Effect of tensile stress on corrosion behavior of 13Cr martensitic stainless steel

Abstract

Tubes in deep wells are subjected to the mixed effects of the environment and stress and thus suffer many failures. Therefore, studying the corrosion of materials under stress deformation is necessary. This paper aims to investigate the effect of applied tensile stress on the dissolution of passive film and the repair mechanism of L80-13Cr martensitic stainless steel in solution of 80 g·L-1 sodium chloride. Electrochemical tests were employed for measurements, where the main test measurements include open circuit potential (OCP), electrochemical impedance spectra (EIS), and potentiodynamic polarization tests. Contact angle measurement was combined with microscopic morphology analysis (Zoom stereo microscope) to investigate the surface activity. The test results show that there is the positive relation between applied tensile stress and the passivation characteristic of L80-13Cr martensitic stainless steel. Increase in the applied tensile stress negatively shifts the OCP value of L80-13Cr martensitic stainless steel, decreases the electron transfer resistance (Rt) and polarization resistance (Rp), and increases the rate of reaction; however, the passivation region significantly reduces, the passivation current density (Ecorr) increases, and the self-corrosion current density decreases, which forms at a high potential. The results of contact angle test and microscopic morphology analysis show that the applied tensile stress reduces the surface contact angle and promotes the pitting of L80-13Cr martensitic stainless steel. Applied tensile stress can increase the surface energy of L80-13Cr martensitic stainless steel, promote the dissolution of the passivation film, and inhibit the regeneration of the passivation film; thus, it can deteriorate the corrosion resistance of materials.

Keywords

• 13cr stainless steel
• tensile stress
• passivation characteristic
• surface activity