Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Investigation of corrosion properties of metals for degradable implant applications
KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF. (Surface physics)ORCID iD: 0000-0001-6332-0501
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [sv]

Nedbrytbara metaller utgör en ny klass av biomaterial med potential attersätta permanenta material i tillfälliga applikationer. Detta för att minskarisken för långvariga biverkningar. I den pågående forskningen för att utvecklanya nedbrytbara metaller är screening av nya material genom in vitro testmetoderett attraktivt alternativ för att undvika onödiga, tidskrävande ochdyrbara djurstudier.Denna avhandling fokuserar på in vitro-testning av zink- och magnesiumbaserademetaller. Inverkan av faktorer såsom sammansättningen av testlösningen,buffersystemet, belastning samt mikrostruktur hos legeringar undersöktes.Genom att använda elektrokemiska in situ tekniker såsom impedansspektroskopi(EIS) är det möjligt att studera gränssnittet mellan metall ochlösning och karakterisera egenskaperna hos den korroderande ytan. Ex situytkaraktäriseringstekniker som svepelektronmikroskopi och infraröd spektroskopianvändes sedan för att komplettera resultaten av de elektrokemiskamätningarna.Korrosionen av zink i Ringer’s lösning fanns vara närmare in vivo korrosionän korrosionen i fosfatbuffrad saltlösning (PBS). Ringers lösning är därför denföredragna testmiljön för långsiktig utvärdering av zinkbaserade metallerDet biologiska buffersystemet (CO2/H2CO3) bör företrädesvis användasför att stabilisera pH-värdet på testlösningen vid magnesiumnedbrytning. NärHEPES användes för att stabilisera pH ökade korrosionshastigheten på grundav bildning av mindre skyddande skikt av korrosionsproduktMöjligheten att använda helblod och plasma som mer kliniskt relevantatestmiljöer utvärderades och befanns producera reproducerbara resultat.Bildning av ett korrosionsskikt bestående av både organiskt och oorganisktmaterial detekterades på zink i både plasma och helblod.När zink prover i helbod utsattes för belastning förhindrade korrosionsskiktetbildningen av mikrosprickor och förtidigt brott av provet. Det varvidare möjligt att detektera tidig sprickbildning på grund av belastning avMagnesium AZ61-legering med EIS.Adsorption av organiska species på zinkytan under anodisk polariseringökar yttäckningen av Zn-joner i helblod. Den ökade yttäckningen leder sedantill utfällningen av ett skyddande skikt av zinkfosfater och en minskadkorrosionshastighet vid högre potentialer.Korrosion av Zn-Mg och Zn-Ag legeringar i Ringers lösning befanns skevia selektiv upplösning. Lokal utfällning av korrosionsprodukter och bildningav ett poröst, mindre skyddande skikt av korrosionsprodukter hittades påZn-Mg legeringar. Den selektiva upplösningen av Zn-Ag legering orsakade enanrikning av AgZn3 vilket kan påverka biokompatibiliteten av ett implantatmed tiden.

Abstract [en]

