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Metal release from stainless steel powders and massive sheets - comparison and implication for risk assessment of alloys
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.ORCID iD: 0000-0003-2145-3650
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.ORCID iD: 0000-0003-2206-0082
2013 (English)In: Environmental Sciences: Processes and Impacts, ISSN 2050-7887, Vol. 15, no 2, 381-392 p.Article in journal (Refereed) Published
Abstract [en]

Industries that place metal and alloy products on the market are required to demonstrate them being safe for all intended uses, and that any risks to humans, animals or the environment are adequately controlled. This requires reliable and robust in-vitro test procedures. The aim of this study is to compare the release of alloy constituents from stainless steel powders of different grades (focus on AISI 316L) and production routes into synthetic body fluids with the release of the same metals from massive sheet in relation to material and surface characteristics. The comparison is justified by the fact that the difference between massive surfaces and powders from a metal release/dissolution and surface perspective is not clearly elucidated within current legislations. Powders and abraded and aged (24 h) massive sheets were exposed to synthetic solutions of relevance for biological settings and human exposure routes, for periods up to one week. Concentrations of released iron, chromium, nickel, and manganese in solution were measured, and the effect of solution pH, acidity, complexation capacity, and proteins elucidated in relation to surface oxide composition and its properties. Implications for risk assessments based on in-vitro metal release data from alloys are elucidated.

Place, publisher, year, edition, pages
2013. Vol. 15, no 2, 381-392 p.
Keyword [en]
Patch Test Reactivity, Particles In-Vitro, Ion Release, Nickel Release, Pure Metals, Orthodontic Appliances, Ferrochromium Alloy, Contact-Dermatitis, Oxygen Reduction, Aisi 316l
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:kth:diva-105520DOI: 10.1039/C2EM30818EISI: 000315397700008Scopus ID: 2-s2.0-84874439615OAI: oai:DiVA.org:kth-105520DiVA: diva2:571305
Note

QC 20130213

Available from: 2012-11-22 Created: 2012-11-22 Last updated: 2016-08-30Bibliographically approved
In thesis
1. Stainless Steel in Biological Environments – Relation between Material Characteristics, Surface Chemistry and Toxicity
Open this publication in new window or tab >>Stainless Steel in Biological Environments – Relation between Material Characteristics, Surface Chemistry and Toxicity
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Triggered by the regulatory need of the industry to demonstrate safe use of their alloy products from an environmental and health perspective, and by the significant lack of metal release data and its correlation to material and surface characteristics for iron- and chromium-based alloys, a highly interdisciplinary in-depth research effort was undertaken to assess the relation between material/surface characteristics and toxicity with main emphasis on stainless steel alloys. This thesis focuses predominantly on studies made on AISI 316L both as massive sheet and as powder particles, but includes also results for other stainless steel grades and reference metals and metal oxides.

 

The work comprises multi-analytical bulk and surface characterizations combined with particle characterizations and corrosion investigations, all correlated with in-depth kinetic metal release (bioaccessibility) studies as a function of route of manufacture, powder particle characteristics, surface finish, stainless steel grade, solution composition, pH, acidity and complexation capacity, as well as the presence of proteins. Speciation (chemical form) measurements were in addition conducted of released chromium, and of metal species in the surface oxide. Protein interactions were investigated in terms of adsorption, protein-metal complexation both at the surface and in solution, and the relative strength of protein-stainless steel surface interaction was addressed. In vitro and in vivo toxicological studies were conducted for the same inert-gas-atomized 316L powder sized < 4µm.

 

Bulk and surface oxide properties, such as phase, structure, morphology, chemical and electrochemical stability, protein-surface interactions, bioavailability of released metals, were all clearly evident to largely influence the metal release process and any induced toxicity. The route of manufacture was shown to strongly influence the bulk and surface oxide characteristics of stainless steel powders, hence also their electrochemical and catalytic properties, as well as the release/dissolution of metals from the powders (Papers VIII, XIII, XIV-XVII). The release of metals from both stainless steel sheets and powders was in general low compared to pure iron or nickel metal, and highly dependent on bulk and surface characteristics, the composition, complexation capacity and buffering capacity (and pH) of the solution, as well as on many experimental factors including time and sonication (Papers VI, VIII, XI, and XVII).

