Surface–rain interactions: Differences in copper runoff for copper sheet of different inclination, orientation, and atmospheric exposure conditions

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Surface modified Ti6Al4V for enhanced bone bonding ability - effects of silver and corrosivity at simulated physiological conditions from a corrosion and metal release perspective

Abstract Different surface treatments, with and without silver (Ag), of a Ti6Al4V alloy for increased bone bonding ability were investigated and compared with non-treated surfaces. Studies were conducted at 37 °C in phosphate buffered saline (PBS, pH 7.4) of varying hydrogen peroxide (H2O2) and bovine serum albumin (BSA) concentrations. Increased levels of metal release and corrosion were observed in the presence of both H2O2 and BSA due complexation with Ti and Al in the surface oxide, respectively. Ag release was enhanced by the presence of BSA. Galvanic effects by Ag were minor, but possibly observed in the most corrosive environment

Corrosion and runoff rates of Cu and three Cu-alloys in marine environments with increasing chloride deposition rate

AbstractBare copper sheet and three commercial Cu-based alloys, Cu15Zn, Cu4Sn and Cu5Al5Zn, have been exposed to four test sites in Brest, France, with strongly varying chloride deposition rates. The corrosion rates of all four materials decrease continuously with distance from the coast, i.e. with decreasing chloride load, and in the following order: Cu4Sn>Cu sheet>Cu15Zn>Cu5Al5Zn. The patina on all materials was composed of two main layers, Cu2O as the inner layer and Cu2(OH)3Cl as the outer layer, and with a discontinuous presence of CuCl in between. Additional minor patina constituents are SnO2 (Cu4Sn), Zn5(OH)6(CO3)2 (Cu15Zn and Cu5Al5Zn) and Zn6Al2(OH)16CO3·4H2O/Zn2Al(OH)6Cl·2H2O/Zn5Cl2(OH)8·H2O and Al2O3 (Cu5Al5Zn). The observed Zn- and Zn/Al-containing corrosion products might be important factors for the lower sensitivity of Cu15Zn and Cu5Al5Zn against chloride-induced atmospheric corrosion compared with Cu sheet and Cu4Sn.Decreasing corrosion rates with exposure time were observed for all materials and chloride loads and attributed to an improved adherence with time of the outer patina to the underlying inner oxide. Flaking of the outer patina layer was mainly observed on Cu4Sn and Cu sheet and associated with the gradual transformation of CuCl to Cu2(OH)3Cl of larger volume. After three years only Cu5Al5Zn remains lustrous because of a patina compared with the other materials that appeared brownish–reddish.Significantly lower release rates of metals compared with corresponding corrosion rates were observed for all materials. Very similar release rates of copper from all four materials were observed during the fifth year of marine exposure due to an outer surface patina that with time revealed similar constituents and solubility properties

Inter-laboratory Validation of Bioaccessibility Testing for Metals

Bioelution assays are fast, simple alternatives to in vivo testing. In this study, the intra- and inter-laboratory variability in bioaccessibility data generated by bioelution tests were evaluated in synthetic fluids relevant to oral, inhalation, and dermal exposure. Using one defined protocol, five laboratories measured metal release from cobalt oxide, cobalt powder, copper concentrate, Inconel alloy, leaded brass alloy, and nickel sulfate hexahydrate. Standard deviations of repeatability (s[subscript r]) and reproducibility (s[subscript R]) were used to evaluate the intra- and inter-laboratory variability, respectively. Examination of the s[subscript R]:s[subscript r] ratios demonstrated that, while gastric and lysosomal fluids had reasonably good reproducibility, other fluids did not show as good concordance between laboratories. Relative standard deviation (RSD) analysis showed more favorable reproducibility outcomes for some data sets; overall results varied more between- than within-laboratories. RSD analysis of s[subscript r] showed good within-laboratory variability for all conditions except some metals in interstitial fluid. In general, these findings indicate that absolute bioaccessibility results in some biological fluids may vary between different laboratories. However, for most applications, measures of relative bioaccessibility are needed, diminishing the requirement for high inter-laboratory reproducibility in absolute metal releases. The inter-laboratory exercise suggests that the degrees of freedom within the protocol need to be addressed.Keywords: Metals, Inter-laboratory validation, Read-across, Bioelution, Alloys, Classification, Bioaccessibility, UVCBsKeywords: Metals, Inter-laboratory validation, Read-across, Bioelution, Alloys, Classification, Bioaccessibility, UVCB

