrosion resistance of the steel samples was tested using electrochemical tests by measuring the polarization resistance and the anodic parts of the potentiodynamic curves at three different temperatures. The surface of the steel samples was observed using SEM/EDS, surface analysis, and XRD diffraction. The measurement results showed that copper in the amount of approx. 1.5 wt % does not affect the microstructure of the spring steel 54SiCr6 after the heat treatment significantly, but improves the corrosion resistance during short-term exposure in both model rainwater and saltwater. • Cu does not affect the structure of spring steel negatively. • Cu improves the corrosion resistance in model rainwater and saltwater. • Dual layer of corrosion products is formed in model saltwater. [ABSTRACT FROM AUTHOR]

To increase an orthopedic implant's lifetime, researchers are now concerned on the development of new titanium alloys with suitable mechanical properties (low elastic modulus–high fatigue strength), corrosion resistance and good workability. Corrosion resistance of the newly developed titanium alloys should be comparable with that of pure titanium. The effect of medical preparations containing fluoride ions represents a specific problem related to the use of titanium based materials in dentistry. The aim of this study was to determine the corrosion behavior of β titanium alloy Ti–39Nb in physiological saline solution and in physiological solution containing fluoride ions. Corrosion behavior was studied using standard electrochemical techniques and X-ray photoelectron spectroscopy. It was found that corrosion properties of the studied alloy were comparable with the properties of titanium grade 2. The passive layer was based on the oxides of titanium and niobium in several oxidation states. Alloying with niobium, which was the important part of the alloy passive layer, resulted in no significant changes of corrosion behavior. In the presence of fluoride ions, the corrosion resistance was higher than the resistance of titanium. [ABSTRACT FROM AUTHOR]

DLC-type layers offer a good potential for application in medicine, due to their excellent tribological properties, chemical resistance, and bio-inert character. the presented study has verified the possibility of alloying DLC layers with titanium, with coatings containing three levels of titanium concentration prepared. titanium was present on the surface mainly in the form of oxides. Its increasing concentration led to increased presence of titanium carbide as well. the behavior of the studied systems was stable during exposure in a physiological saline solution. electrochemical impedance spectra practically did not change with time. Alloying, however, changed the electrochemical behavior of coated systems in a significant way: from inert surface mediating only exchange reactions of the environment in the case of unalloyed DLC layers to a response corresponding rather to a passive surface in the case of alloyed specimens. the effect of DLC layers alloying with titanium was tested by the interaction with a simulated body fluid, during which precipitation of a compound containing calcium and phosphorus - basic components of the bone apatite - occurred on all doped specimens, in contrast to pure DLC. t he results of the specimens' surface colonization with cells test proved the positive effect of titanium in the case of specimens with a medium and highest content of this element. [ABSTRACT FROM AUTHOR]

Purpose -- This work aims to focus on evaluation of the ability of cathodically deposited ZrO[sub 2]-based coatings to stabilise the surface of silver against tarnishing caused by S[sup 2-]-based species and comparison of these coatings with Cr oxide-based coating. Design/methodology/approach -- The coatings were evaluated using inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), impedance spectroscopy (EIS) and galvanostatic reduction of specimens exposed to H[sub 2]S vapours. Findings -- The kinetics of deposition were studied and optimum conditions for coating formation were determined. The options of manual application suitable for practical use were studied also. Zr specimens showed better barrier properties than did a chromated specimen. The best properties were observed on a specimen with a manually fast-applied coating. However, Zr coating does not provide as good protection from tarnishing as chromate. The structure of the Cr coating contains species of chromate that oxidize species of S[sup 2-]. Originality/value -- The paper provides new information regarding the anticorrosive properties of cathodically deposited ZrO[sub 2] coating as an alternative to Cr coating for the preservation of silver surfaces. [ABSTRACT FROM AUTHOR]

Porous materials allow for easier osseointegration of implants and their firmer connection with the bone. The presence of pores in a material may become a source of both mechanical and corrosion problems. The presented study explored a Ti-39Nb alloy with a porosity of 0-33%. Specimens were exposed in the physiological solution of two pH values. In view of this material's possible use in dental applications, the effect of fluoride ions on its corrosion behaviour was studied. The open circuit potential and polarization resistance were measured. Data concerning susceptibility to crevice corrosion were obtained from potentiostatic measurements based on the ASTM F746 standard.In terms of corrosion behaviour, specimens with a lower porosity were not much different from the non-porous material. Porosity produced its effect at the level of 24 and 33%. It is obvious that porosity affects corrosion behaviour of this type of material. This conclusion was confirmed by measurements of susceptibility to crevice corrosion which grew with the specimens' increasing porosity. Corrosion resistance of the Ti-39Nb alloy was comparable with that of the compact material, but the presence of pores initiated a local attack of the material. [ABSTRACT FROM AUTHOR]

• Surface properties of Ti-35Nb-7Zr-5Ta alloy with various pre-treatments have been investigated. • Morphological changes in macroscale and in microscale have been observed. • The corrosion resistance was significantly reduced after ion sputter etching. • MG-63 cells adhered well on surfaces that had been pre-treated in various ways. Pre-treatment methods for titanium alloys are of great importance, both as regards the treatment of the surfaces of the implant and as regards the pre-deposition phase of the coating processes and the surface modifications. We have investigated the impact of chemical, electrochemical and ion sputter etching on the surface properties, the corrosion stability and the MG-63 cell response of Ti-35Nb-7Zr-5Ta alloy. In the initial state, the samples have a mechanically polished surface. The pre-treatments that were applied led to significant morphological changes in microscale and also in nanoscale. The wettability of the pre-treated surfaces varied from hydrophilicity to hydrophobicity. Changes in contact angle were controlled by surface chemistry rather than changes in morphology and roughness. Native oxides and suboxides of alloying elements with a predominant amount of Nb 2 O 5 were found to provide high corrosion stability of Ti-35Nb-7Zr-5Ta alloy after mechanical polishing, after chemical etching and after electrochemical etching. Significantly reduced corrosion resistance in a physiological saline solution was observed for the ion sputtered surface. A decreasing trend in the cell spreading area correlated with increasing surface roughness and decreasing polarization resistance. There is discussion of the causes of the changes in surface properties and cell behaviour. [ABSTRACT FROM AUTHOR]