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    Effect of Tensile Stress on Pitting

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    Aim To investigate the relationship between tensile stress and pitting corrosion resistance of 2205 duplex steel at 40 and 60 respectively. Methods The potentiodynamic polarization behavior of 2205 duplex stainless steel tube in 3.5% NaCl solution below critical pitting temperature (40 C) and near critical pitting temperature (60 C) was analyzed under three kinds of tensile stresses of 0, 140 and 540 MPa, and the effects of different tensile stresses on the impedance characteristics of 2205 duplex steel were compared. Results Potentiodynamic polarization curves showed that pitting corrosion potential was stable at 140 MPa, breakdown potential was 0.7 and 0.8 V at 40 and 60 C, respectively, and pitting corrosion potential of duplex steel decreased from 0.9 V without stress to 0.3 V under 540 MPa tensile stress. Impedance analysis shows that all samples have a single impedance characteristic at 40 C, and the impedance value is larger, and the stress will reduce the impedance value. Under 60 C and open-circuit potential, 0 and 140 MPa have higher impedance under tensile stress, 540 MPa has impedance arc with pitting initiation under tensile stress, and 0 and 540 MPa exhibit pitting impedance under 60 C and 600 mV bias, while 140 MPa has higher impedance. The results of impedance spectroscopy equivalent circuit fitting combined with the surface micro-morphology of stainless steel tube show that no pitting corrosion occurs on the