Degradable metallic implants are a new class of biomaterials with potentialto replace permanent materials in temporary applications to reduce therisk of long term adverse effects.This thesis focuses on in vitro testing of zinc and magnesium based metals.As new degradable metals are developed screening of new materials within vitro test methods is an attractive option to avoid unnecessary, time consumingand expensive animal studies. The influence of factors such as ioniccomposition of the test solution, buffer system, strain and alloy compositionwas investigated. By employing electrochemical in situ techniques such asimpedance spectroscopy it is possible to study the metal-solution interfaceand determine the properties of the corroding surface. Ex situ surface characterizationtechniques such as scanning electron microscopy and infraredspectroscopy were then used to complement the results of the electrochemicalmeasurements.The importance of appropriate selection of the test solution is highlightedin this work. Zinc was found to corrode in Ringer’s solution by a mechanismcloser to in vivo corrosion than in a phosphate buffered saline solution(PBS).Ringer’s solution is therefore the more appropriate test environment for longterm evaluation of zinc based metals.When evaluating the corrosion of Zn-Mg and Zn-Ag alloys in Ringer’ssolution selective dissolution was found to occur for both types of alloys. Localprecipitation and formation of a porous, less protective, layer of corrosionproducts was found for Zn-Mg alloys. The selective dissolution of Zn-Agalloy caused an enrichment of AgZn3 on the surface which may affect thebiocompatibility of the alloy.The use of HEPES to maintain the pH of the test solution increasedthe corrosion rate of magnesium due to formation of a less protective layerof corrosion products. Magnesium corrosion should therefore preferably bestudied in solutions where the pH is maintained by the biological buffer systemCO2/H2CO3.In addition to saline solutions human whole blood and plasma were evaluatedas more clinically relevant in vitro environments. They were found toproduce reproducible results and to be suitable for short term experiments.Formation of a corrosion product layer comprised of both organic and inorganicmaterial was detected on zinc in both plasma and whole blood.During anodic polarization the adsorption of organic species on the zincsurface was found to increase the surface coverage of Zn ions in whole blood.The increased surface coverage then allowed for precipitation of a protectivelayer of Zn5(PO4)3 and a subsequent decrease in corrosion rate at higherpotentials.When subjecting zinc samples to strain the organic/inorganic corrosionproduct formed in whole blood was observed by impedance spectroscopy toprevent micro cracking and premature failure.The cracking of magnesium alloy samples under applied strain was alsocharacterized by impedance. Changes in surface properties due to crack initiation

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. , p. 80
Series
TRITA-FYS, ISSN 0280-316X ; 2017:58
Keyword [en]
biodegradable, metal, zinc, magnesium, corrosion, electrochemistry
National Category
Bio Materials Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-215970ISBN: 978-91-7729-528-0 (electronic)OAI: oai:DiVA.org:kth-215970DiVA, id: diva2:1150454
Public defence
2017-11-10, sal C (Sven-Olof Öhrvik), Electrum, kistagången 16, kista, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note

QC 20171019

Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2017-11-02Bibliographically approved
List of papers
1. Degradation of zinc in saline solutions, plasma, and whole blood
Open this publication in new window or tab >>Degradation of zinc in saline solutions, plasma, and whole blood
2016 (English)In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 104, no 6, p. 1141-1151Article in journal (Refereed) Published
Abstract [en]

The initial degradation of zinc has been investigated through exposures to simulated and real body fluids of increasing complexity: phosphate buffered saline (PBS), Ringer's saline solution, human plasma, and whole blood. Real body fluids were used to close the electrolyte gap between simulated and in vivo environment. Polarization of zinc in whole blood show a passive response not present in other electrolytes. The analysis shows a decrease in corrosion rate with time for plasma and whole blood and an increase for PBS and Ringer's. During exposure to plasma and whole blood a bi-layered corrosion product with poor adherence was formed over a uniformly corroding surface. The corrosion products comprise a mixture of inorganic material and biomolecules. Samples degrading in PBS were prone to localized corrosion and formed thick porous corrosion products of primarily zinc phosphates while in Ringer's solution a gel like layer of zinc carbonate was formed over an interface with shallow pits. The use of whole blood or plasma as electrolytes for short term in vitro evaluation of potential biodegradable metals may provide an improved understanding of the behavior in vivo, while Ringer's solution is preferred over PBS for long term degradation studies of zinc.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keyword
zinc, biodegradable, corrosion, blood, electrochemistry
National Category
Biomedical Laboratory Science/Technology
Identifiers
urn:nbn:se:kth:diva-190549 (URN)10.1002/jbm.b.33458 (DOI)000380032300010 ()26061136 (PubMedID)2-s2.0-84978640711 (Scopus ID)
Note

QC 20160817

Available from: 2016-08-17 Created: 2016-08-12 Last updated: 2017-11-28Bibliographically approved
2. The influence of buffer system and biological fluids on the degradation of magnesium
Open this publication in new window or tab >>The influence of buffer system and biological fluids on the degradation of magnesium
2017 (English)In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 105, no 6, p. 1490-1502Article in journal (Refereed) Published
Abstract [en]

