The effect of different cathodic potentials applied to the X70 pipeline steel immersed in acidified and aerated synthetic soil solution under stress using a slow strain rate test (SSRT) and electrochemical impedance spectroscopy (EIS) was studied. According to SSRT results and the fracture surface analysis by scanning electron microscopy (SEM), the steel susceptibility to stress corrosion cracking (SCC) increased as the cathodic polarization increased (Ecp). This behavior is attributed to the anodic dissolution at the tip of the crack and the increment of the cathodic reaction (hydrogen evolution) producing hydrogen embrittlement. Nevertheless, when the Ecp was subjected to the maximum cathodic potential applied (−970 mV), the susceptibility decreased; this behavior is attributed to the fact that the anodic dissolution was suppressed and the process of the SCC was dominated only by hydrogen embrittlement (HE). The EIS results showed that the cathodic process was influenced by the mass transport (hydrogen diffusion) due to the steel undergoing so many changes in the metallic surface as a result of the applied strain that it generated active sites at the surface.
In the present research work, the influence of heat treatment on the corrosion behavior of a supermartensitic stainless steel (SMSS) in sour solution (H2S gas was replaced by sodium thiosulfate) was studied using polarization curve electrochemical techniques (CP) and Electrochemical Impedance Spectroscopy (EIS), along with microstructural characterization using optical microscopy and X-ray diffraction (XRD) measurements. The CP results revealed that the samples subjected to quenching and tempering process exhibited the formation of a more protective corrosion product layer. However, the EIS results showed that this layer accelerated the corrosion process as immersion time increased. Finally, according to XRD and electrochemical test results, the lower the percentage of volume fraction of retained austenite in the microstructure of SMSS, the lower the corrosion resistance.
In the present work, the compound 3´-(2,6-dimethoxybenzoyl)-benzyl 2,6-dimethoxybenzoate (RM4) was evaluated for its ability as a corrosion inhibitor in a 3% chloride medium and using an API 5L X70 steel working electrode. The electrochemical system was evaluated by electrochemical techniques such as polarization curves (CP) and electrochemical impedance spectroscopy (EIS), finding through the values obtained in polarization curves that the efficiency of the inhibitor at 50 ppm reached 73.2% against the corrosion phenomenon. The inhibition kinetics study shows that the evaluated organic compound maintains its protection against corrosion in a period of 120 hours of immersion.
In the present research work, the evaluation of a non-ionic gemini surfactant derived from palm oil named bis(2-((2-palmitoamidoethyl) amino) ethyl) 1H-imidazole-4,5-dicarboxylate as an ecological corrosion inhibitor of X100 steel immersed in NaCl solution at 3.5% saturated with carbon dioxide (CO2) was analyzed. The electrochemical tests performed by Polarization Curves (PC) and Electrochemical Impedance Spectroscopy (EIS) showed that the efficiency of the inhibitor increased according to the increase in the concentration of the inhibitor. Likewise, the EIS results showed that the inhibitor performance increased as the exposure time elapsed.
The ASTM A36 structural steel was evaluated with the electrochemical techniques, Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS) and Electrochemical Noise (EN). The techniques were applied to the bare steel substrate, coated, and coated with the addition of SiO2 nanoparticles (NP). The applied coating was a commercial epoxy of two layers. Stöber method was used to obtain the NP and were characterized with X-Ray Diffraction. A coating improved was obtained in the first day of immersion, according to EIS results, that it shows higher impedance compared with the coating without NP. Moreover, with the RE it was possible to observe that the NP reinforced coating showed a better anticorrosive performance, having a localized and mixed corrosion morphology.
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