Corrosion Properties of Electropolished AISI 316L Austenitic Biomaterial in Relation to Electropolishing Conditions

Abstract

Electropolishing is recommended for various biomedical applications of austenitic biomaterials because it enables to achieve high brightness, very low surface roughness, excellent corrosion resistance and reduced bacterial attachment without residual surface tensions. The quality of an electropolished surface depends strongly on the composition of used electrolyte and on the applied electropolishing conditions. In this article the corrosion properties of eight AISI 316L surfaces electropolished in the same solution but at the different conditions were evaluated on the bases of the electrochemical impedance spectroscopy (EIS) test and exposure immersion test. The aim was to find whether in the frame of recommended electropolishing conditions (temperature, current density, time) the optimal combination exists which would provide the best corrosion properties of the surface passive film. The results showed that the electropolishing temperature 50 ºC should be preferred due to the lower roughness parameters and minimizing the possibility of the bacterial attachment.

Plasma Electrolytic Polishing—An Ecological Way for Increased Corrosion Resistance in Austenitic Stainless Steels

“…It points to the high corrosion resistance and biomedical safety with the minimum metal release into the human body environment [16,46,47] that correlates with the results of the performed independent electrochemical corrosion tests. Unlike these results, in the exposure test performed under the same conditions on the EP surface of 316L stainless steel, the authors [28] observed more pronounced pitting corrosion damage and higher corrosion rates (dependent on EP conditions 0.013-0.024 g/(m 2 .day)). The received surface (Figure 8a) showed the lower quality of the passive film, which enabled the local penetration of the chloride anions in numerous places and the initiation The received surface (Figure 8a) showed the lower quality of the passive film, which enabled the local penetration of the chloride anions in numerous places and the initiation of pitting corrosion.…”

“…It points to the high corrosion resistance and biomedical safety with the minimum metal release into the human body environment [16,46,47] that correlates with the results of the performed independent electrochemical corrosion tests. Unlike these results, in the exposure test performed under the same conditions on the EP surface of 316L stainless steel, the authors [28] observed more pronounced pitting corrosion damage and higher corrosion rates (dependent on EP conditions 0.013-0.024 g/(m 2 •day)).…”

“…If compared to the surface roughness after EP, the authors [25,27] reported approximately the same R a values of the EP austenitic steel surfaces. The authors [28] presented the same R∆q values for the 316L surfaces after EP was performed at 40 • C.…”

“…This means that an expensive and environment-unfriendly EP process brought a markedly lower surface quality in comparison to the PEP process. The authors [28] studied the corrosion properties of 316L stainless steel surfaces electropolished in the same solution (orthophosphoric acid + sulphuric acid + water) but at the different conditions (temperature, current density, time). The R ct value closest to PEP and PPEP surfaces was 559.3 kΩ•cm 2 obtained for specimen EP treated at 40 • C for 10 min at 0.8 A/cm 2 .…”

Surface Quality and Corrosion Resistance of 316l Stainless Steel Electropolished Using Phosphoric – Sulfuric Acids

“…While 14 minutes electropolishing time was found to give the maximum gloss, this study also proved that increasing the time higher would worsen the surface [17] . Electropolishing temperature that resulted in lower roughness parameters and minimized the possibility of bacterial attachment was identified [18] .…”