Polarization characteristics of magnetoelectropolishing stainless steels

The aim of the study is to present the polarization characteristics of electropolishing process carried out in a magnetic field (MEP—magnetoelectropolishing), in comparison with the ones obtained under standard/conventional process of electropolishing (EP) conditions. The polarization characteristics have been considered as the most important factor in establishing effective treatment conditions. With this paper we would like to show the results of the studies concerning the effects of a magnetic field strength and electropolishing conditions (convection, temperature) on the electrochemical polarization characteristics. Specifically the occurrence of electropolishing EP plateau has been observed in view of optimization of magnetoelectropolishing MEP process. It has been found that, depending on the magnetic field strength, under higher potentials the current density has been growing with the increase of potential to a certain value only. Afterwards the current density remains unchanged. This behavior in the course of polarization curves obtained under high potentials has been revealed to be the effect of cyclically disclosure of sample surface and re-submerge, this resulting in the “second limiting current”.     

Electrochemical and XPS studies of AISI 316L stainless steel after electropolishing in a magnetic field

The thermodynamic stability and corrosion resistance of surface oxide layer are the most important features of stainless steels. Electrochemical polishing (EP) is the most extensively used surface technology for austenitic stainless steels. We have modified this surface technology by introducing a magnetic field to the system. With this new process called the magnetoelectropolishing (MEP) we can improve metal surface properties by making the stainless steel more resistant to halides encountered in a variety of environments.In this paper, the corrosion research results are presented on the behaviour of the most commonly used material - medical grade AISI 316L stainless steel. The corrosion investigations have been concerned on the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and polarisation curves studies in the Ringer’s body fluid under room temperature (25 °C). The X-ray photoelectron spectroscopy (XPS) was performed on 316L samples after three treatments: MP - abrasive polishing (800 grit size), EP - conventional electrolytic polishing, and MEP - magnetoelectropolishing. The comparison of the corrosion behaviour of the stainless steel’s surface after these processes was also carried out. The purpose of XPS studies was to reveal the surface film composition and the reason of this modified corrosion behaviour. It has been found that the proposed MEP process modifies considerably the composition of the surface film and improves the corrosion resistance of the same 316L SS studied.     

Surface characterization of AISI 316L biomaterials obtained by electropolishing in a magnetic field

The paper deals with comparison of the results obtained by electropolishing AISI 316L surfaces in an externally applied magnetic field with those of a standard electropolishing process. All electrochemical investigation methods, electrochemical impedance spectroscopy (EIS), polarization curve measurements, and surface analytical methods such as surface roughness measurements and scanning electron microscopy were carried out to determine the efficacy of electropolishing in a magnetic field.     

Investigation of selected surface properties of AISI 316L SS after magnetoelectropolishing

The aim of the paper is to present the surface film composition formed on AISI 316L SS and its surface microhardeness after electropolishing (EP) and magnetoelectropolishing (MEP) in a wide range of the process conditions. The electropolishing EP process has been performed under natural convection (in still electrolyte), and under a forced convection (moderate stirring below 0.1 m/s), both on the polarization plateaux and much above it. Another series of experiments was carried out on AISI 316L SS samples prepared by MEP at 350 mT. The samples prepared by mechanical abrasive polishing, with the grit size up to 1000, served as a reference. First of all, concerning the surface film composition, a big difference in iron contents was observed between the samples after mechanical polishing and electropolishing. On the other hand, there were much less differentiations of chromium contents in surface film formed on 316L SS samples after each of the studied electropolishing conditions, and even mechanical polishing. The total Cr:Fe ratio was also studied, with quite promising results obtained. At the end the conclusions concerning the selection of proper electropolishing conditions have been formulated.