Il Prof. Tadeusz Hryniewicz dell’Universita’ di Koszalin, Polonia, terra’ lunedi’ 8 ottobre 2012 alle ore 15.00 presso l’Aula Savagnone del DIEETCAM un Seminario dal titolo: “Magnetoelectropolishing of Metallic Biomaterials: A revolution in surface finishing”.
Electropolishing (EP) is an electrochemical anodic process with controlled dissolution of metal surface, performed under the conditions of pseudopassivity. Magnetoelectropolishing (MEP) is the process enhanced by involving a magnetic field to modify the surface properties. Alteration in the metallic surface properties, in view of increasing biocompatibility and/or haemocompatibility of biomaterials, is the main purpose of the MEP process. Thus the MEP is controlled by voltage U (V), or current I(A), (or current density i(A/dm2) and the magnetic field intensity B(mT). One more variable included to MEP process (B) provides a better opportunity to obtain the metal surface of required properties.
Though the MEP may be applied to any metal or alloy, the most significant and valuable effects are usualy obtained on biomaterials; they are the increased corrosion resistance, modified surface energy (increased wettability on request) and highly improved mechanical properties (nanohardness, Young’s modulus, resistance to fracture under bending, etc.). In fact, a very compact and tight film formed on the surface after MEP affects multiple chemical, physical, and mechanical properties. Stainless steels (AISI 316LVM), CP Titanium Grade 2, and Ti alloys (binary, ternary and quaternary alloys), as well as other biomaterials (Co-Cr, Nb) are of a special attention.
Our study methods include: surface roughness (Ra) and interferometry (Sa) measurements; Scanning Electron Spectroscopy SEM/EDX studies; Contact Angle Measurement CAM; Auger AES and X-ray Photoelectron Spectroscopy XPS (the highly increased Cr/Fe ratio, and/or Ti/Ni ratio); Secondary Ion Mass Spectroscopy SIMS and GDMS (a considerable dehydrogenation observed); corrosion studies (OCP, CP, EIS) with extremely high Pitting Resistance Equivalent Number PREN obtained; nanoindentation testing (significant changes observed); study of resistance to fracture (static and dynamic testing). One example of the recently obtained corrosion results to compare: Nitinol after MEP with Eb equaling 1130 mV (literature data), and AISI 316L SS after MEP with Eb reaching 1100 up to 1400 mV (our own studies).
*E-mail: Tadeusz.Hryniewicz@tu.koszalin.pl