Metal release from stainless steels and the pure metals in different media

This study has been triggered by the fact that stainless steel is being increasingly used in new applications, where possible environmental effects may be a matter of concern. When stainless steel is exposed to a given environment, a key issue is the release of small amounts of the main alloying elements iron, chromium, nickel and molybdenum. Published release rate data of these elements turned out to be sparse. Furthermore, only little was known about the role of different parameters that may affect the release rate, such as degree of alloying, exposure time and surface finish. Hence, the aim of this study was to develop methodological means and to provide accurate metal release rates of alloying constituents from different grades of stainless steels- austenitic, ferritic and duplex- when exposed to selected environments: artificial rain and synthetic body fluids. The results and discussion have been summarised in this thesis by formulating and answering ten questions, all believed to be crucial for the understanding of possible environmental effects of stainless steels. Some common conclusions could be drawn, independent of stainless steel grade and exposure condition. Iron was always preferentially released, and the release rates of chromium, nickel and molybdenum (when measured) were significantly lower than of iron, also when considering the bulk proportion of these elements. The release rate of all elements was initially high and decreased with exposure time, mainly because of an observed enrichment of chromium in the passive film formed. The release rates of iron (2 μgcm-2week-1) and nickel (0.08 μgcm-2week-1) from stainless steel from grades 304 and 316 exposed to artificial rain were much lower than corresponding rates for the pure metals (750 μgcm-2week-1 released Fe and 15 μgcm-2week-1 released Ni), whereas chromium exhibited similar release rates from stainless steel and the pure metal (0.1 μgcm-2week-1). This implies that the common procedure to calculate release rates, based on the pure metals and the nominal steel composition, significantly overestimates release rates of iron and nickel from stainless steel, but not of chromium. Total release rates from seven stainless steel grades in synthetic body fluid were found to decrease with increasing alloy content in the following release rate order: grade 409 >> grade 430 > grades 316L ≈ 201 ≈ 2205 ≈ 304 > grade 310. The release rate was highly sensitive to pH of the synthetic body fluid but only slightly sensitive to stainless steel surface finish.QC 2012021

Bioaccessibility of Stainless Steels : Importance of Bulk and Surface Features

With increasing environmental awareness, the desire to protect human beings and the environment from adverse effects induced by dispersed metals has become an issue of great concern and interest. New policies, such as REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) within the European Community, have been implemented to reduce hazards posed by the use of chemicals on producers and downstream users. The generation of exposure assessment data and relevant test procedures able to simulate realistic scenarios are essential in such legislative actions. This doctoral study was initiated to fill knowledge gaps related to the metal release process of stainless steels. A wide range of stainless steel grades, fourteen in total, were investigated. They cover a very broad range of applications, and the focus in the thesis was to simulate a few selected exposure scenarios: precipitation, the human body and food intake. Comparisons were made between metal release from stainless steel alloys and the pure metals that constitute each stainless steel in order to explore the differences between alloys and pure metals, and to provide quantitative data on metal release rates of different alloy constituents. Because of similar surface properties between stainless steel and pure chromium, this metal exhibits similar release rates, whereas iron and nickel exhibit significantly lower release rates as alloy components than as pure metals. Detailed studies were also performed to elucidate possible relations between metal release and steel surface properties. Key parameters turned out to be chromium enrichment of the self-passivating surface film, surface roughness, the electrochemically active surface area and the microstructure of the steel substrate. The degree of metal release increased with decreasing chromium content in the surface oxide, increasing surface roughness, and increasing presence of inhomogeneities in the bulk matrix. More detailed studies were initiated to possibly correlate the nucleation of metastable pits and the extent of metal release. Evidence was given that metastable pits exist even when the stainless steel is passive, and may cause extremely short-lived bursts of released metal before the surface film repassivates again.QC 2010081

Bioaccessibility of Stainless Steels : Importance of Bulk and Surface Features

With increasing environmental awareness, the desire to protect human beings and the environment from adverse effects induced by dispersed metals has become an issue of great concern and interest. New policies, such as REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) within the European Community, have been implemented to reduce hazards posed by the use of chemicals on producers and downstream users. The generation of exposure assessment data and relevant test procedures able to simulate realistic scenarios are essential in such legislative actions. This doctoral study was initiated to fill knowledge gaps related to the metal release process of stainless steels. A wide range of stainless steel grades, fourteen in total, were investigated. They cover a very broad range of applications, and the focus in the thesis was to simulate a few selected exposure scenarios: precipitation, the human body and food intake. Comparisons were made between metal release from stainless steel alloys and the pure metals that constitute each stainless steel in order to explore the differences between alloys and pure metals, and to provide quantitative data on metal release rates of different alloy constituents. Because of similar surface properties between stainless steel and pure chromium, this metal exhibits similar release rates, whereas iron and nickel exhibit significantly lower release rates as alloy components than as pure metals. Detailed studies were also performed to elucidate possible relations between metal release and steel surface properties. Key parameters turned out to be chromium enrichment of the self-passivating surface film, surface roughness, the electrochemically active surface area and the microstructure of the steel substrate. The degree of metal release increased with decreasing chromium content in the surface oxide, increasing surface roughness, and increasing presence of inhomogeneities in the bulk matrix. More detailed studies were initiated to possibly correlate the nucleation of metastable pits and the extent of metal release. Evidence was given that metastable pits exist even when the stainless steel is passive, and may cause extremely short-lived bursts of released metal before the surface film repassivates again.QC 2010081

