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

3. Results

Carried out electrochemical tests in artificial urine showed differential the pitting corrosion resistance of samples of steel of 1.4404 with different degree of strain hardening. The corrosion potential for all investigated samples established after 30 minutes.

Average value of corrosion potential for wire rod with diameter of 5,5mm was at the level of Ecorr=+65mV, and average value of breakdown potential was at the level of Eb=+404mV. The change of direction of sample polarization did not cause repassivation of the surface of samples – figure 1. The value of the corrosion current density was icorr=0,04A/cm2 and the value of polarization resistance was Rb=587,27kcm2. The investigations showed that average value of corrosion potential for wire of diameter 2,0mm was Ecorr=-3mV and average value of breakdown potential was Eb=+388mV. The change of direction of sample polarization did not cause repassivation of the surface of samples – figure 2.The value of the corrosion current density was icorr=0,04A/cm2 and the value of polarization resistance was Rb=668,19kcm2.

Average value of corrosion potential for wire of diameter 1,35mm was Ecorr=-143mV, and value of breakdown potential was Eb=+300mV.The value of the corrosion current density was icorr=0,07A/cm2 and the value of polarization resistance was Rb=370,68 kcm2. The figure 3 shows results for wire of diameter 1,35mm. Hysteresis loop in the diagram signals initiation and development of corrosion processes. Repassivation took place on average with the value of potentials of Erp=+100mV.

Table 3 shows results of pitting corrosion resistance of samples of Cr-Ni-Mo steel with differential degree of strain hardening.