In the last years, electrochemical noise (EN) has demonstrate that is capable of detect the initiation of cracks during the slow strain rate tests (SSRT). In this research, EN has been used as a tool to detect stress corrosion cracking (SCC) in low carbon steel (X52) exposed to a synthetic soil solution called NS4 at room temperature with pH of 5, 8 and 10. The electrochemical potential and current noise were measured simultaneously during SSRT. Relation between EN and SCC process was analyzed. EN readings of current consisted of transients with high intensity and frequency during all SSRT tests. EN readings of potential at the maximum strength (UTS) and before fracture, increase intensity and amplitude of the transients, attributed to beginning of cracking. Localized index (LI) values indicate a mix corrosion type (general and localized corrosion) during SSRT tests. According to SCC index obtained from mechanical properties, it is clear that X52 steel has low SCC susceptibility. Scanning electron microscopy (SEM) observations were carried out in the fracture surface and longitudinal sections. The specimens tested in NS4 solution with pH 5 were the most likely to present SCC, additionally in this condition a brittle fracture with transgranular appearance was observed.

In this work, API X-65 pipeline steel non-conventionally heat treated, to enhance its mechanical resistance, was welded using the Metal Inert Gas (MIG) process with and without the application of low intensity axial magnetic fields (6 mT). Microstructural and mechanical characterization of the welds revealed that the use of the magnetic field during welding improved the toughness of the welds and therefore increased their mechanical strength. Failure of the welds occurred far from the weld beads. The electromagnetic stirring of the weld pool significantly reduced the levels of porosity in the weld beads and favored columnar grain growth due to the ferromagnetic nature of the base metal and filler wire. Impact toughness was also improved from 120 to 266 J. Hardness values measured across the welds indicate that the use of the magnetic field during welding yields welds suitable for withstanding sulphide stress cracking.