Metal release from stainless steels and the pure metals in different media

This study has been triggered by the fact that stainless steel is being increasingly used in new applications, where possible environmental effects may be a matter of concern. When stainless steel is exposed to a given environment, a key issue is the release of small amounts of the main alloying elements iron, chromium, nickel and molybdenum. Published release rate data of these elements turned out to be sparse. Furthermore, only little was known about the role of different parameters that may affect the release rate, such as degree of alloying, exposure time and surface finish. Hence, the aim of this study was to develop methodological means and to provide accurate metal release rates of alloying constituents from different grades of stainless steels- austenitic, ferritic and duplex- when exposed to selected environments: artificial rain and synthetic body fluids. The results and discussion have been summarised in this thesis by formulating and answering ten questions, all believed to be crucial for the understanding of possible environmental effects of stainless steels. Some common conclusions could be drawn, independent of stainless steel grade and exposure condition. Iron was always preferentially released, and the release rates of chromium, nickel and molybdenum (when measured) were significantly lower than of iron, also when considering the bulk proportion of these elements. The release rate of all elements was initially high and decreased with exposure time, mainly because of an observed enrichment of chromium in the passive film formed. The release rates of iron (2 μgcm-2week-1) and nickel (0.08 μgcm-2week-1) from stainless steel from grades 304 and 316 exposed to artificial rain were much lower than corresponding rates for the pure metals (750 μgcm-2week-1 released Fe and 15 μgcm-2week-1 released Ni), whereas chromium exhibited similar release rates from stainless steel and the pure metal (0.1 μgcm-2week-1). This implies that the common procedure to calculate release rates, based on the pure metals and the nominal steel composition, significantly overestimates release rates of iron and nickel from stainless steel, but not of chromium. Total release rates from seven stainless steel grades in synthetic body fluid were found to decrease with increasing alloy content in the following release rate order: grade 409 >> grade 430 > grades 316L ≈ 201 ≈ 2205 ≈ 304 > grade 310. The release rate was highly sensitive to pH of the synthetic body fluid but only slightly sensitive to stainless steel surface finish.QC 2012021

Chemical Stability of Chromium Carbide and Chromium Nitride Powders Compared with Chromium Metal in Synthetic Biological Solutions

Chromium carbide (Cr-C) and chromium nitride (Cr-N) powders were compared with a chromium metal powder (Cr-metal) to evaluate their chemical stability in solution. All three powders were exposed in five different synthetic biological solutions of varying pH and chemical composition simulating selected human exposure conditions. Characterisation of the powders, using GI-XRD, revealed that the predominant bulk crystalline phases were Cr7C3 and Cr2N for Cr-C and Cr-N respectively. The outermost surface of Cr-C, determined by XPS, contained Cr7C3 and Cr2O3 and the corresponding measurement on Cr-N revealed Cr2N and CrN apart from Cr2O3. The presence of Cr2O3 was verified by XPS investigations of the Cr-metal powder. The mean particle size was similar for Cr-metal and Cr-N but slightly smaller for Cr-C. All three powders were poorly soluble and released very low amounts of chromium (&lt;0.00015 μg Cr/μg loaded particles) independent on test solution. Slightly higher chromium concentrations were determined in the more acidic media (pH 1.7 and 4.5) compared with the near-neutral solutions (pH 7.2 and 7.4). Cr-C released the lowest amount of Cr despite having the largest surface area a feature attributed to the strong covalent bonds within the matrix.QC 20160303</p

Applying Generic Water Quality Criteria to Cu and Zn in a Dynamic Aquatic Environment&mdash;The Case of the Brackish Water Formation Str&ouml;mmen-Saltsj&ouml;n

The EU Water Framework Directive stipulates that all EU waterways shall have good chemical and ecological status by 2027. Methodologies are described for how to assess and classify waterbodies and make 7-year management plans. Aquatic risk assessment methodologies and environmental quality standards are defined and a biotic ligand model methodology is available to assess the influence of water chemistry on the ability of aquatic organisms to take up metals. Aquatic status classification practices of naturally occurring river basin-specific metals are discussed, specifically how Cu and Zn water quality criteria guideline values have been adopted and defined for Swedish coastal and estuarine waters and how well they represent possible ecological risks. Calculations of bioavailability and ecotoxicity are conducted using recognised models for the Str&ouml;mmen-Saltsj&ouml;n water body in Stockholm, in which naturally occurring metals, especially Cu, have among the highest background concentrations of Sweden. Proposals are made to improve risk assessment methodologies to better reflect the vitality of living organisms, and to what extent current levels of these metals in Swedish waterways may influence their welfare. The study concludes that a more local assessment including, e.g., studies of the benthic fauna would be relevant for ecological status classification