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.

Se propone la inclusión de perfiles de PET pretensados como fibras de refuerzo en elementos estructurales. Los perfiles de PET se colocan en una matriz de fibra unidireccional y bidireccional pretensada ligeramente que podría tener ventajas en miembros estructurales hechos de concreto en algunas aplicaciones especificas, por ejemplo, soporte estructural para barreras de seguridad vial. Una máquina universal se usa para probar perfiles de PET con diferentes anchos, nudos e incluso otras condiciones. Se elige el perfil de PET deseado y la mezcla de concreto se diseña según el codigo ACI. Los perfiles de PET pretensados se incluyen en moldes de madera con forma de vigas y, posteriormente, se estima la resistencia a la flexión. Finalmente, se presentan los resultados de las pruebas experimentales para perfiles de PET como refuerzo estructural de vigas hechas de concreto bajo flexión pura. Finalmente, se usa un modelo probabilístico para estimar la contribución de PET en términos de excedencia del módulo de ruptura.

In this work the corrosion kinetics of X80 steel immersed in synthetic seawater was analyzed using the electrochemical noise technique in static condition at room temperature and atmospheric pressure. An arrangement of three electrodes was used in an electrochemical cell, with two nominally identical working electrodes (X80 steel) and a saturated calomel electrode (SCE) as reference one. The results obtained were used to calculate the localization index (LI), which indicated that the corrosion process has a localized character. The optical micrographs confirmed the attack morphology of the corrosion process. Also, the corrosion rate values for X80 steel obtained from Noise Resistance (Rn) increase and decrease as exposure time elapses. The above is attributed to the rupture and subsequent regeneration of the corrosion products film adsorbed onto the metal surface.

In this work, electrochemical monitoring of stress corrosion cracking (SCC) behavior of a X70 steel in acidic synthetic soil solution during the slow strain rate test (SSRT) was performed by electrochemical noise (EN) using the conventional arrangement of symmetrical electrodes and electrochemical emission spectroscopy (EES) using the asymmetrical arrangement replacing the second working electrode for a platinum micro-cathode. The statistical method, fast Fourier transform, and discrete wavelet transform were used for analyzing the potential and current signals recorded by both arrangements. The results showed that EN arrangement was more effective to detect the crack initiation at a point close to yield strength despite stress-induced asymmetry in one of the electrodes. For the EES arrangement, the micro-cathode had a strong influence on the electrochemical noise of the current and potential under stress conditions. From the transient features, statistical parameters, and wavelet analysis, a discontinuous transgranular SCC mechanism was found. The resistance values obtained by EN measurements had better correlation with the electrochemical impedance spectroscopy results (EIS) than EES measurements.

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The damage caused by atmospheric pollutants, chlorides, and sulfates, is evident in historical metallic monuments. Therefore, it is vitally important to analyze these interactions to ensure adequate conservation. The electrochemical behavior was studied using Linear Polarization Resistance (LPR) and Electrochemical Impedance Spectroscopy (EIS) of quaternary bronze with an artificially formed patina with CuSO4 representing a historical metal exposed in the atmosphere and thus obtaining information about its degradation process during a determined time. The results show that charge and mass transfer processes were carried out by varying the resistances of the patinas during the weeks that they were exposed, reaching to observe a diffusive and metastable process due to the formation of corrosion products that lead to an increase in the resistance of charge transfer.

In the present work, contribution of supplementary cementitious materials (SCM) such as sugarcane bagasse ash (SCBA) and fly ash (FA) in the reduction of the corrosion phenomenon in AISI 1018 carbon steel as reinforcement during 24 hours of concrete setting was studied. The design of ternary concrete systems was carried out according to ACI 211.1 method. Ash percentages were 10 and 30% of SCBA and FA combined. During the electrochemical study, corrosion potential (Ecorr ) and electrochemical noise (EN) of AISI 1018 carbon steel was monitored. Time series of current and potential, as well as the corrosion current density (icorr), noise resistance (Rn), localization index (LI) and corrosion rate (Vcorr) were analyzed. Results show that concretes added with SCBA and FA presented a better anticorrosion behavior, especially ternary concrete system added with 10% of combined ash, corrosion rate decreased 55% against the reference concrete.

An electrochemical study of stress corrosion cracking (SCC) of API X70 steel in a simulated soil solution at different pH values (3, 8 and 10) was carried out. The stress conditions were implemented by slow strain rate stress test (SSRT) and the SCC process was simultaneously monitored by electrochemical impedance spectroscopy (EIS). Fracture surface analysis and corrosion product analysis were performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The results show that the susceptibility to SCC was higher as the pH decreases. In the acid solution, hydrogen evolution can occur by H+ and H2CO3 reduction, and more atomic hydrogen can diffuse into the steel, producing embrittlement. EIS results indicated that the anodic dissolution contributed to SCC process by reducing the charge transfer resistances during the SSRT test. While SEM micrographs shown a general corrosion morphology on the longitudinal surface of samples. At higher pH (pH 8 and pH 10), the SCC susceptibility was lower, which it is attributed to the presence of corrosion products film, which could have limited the process. Using the angle phase (φ) value it was determined that the cracking process started at a point close to the yield strength (YS).