title: Influence of trace impurities on the in vitro and in vivo degradation of biodegradable Mg-5Zn-0.3Ca alloys.
abstract: The hydrogen evolution method and animal experiments were deployed to investigate the effect of trace impurity elements on the degradation behavior of high-strength Mg alloys of type ZX50 (Mg-5Zn-0.3Ca). It is shown that trace impurity elements increase the degradation rate, predominantly in the initial period of the tests, and also increase the material's susceptibility to localized corrosion attack. These effects are explained on the basis of the corrosion potential of the intermetallic phases present in the alloys. The Zn-rich phases present in ZX50 are nobler than the Mg matrix, and thus act as cathodic sites. The impurity elements Fe and Mn in the alloy of conventional purity are incorporated in these Zn-rich intermetallic phases and therefore increase their cathodic efficiency. A design rule for circumventing the formation of noble intermetallic particles and thus avoiding galvanically accelerated dissolution of the Mg matrix is proposed.
authors.affiliation: Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Hofstetter
authors.affiliation: Department of Orthopaedics and Orthopaedic Surgery, Medical University Graz, 8036 Graz, Austria.
authors.forename: E
authors.initials: E
authors.lastname: Martinelli
authors.affiliation: Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Pogatscher
authors.affiliation: Laboratory for Joining Technologies and Corrosion, EMPA, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Schmutz
authors.affiliation: Christian Doppler Laboratory for Early Stages of Precipitation, Vienna University of Technology, 1040 Vienna, Austria.
authors.forename: E
authors.initials: E
authors.lastname: Povoden-Karadeniz
authors.affiliation: Department of Orthopaedics and Orthopaedic Surgery, Medical University Graz, 8036 Graz, Austria.
authors.forename: A M
authors.initials: AM
authors.lastname: Weinberg
authors.affiliation: Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: P J
authors.initials: PJ
authors.lastname: Uggowitzer
authors.affiliation: Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland. Electronic address: joerg.loeffler@mat.ethz.ch.
authors.forename: J F
authors.initials: JF
authors.lastname: Löffler
mesh_terms: D020341:Absorbable Implants; D000497:Alloys / Q000737:chemistry*; D000818:Animals; D001826:Body Fluids / Q000737:chemistry; D001858:Bone Nails; D002118:Calcium / Q000737:chemistry*; D003343:Corrosion; D004553:Electric Conductivity; D004866:Equipment Contamination; D008274:Magnesium / Q000737:chemistry*; D008297:Male; D008422:Materials Testing; D051381:Rats; D017207:Rats, Sprague-Dawley; D015032:Zinc / Q000737:chemistry*
chemical_list: D000497:Alloys; D008274:Magnesium; D015032:Zinc; D002118:Calcium
keywords: Biodegradation; Corrosion; Intermetallic phases; Magnesium; Mg–Zn–Ca alloys