POTENTIODYNAMIC AND XPS STUDIES OF X10CrNi18-8 STEEL AFTER ETHYLENE OXIDE STERILIZATION

An innovative development in the treatment of heart, blood and vascular-system diseases using low-invasive techniques led to a development of new forms of tools (among other devices: cardiologic guide wires) made of the X10CrNi18-8 steel. The authors of this study made an attempt to evaluate the impact of one of the medical sterilisation methods, i.e., the ethylene oxide sterilisation of a wire made of the X10CrNi18-8 steel after electrochemical polishing and chemical passivation. One of the basic criteria for deciding about the suitability of a specific material for a vascular tool is the proper corrosion resistance in a blood environment. It is directly connected with the chemical composition of the surface layer. Therefore, an evaluation was made on the basis of pitting-corrosion tests and the tests of the chemical compositions of the surface layers by means of the XPS method. The samples were subjected to the tests before and after the ethylene oxide sterilisation. The obtained results explicitly prove that the chemical-passivation process of the X10CrNi18-8 steel improves its resistance to corrosion in a blood environment. The resistance is higher due to the creation of a thin passive layer, mainly built of Fe2O3 and Cr2O3 on the surface, which was proved during the XPS tests. Next, the sterilisation in ethylene oxide had a favourable influence on the electrochemical properties of the X10CrNi18-8 steel, irrespective of the way of surface preparation. The presence of the alloying elements in the oxidised form was also detected in the surface layer, contributing to the improvement of the corrosion resistance in contact with the blood.