Corrosion resistance of wires of cr-ni-mo steel used in endourology cd.

4. Conclusion

Potential-dynamic tests carried out on artificial urine supplied information about corrosion resistance of austenitic steel Cr-Ni-Mo with various degree of strain hardening. Comparative analysis of anodic polarisation curves showed that wire strain hardening influences their course. It is the evidence of various corrosion resistance of drawn wire made of 1.4404 steel. Together with the increase in degree of strain hardening of steel, decrease in corrosion potential and breakdown potential value was observed as well as the increase in passivation current value. These phenomenons are not favourable. Together with the increase in strain hardening of steel, decrease in corrosion potential Ecorr was observed, from the value of Ecorr=+65mV for wire with diameter of 5,5mm to the value of Ecorr=-143mV for the wire with diameter of 1,35mm. Together with the increase in strain hardening of steel, decrease in breakdown potential Eb was observed, from the value of Eb=+442mV for wire with diameter of 5,5mm to the value of Eb=+300mV for the wire with diameter of 1,35mm. Figure 4 shows results.

It was ascertained that polarization resistance did not tend to decrease its value together with the increase in steel strain hardening. Its value was diversified and went within the range from Rp=114,17kΩcm2 for 1,45mm wire to Rp=688,19kΩcm2 for 2,0mm wire. Value of corrosion current density was diversified and went within the range from icorr=0,23A/cm2 for 1,45mm wire to from icorr=0,039A/cm2 for 2,0mm wire. Value of corrosion rate for wire with diameter of 1,45mm was corr.=2,61m/year and the value for wire with diameter of 2,0mm was corr.=0,44m/year. Figure 5 shows results.

Test results show that corrosion potential, breakdown potential and passivation current are connected with wire strain hardening. There was no evidence of the influence of strain hardening on other tested factors (polarization resistance, corrosion rate, corrosion current density). Their value may be dependent on presence of moles of chloride ions in the solution of artificial urine. Chloride ions cause passive properties disappear. They can also prevent creation of passive layers on iron, chrome and nickel.

The authors: Katarzyna KULAK, Piotr NADBORSKI, Anna SOŁTYSEK, Witold WALKE

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