Study of the correlation between corrosion resistance and semi‐conducting properties of the passive film of AISI 316L stainless steel in physiological solution

Abstract

In this work the corrosion resistance of AISI 316L biomedical stainless steel was assessed through electrochemical impedance spectroscopy (EIS) measurements in Hanks' solution at 37 °C. Specimens were immersed in the electrolyte during 21 days. Semi‐conducting properties of the passive film naturally formed on the surface of the metallic material during the test were evaluated through the Mott–Schottky approach. The aim was to investigate the correlation between corrosion resistance and semi‐conducting properties in the physiological solution. The corrosion resistance was found to decrease with the immersion time. The density of defects in the passive film increased accordingly as indicated by the Mott–Schottky plots. The passive film presented a semi‐conducting behavior with a duplex character. Above the flat band potential the behavior was typical of an n‐type semiconductor whilst below such value it was typical of a p‐type semiconductor. The results from EIS measurements and Mott–Schottky were in good agreement, suggesting that the corrosion resistance of biomedical stainless steels may be associated with the semi‐conducting properties of the passive films formed during immersion in physiological medium.

Passive films on metallic biomaterials under simulated physiological conditions

“…[75][76][77][78] In other cases, however, the spectra could be fitted with a dual R-CPE circuit representing the bilayer type of oxide film composed of an inner, barrier layer and an outer, porous layer. 15,74 The resistance of the inner layer in each case was up to three orders of magnitude greater than that of the outer layer.…”

“…Later work on 316L stainless steel in Hanks solution (apparently aerated) likewise showed an increase in the inner layer resistance after one week of immersion . The resistance was then found to decrease, however, as the immersion time was increased to three weeks.…”

“…The passive behavior of 316, 316L, and 316LVM stainless steel in simulated physiological solutions has been the subject of several EIS studies . In some cases, the impedance spectra could be fitted using a single R‐CPE equivalent circuit, where the parallel resistance was treated as the passive film resistance or the charge transfer resistance .…”

“…In some cases, the impedance spectra could be fitted using a single R‐CPE equivalent circuit, where the parallel resistance was treated as the passive film resistance or the charge transfer resistance . In other cases, however, the spectra could be fitted with a dual R‐CPE circuit representing the bilayer type of oxide film composed of an inner, barrier layer and an outer, porous layer . The resistance of the inner layer in each case was up to three orders of magnitude greater than that of the outer layer.…”

“…The passive behavior of 316, 316L, and 316LVM stainless steel in simulated physiological solutions has been the subject of several EIS studies. 15,[74][75][76][77][78] In some cases, the impedance spectra could be fitted using a single R-CPE equivalent circuit, where the parallel resistance was treated as the passive film resistance or the charge transfer resistance. [75][76][77][78] In other cases, however, the spectra could be fitted with a dual R-CPE circuit representing the bilayer type of oxide film composed of an inner, barrier layer and an outer, porous layer.…”