The influence of frequently used buffer system 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) compared to CO2/HCO3- on the corrosion of magnesium is investigated. Samples were immersed in simulated body fluid (m-SBF) while monitored by electrochemical impedance spectroscopy (EIS) for up to 30 days. In CO2/HCO3- the initial corrosion rate was 0.11 mm yr-1. An inner protective layer of magnesium oxide was formed within the first 30 min exposure and subsequently covered by an outer layer of apatite within 24 h. The corrosion mechanism thereafter is best described as passive pitting with a porosity of ∼10%. Using HEPES as buffer agent increased the corrosion rate to 3.37 mm yr-1. Cross sectional microscopy show a porous outer corrosion layer allowing rapid diffusion of aggressive ions through the film. Here the EIS results are best described by an active pitting model with an inner layer 5 to 10 times less protective compared to the inner layer formed without HEPES. Further the suitability of human whole blood and plasma as in vitro models for Mg degradation was evaluated. Mg corrosion caused coagulation after 24 h in both biological fluids. The corrosion during the first 24 h is similar to the corrosion in m-SBF with HEPES.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keyword
Bioresorbable, Corrosion, Degradation, Surface characterization, Body fluids, Carbon dioxide, Diffusion in liquids, Electrochemical corrosion, Electrochemical impedance spectroscopy, Magnesium, Phosphate minerals, Pitting, Biological fluids, Corrosion layers, Corrosion mechanisms, In-vitro models, Protective layers, Simulated body fluids, Corrosion rate
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:kth:diva-186773 (URN)10.1002/jbm.b.33685 (DOI)000407055400019 ()27098550 (PubMedID)2-s2.0-84964329339 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20160627

Available from: 2016-06-27 Created: 2016-05-13 Last updated: 2017-10-19Bibliographically approved
3. Influence of strain on the corrosion of magnesium alloys and zinc in physiological environments
Open this publication in new window or tab >>Influence of strain on the corrosion of magnesium alloys and zinc in physiological environments
2017 (English)In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 48, p. 541-550Article in journal (Refereed) Published
Abstract [en]

During implantation load-bearing devices experience stress that may influence its mechanical and corrosion profile and potentially lead to premature rupture. The susceptibility to stress corrosion cracking (SCC) of the Mg-Al alloy AZ61 and Zn was studied in simulated body fluid (m-SBF) and whole blood by slow strain rate (SSR) testing in combination with electrochemical impedance spectroscopy (EIS) and further ex situ analysis including scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. AZ61 was found to be highly susceptible to SCC. EIS analysis show that although the majority of cracking occurred during the apparent plastic straining, cracking initiation occurs already in the elastic region at similar to 50% of the ultimate tensile strength (UTS). Shifts in EIS phase angle and open circuit potential can be used to detect the onset of SCC. Zinc demonstrated a highly ductile behavior with limited susceptibility to SCC. No significant decrease in UTS was observed in m-SBF but a decrease in time to failure by similar to 25% compared to reference samples indicates some effect on the mechanical properties during the ductile straining. The formation of micro cracks, similar to 10 mu m deep, was indicated by the EIS analysis and later confirmed by ex situ SEM. The results of SSR analysis of zinc in whole blood showed a reduced effect compared to m-SBF and no cracks were detected. It appears that formation of an organic surface layer protects the corroding surface from cracking. These results highlight the importance of considering the effect of biological species on the degradation of implants in the clinical situation. Statement of Significance Strain may deteriorate the corrosion properties of metallic implants drastically. We study the influence of load on the corrosion properties of a magnesium alloy and zinc by a combination of electrochemical impedance spectroscopy (EIS) and slow strain rate analysis. This combination of techniques has previously not been used for studying degradation in physiological relevant electrolytes. EIS provide valuable information on the initial formation of cracks, detecting crack nucleation before feasible in slow strain rate analysis. This sensitivity of EIS shows the potential for electrochemical methods to be used for in situ monitoring crack formation of implants in more applied studies.

