engleski

IMPROVEMENTS OF BIOCOMPATIBILITY OF AUSTENITIC STEEL ALLOYED WITH NITROGEN BY POTENTIODYNAMIC CYCLIZATION

Passivation of stainless steel implants is a common procedure used to increase their biocompatibility [1]. Cyclic potentiodynamic polarization, as a surface treatment method, has been reported as an efficient method to modify the chemical and electronic properties of passive films on austenitic stainless steels [2, 3]. In the present study the passive electrode of austenitic stainless steel alloyed with nitrogen (ASS N25) was modified by the cyclic linear potentiodynamic polarization (CLPP) method in a NaNO3 solution and the effect of CLPP on the barrier and semiconducting properties of the passive film was investigated in physiological solutions using electrochemical impedance spectroscopy (EIS) measurements and Mott-Schottky (M-S) analysis. The results obtained have showed that CLPP significantly improve the pitting and general corrosion resistance of stainless steel in chloride containing solutions. A thick and compact passive oxide film with a roughness texture at a nano-scale offers up to 98% relative protection efficiency against general corrosion in physiological solutions. The conversion of the type of semiconductivity from n to p takes place in the pitting susceptible region of the passive film. Such a semiconductor p-n junction (Schottky barrier) generates a high potential barrier for electrons in the passive film, i.e., it increases the polarization resistance of the passive film.

austenitic steel; biocompatibility

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