 

Surface-protein interactions strongly enhanced the release of alloy constituents (Papers IX, XI, and XVII). Iron was preferentially released (manganese in the case of inert-gas-atomized stainless steel powders) (Papers VIII, XI, and XVII). Protein-stainless steel surface interactions were most probably governed by chemisorption at given experimental conditions (Papers XI-XII). A strong protein-adsorption was evident for all stainless steel surfaces investigated, independent of protein charge, size or structure (Paper IX). Protein-metal complexes were formed both at the surface and in solution (Papers X-XII). Differences in protein charge and type resulted in varying degrees of interaction with differences in the extent of enhanced metal release as a consequence (Papers XI-XII). The inert-gas-atomized stainless steel powder sized <4 µm induced neither any significant increase of lysis of erythrocytes (rupture of red blood cells) nor any cytotoxicity, but resulted in a slight DNA damage in in vitro toxicity measurements (Paper VI). No adverse effects were however observed in an in vivo 28-day repeated-dose inhalation study on rats using the same powder (Paper VII).

 

The most important bulk, surface, particle, and experimental factors governing the bioaccessibility properties of stainless steel were identified and mechanistically elucidated. Detailed knowledge of all factors is essential for accurate hazard or risk assessment of metal alloys and enables read-across possibilities with materials of the same or similar characteristics. However, in cases where data is different from known systems for one factor or more, bioaccessibility data should be generated before any risk assessment is made.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. XIV, 38 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:57
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-105521 (URN)978-91-7501-521-7 (ISBN)
Public defence
2012-12-14, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20121126

Available from: 2012-11-26 Created: 2012-11-22 Last updated: 2012-11-26Bibliographically approved
2. Metal Release and Corrosion of Stainless Steel in Simulated Food Contact
Open this publication in new window or tab >>Metal Release and Corrosion of Stainless Steel in Simulated Food Contact
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Knowledge on metal release behaviour of stainless steels used in food processing applications and cooking utensils is essential within the framework of human health risk assessments. Recently, a new European test guideline (the CoE protocol) has been implemented to ensure safety of metals and alloys in food contact, such as stainless steels. This guideline suggests 5 gL-1 citric acid (pH 2.4) as a food simulant for acidic foods of pH ≤ 4.5. So far, limited assessments exist that investigate the correlation between the bioaccessibility, material characteristics, corrosion behaviour and surface chemistry of stainless steel for food application tests using citric acid. Therefore, this doctoral thesis comprises an in–depth interdisciplinary and multi–analytical research effort to fill this knowledge gap.

This work includes thorough investigations of a range of stainless steel grades in simulated food contact as a function of different important parameters such as grades, surface finish, temperature, pH, solution composition, metal complexation and buffering capacity, concentration of the complex forming agents, loading, and repeated usage. This is accomplished by kinetic studies of metal release, electrochemical, and surface analytical investigations. Another focus of this thesis is to assess the dominating metal release process in citric acid or chloride containing solutions of varying pH.

This study suggests protonation (at acidic pH) and surface complexation (at weakly acidic and neutral pH) as the predominant metal release mechanisms for stainless steel in citric acid solutions. Solution complexation may also play a role by hindering metal precipitation at weakly acidic and neutral pH, and metal release from surface defects / inclusions may initially be important for non-passivated surfaces.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. 63 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:32
National Category
Materials Chemistry Metallurgy and Metallic Materials
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-191474 (URN)978-91-7729-067-4 (ISBN)
External cooperation:
Public defence
2016-09-22, F3, Lindstedtsvägen 26, KTH Campus, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160831

Available from: 2016-08-31 Created: 2016-08-30 Last updated: 2016-08-31Bibliographically approved

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Hedberg, YolandaOdnevall Wallinder, Inger

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