J. Przondziono

Electrochemical investigations of Cr-Ni-Mo stainless steel used in urology

The influence of chemical passivation process on physical and chemical characteristics of samples made of X2CrNiMo 17-7-2 steel with differentiated hardening, in the solution simulating the environment of human urine was analysed in the study. Wire obtained in cold drawing process is used for the production of stents and appliances in urological treatment. Proper roughness of the surface was obtained through mechanical working - grinding (Ra = 0,40 μn) and electrochemical polishing (Ra = 0,12 μn). Chemical passivation process was carried out in 40% solution of HN03 within 60 minutes in the temperature of 65°C. The tests of corrosion resistance were made on the ground of registered anodic polarisation curves and Stern method. For evaluation of phenomena occurring on the surface of tested steel, electrochemical impedance spectroscopy (EIS) was applied.

Corrosion resistance of premodeled wires made of stainless steel used for heart electrotherapy leaders

The purpose of the study is to evaluate resistance to electrochemical corrosion of wire made of X10CrNi18-8 stainless steel designed for use in cardiology treatment. The influence of strain formed in the premodeling process and methods of wire surface preparation to corrosive resistance in artificial plasma solution were analysed. Wire corrosion tests were carried out in the solution of artificial plasma. Resistance to electrochemical corrosion was evaluated on the ground of recorded curves of anodic polarization by means of potentiodynamic method. Potentiodynamic tests carried out enabled to determine how the resistance to pitting corrosion of wire changes, depending on strain formed in the premodeling process as well as on the method of wire surface preparation. For evaluation of phenomena occurring on the surface of tested steel, electrochemical impedance spectroscopy (EIS) was applied. Deterioration of corrosive properties of wire along with the increase in the formed strain hardening was observed.

Electrochemical Behaviour of Stainless Steel Wire for Urology

The study presents results of pitting corrosion tests and analysis of chemical composition of X2CrNiMo 17-12-2 steel surface layer with diversified strain hardening and the method of surface preparation after 30-day exposure to artificial urine. Samples with electrochemically polished as well as with electrochemically polished and chemically passivated surface were selected for the tests. Electrochemical passivation was applied in order to obtain extremely smooth surface (Ra0.16 m). Pitting corrosion tests were performed by means of potentiodynamic method, where analysis of chemical composition of the layer formed on the steel surface was conducted using X-ray photoelectron spectroscopy (XPS). The tests were carried out in order to determine suitability of X2CrNiMo 17-12-2 steel with modified surface and diversified strain hardening for production of wire used in urology.

Impedance spectroscopy study of the electrochemical corrosion of steel wire used in cardiologic leaders

The study presents the results of tests of electrochemical corrosion resistance of wires made of stainless steel X10CrNi18-8 for guides used in invasive cardiology. Measurements were made in artificial blood plasma solution by means of electrochemical tests system VoltaLab®PGP201. On the ground of the registered anodic polarisation curves, factors that characterise electrochemical corrosion resistance, i.e..: breakdown potential, polarisation resistance and corrosion current density, have been described. In order to evaluate phenomena that take place on the surface of the tested steel. Electrochemical Impedance Spectroscopy was employed. Measurements were made with the measurement system AutoLab PGSTAT 302N equipped with FRA2 (Frequency Response Analyser) module. During the tests, impedance spectra of the system were made and obtained data was matched to the equivalent circuit. Moreover, the effect of strain in the drawing process and the way of wire surface preparation on the resistance to electrochemical corrosion.

Steel Strips Flattening in Ball Rolling Mill

An effective and efficient production method of narrow and thin strips made of steel, non-ferrous metals and their alloys is wire flattening in a ball rolling mill. In this device cylindrical rollers have been replaced with balls of diameter ca. 15 mm. Proper selection of deformation process parameters enables to obtain strips with the required geometrical characteristics. Experimental planning method was applied to evaluate the influence of flattening process technological parameters on strip geometrical features. Statistical analysis enabled to determine mathematical models of stainless steel 5XCrNi18-10 strips flattening. It was established that strip widening depends on ball roughness, draft applied, relation of wire diameter to ball diameter, back-tension stress. Strips flatness depends on draft applied. It was observed that strips feature uniform thickness over their width, parallel flat surfaces, narrow dimensional tolerance, high quality surface and naturally rounded edges.

