Biomaterial Studies on AISI 316L Stainless Steel after Magnetoelectropolishing

Tadeusz Hryniewicz,Krzysztof Rokosz,Massimiliano Filippi

doi:10.3390/ma2010129

Tadeusz Hryniewicz, Krzysztof Rokosz + Show 1 more

Open Access

https://doi.org/10.3390/ma2010129

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Abstract

The polarisation characteristics of the electropolishing process in a magnetic field (MEP – magnetoelectropolishing), in comparison with those obtained under standard/conventional process (EP) conditions, have been obtained. The occurrence of an EP plateau has been observed in view of the optimization of MEP process. Up-to-date stainless steel surface studies always indicated some amount of free-metal atoms apart from the detected oxides and hydroxides. Such a morphology of the surface film usually affects the thermodynamic stability and corrosion resistance of surface oxide layer and is one of the most important features of stainless steels. With this new MEP process we can improve metal surface properties by making the stainless steel more resistant to halides encountered in a variety of environments. Furthermore, in this paper the stainless steel surface film study results have been presented. The results of the corrosion research carried out by the authors on the behaviour of the most commonly used material − medical grade AISI 316L stainless steel both in Ringer’s body fluid and in aqueous 3% NaCl solution have been investigated and presented earlier elsewhere, though some of these results, concerning the EIS Nyquist plots and polarization curves are also revealed herein. In this paper an attempt to explain this peculiar performance of 316L stainless steel has been undertaken. The SEM studies, Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were performed on 316L samples after three treatments: MP – abrasive polishing (800 grit size), EP – conventional electrolytic polishing, and MEP – magnetoelectropolishing. It has been found that the proposed magnetoelectropolishing (MEP) process considerably modifies the morphology and the composition of the surface film, thus leading to improved corrosion resistance of the studied 316L SS.

Highlights

Several positive features concerning electropolished metal surface have been ascribed to the so called plateau of the polarisation curve
Type UNS S31603 316L stainless steel is a low-carbon version of the AISI 316 stainless steel used extensively for many purposes due to its superior corrosion resistance, smoothness, biocompatibility and cleanability after electropolishing treatment [17,18,19,20]
We began our studies with a conventional electropolishing EP to compare the results with the ones obtained under EP using a magnetic field

Summary

Introduction

Several positive features concerning electropolished metal surface have been ascribed to the so called plateau of the polarisation curve. The use of an externally applied magnetic field to the electropolishing process (EP) provides the treated metal surface with some new properties and better characteristics, including microroughness, hydrophilicity, contact angle, corrosion resistance, and oxide film morphology [1,2,3,4,5,6]. The addition of an external magnetic field to the process of electropolishing significantly minimizes microtopography by lowering microroughness and minimizing the actual surface area on the micro- and nano scales [1,2,3,5,7,8,9,10]. The remarkable improvement in corrosion resistance of electropolished surfaces of austenitic stainless steels is caused by several interconnected events occurring during the electropolishing process, discussed extensively elsewhere [3,9,10,11,12,13,14,15,20,21]

Results

Discussion

Conclusion