HRYNIEWICZ Tadeusz Koszalin University of Technology

Spoluautoři ROKOSZ Krzysztof

Electrochemical polishing of metals and alloys is one of the most often used finishing operations, specifically in case of metallic biomaterials with complicated shapes (coronary stents, prostheses, etc.), from which in addition to the desired surface roughness and/or shine, a high corrosion resistance and the lack of carcinogenic elements in the surface layer, are also desired. Some additional effects may be obtained when the magnetic field is used in the process called the magnetoelectropolishing MEP. Our studies indicate that the MEP process additionally affects the chemical composition of the surface layer as well as corrosion resistance and mechanical properties. The research work has been concerned on the studies and development of electrochemical polishing in the magnetic field (MEP) in comparison with the standard electropolishing methods performed without stirring (EP) and the process with the forced electrolyte mixing (MIX). There were both ferromagnetic (unalloyed and chromium ferritic, martensitic) steels, paramagnetic steels (austenitic stainless steel) as well as other materials such as cobalt and NiTi alloys, and CP titanium, taken into consideration in the studies. The advanced techniques were used in the studies, such as, scanning electron miscoscopy (SEM/EDS), X-ray Photoelectron Spectroscopy (XPS), Secondary Ion Mass Spectroscopy (SIMS), and nanoindentation measurements. For the corrosion studies, the following electrochemical methods were used: open circuit potential OCP, potentiodynamic curves PC, and electrochemical impedance spectroscopy EIS measurements. The MEP process is advised mainly due to the opportunity to enrich the surface layer with the chromium (austenitic steels) or titanium (Nitinol) compounds. The surface layers of biomaterials after MEP process contain much lower amount of carcinogenic compounds like chromium VI oxidation stage (Cr6+) (austenitic stainless steel) and nickel compounds (austenitic stainless steel & Nitinol) versus those ones obtained after EP & MIX treatments. It is interesting that apart from the significant modification of the surface layer obtained after MEP, also mechanical properties, such as nanohardness, modulus of elasticity, and mechanical resistance to bending and torsion, undergo considerable changes. All these changes make the MEP process very promising for application in many clean industries, such as medical equipment and devices, electronics, food industry, etc.