Determination of the flow curves of austenite steel wire in the drawing process

Flow curves enable to predict the response of material during metal forming processes. To establish properly the magnitude of flow stress, precise determination of the true stress from a tensile test is necessary. Calculation of true stress corresponding to the proof strength made it possible to determine the flow curves and select the appropriate flow stress equation for the tested drawn wires.

Resistance to Electrochemical Corrosion of Extruded Magnesium Alloy AZ31

The purpose of the study was evaluation of electrochemical corrosion resistance of extruded magnesium alloy AZ31. Corrosion tests were performed in NaCl solutions featuring chloride ions concentration from 0.01 to 2 M NaCl. Potentiodynamic tests enabled to register anodic polarisation curves. Immersion tests were performed in NaCl solution and time 1-5 days. Electrochemical impedance spectroscopy (EIS) was used to evaluate phenomena that take place on the surface of the tested alloy. Impedance spectra of the system were made in the tests, and obtained measurement data was matched to the equivalent system. The results of all performed tests prove explicitly deterioration of corrosion properties of extruded magnesium alloy AZ31 with the increase of molar concentration of NaCl solution. Options of magnesium alloy AZ31 application in aircraft and automotive industry are connected with the need for application of protective layers on elements made of the tested alloy.

Resistance to Electrochemical Corrosion of Extruded Magnesium Alloy AZ61

The purpose of the study was the evaluation of the electrochemical corrosion resistance of extruded magnesium alloy AZ61 in solutions with concentration of 0.012 M NaCl. Resistance to electrochemical corrosion was evaluated on the ground of registered anodic polarisation curves by means of potentiodynamic method. Immersion tests were performed in NaCl solution and time periods of 1-6 days. Scanning microscopy was used to obtain images of the alloy microstructure after immersion tests. Electrochemical impedance spectroscopy was used to evaluate phenomena that take place on the surface of the tested alloy. The results of all performed tests prove explicitly deterioration of corrosion properties of magnesium alloy AZ31 with the increase of molar concentration of NaCl solution. It was found that irrespective of molar concentration of NaCl solution, pitting corrosion can be detected on the surface of the tested alloy. Test results prove that it is necessary to apply protective layers on elements made of the tested alloy.

Influence of the Type of Medical Sterilisation on Electrochemical Properties of Passive Layer Created on X10CrNi 18-8 Steel

The study presents results of impedance tests performed for wires made of X10CrNi 18-8 steel after electrochemical polishing and chemical passivation, subject to medical sterilisation with pressurised water steam or ethylene oxide. In order to determine the impact of sterilising agent on electrochemical characteristics of the passive layer, impedance measurements were made. Measurements were made with application of measurement system Auto Lab PGSTAT 302N equipped with FRA2 (Frequency Response Analyser) module. Impedance spectra of the system were determined in the tests and data obtained in the measurement was matched to the equivalent system. It made the ground for determination of numerical values of resistance and capacitance of the analysed systems. Impedance spectra of the tested system are presented in the form of Nyquist diagrams for various values of frequency, and as Bode diagrams. On the ground of performed test it was explicitly proved that application of steam sterilisation and sterilisation with ethylene oxide of wires made of X10CrNi 18-8 steel after chemical passivation used for urological guide wires has a favourable impact on their electrochemical characteristics.

Forecasting of Corrosion Properties of Steel Wires for Production of Guide Wires for Cardiological Treatment

The study presents evaluation of the influence of strain in drawing process and of surface modification on resistance to electrochemical corrosion of wires made of stainless steel for production of guide wires used in invasive cardiology. The results of static tensile test enabled us to determine the course of flow curve of wires made of X10CrNi 18-8 steel as well as mathematical form of flow stress function. Resistance to electrochemical corrosion was evaluated on the ground of registered anodic polarisation curves by means of potentiodynamic method. The tests were performed in solution simulating human blood on samples that were electrolytically polished and samples that were polished and then chemically passivated. Exemplary anodic polarisation curves were given. It was proved that with the applied strain, corrosion properties decrease. It was found that chemical passivation improves wire corrosion characteristics. Statistical analysis showed that there is a significant dependence between corrosion properties (polarisation resistance ) and strain applied in drawing process. Functions that present the change were selected. The issue is of importance to guide wire manufacturers because application of the suggested methodology will enable us to forecast corrosion characteristics of wire with the required strength drawn with the applied strain.