Place, publisher, year, edition, pages
Elsevier, 2017
Keyword
Stress corrosion cracking (SCC), Slow strain rate (SSR), Zinc, Magnesium alloy, AZ61, Electrochemical impedance spectroscopy (EIS), Biodegradable
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-203169 (URN)10.1016/j.actbio.2016.10.030 (DOI)000393247000046 ()27780765 (PubMedID)2-s2.0-85005916279 (Scopus ID)
Note

QC 20170315

Available from: 2017-03-15 Created: 2017-03-15 Last updated: 2017-11-29Bibliographically approved
4. Characterization of the Protective Layer Formed on Zinc in Whole Blood
Open this publication in new window or tab >>Characterization of the Protective Layer Formed on Zinc in Whole Blood
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The advantageous degradation properties of zinc in a biological environment are related to the presence of a protective corrosion layer composed of both organic and inorganic components. However, the mechanisms governing its formation and how the organic species influence its properties have not been established. Here we study the protective layer formation during anodic polarization in whole blood by in situ electrochemical impedance spectroscopy (EIS) as well as infrared spectroscopy and scanning electron microscopy. Simulated body fluid (m-SBF) was used as a reference media to discern the influence of the organic species present in whole blood. Protective zinc phosphate layers form on the Zn surface in both solutions, but of different nature and through diverse mechanisms. In m-SBF the passivating thin film formation occur already at open circuit potential, reducing the corrosion current compared to exposure in whole blood by a factor of 103. The high corrosion current in whole blood can be explained by a process including rapid protein adsorption preventing the initial formation of a protective phosphate layer. EIS analysis detected an inductive arc in whole blood at low overpotentials, before the onset of protective film formation, indicating the presence of adsorbed Zn2ions. The coverage of Zn ions approach 100% of the active surface at 110 mV. At this critical surface coverage a reaction between the adsorbed Zn ions and PO42- takes place which results in formation of a protective, porous, film of ~1 μm thickness. The inorganic component of the protective film formed in whole blood was characterized as Zn(PO4)2(OH)2·3H2O.

National Category
Biomaterials Science
Identifiers
urn:nbn:se:kth:diva-215664 (URN)
Funder
Swedish Research Council
Note

QC 20171017

Available from: 2017-10-12 Created: 2017-10-12 Last updated: 2017-10-19Bibliographically approved
5. Zn-Mg and Zn-Ag degradation mechanism under biologically relevant conditions
Open this publication in new window or tab >>Zn-Mg and Zn-Ag degradation mechanism under biologically relevant conditions
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Zinc alloys form a promising new class of biodegradable metals that combine suitable mechanical properties with the favorable degradation properties of pure zinc. However, the current understanding of the influence of alloying elements on the corrosion of zinc alloys, in biologically relevant media, is limited. We studied the degradation of three alloys, Zn 4 wt% Ag, Zn 0.5 wt% Mg and Zn 3 wt% Mg by in situ electrochemical impedance spectroscopy (EIS). After exposure for 1h or 30 days the samples were characterized by infrared spectroscopy and scanning electron microscopy (SEM). The presence of secondary phases in the alloy microstructure induced selective corrosion and increased degradation rate. An increase in surface inhomogeneity was evident by EIS analysis both at short (hours) as well as long immersion times (days). The microgalvanic corrosion of the Zn-Ag alloy resulted in enrichment of the AgZn3 phase at the sample surface. The enrichment of Ag and potential release of AgZn3 particles may result in complications during the tissue regeneration. The Zn-Mg alloy surface was depleted of the Mg-rich phase after 8-12 days. The selective dissolution caused local precipitation of2corrosion products and a thicker corrosion layer with larger pore size consistent with increased corrosion rate.

National Category
Biomaterials Science
Identifiers
urn:nbn:se:kth:diva-215665 (URN)
Funder
Swedish Research Council
Note

QC 20171017

Available from: 2017-10-12 Created: 2017-10-12 Last updated: 2017-10-19Bibliographically approved

Open Access in DiVA

Kappa(8850 kB)79 downloads
File information
File name FULLTEXT02.pdfFile size 8850 kBChecksum SHA-512
b772499a9a4e600fdbf8f68a269cf4f9d2410ae94a9fc31a57b5009ca2c3cdaa29b7553333d063033360865457615a06e18c81202a9a1ff6a18cc96312b8f8b5
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Beaussant Törne, Karin
By organisation
Material Physics, MF
Bio MaterialsMetallurgy and Metallic Materials

Search outside of DiVA

GoogleGoogle Scholar
Total: 93 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 179 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
v. 2.34-SNAPSHOT
|