Electrochemical Noise Analysis of the X70 Pipeline Steel under Stress Conditions Using Symmetrical and Asymmetrical Electrode Systems

Abstract

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.

Corrosion Resistance of Titanium Alloys Anodized in Alkaline Solutions

“…The low energy is related to passive systems, as is presented in Figure 6a for all samples except Ti-6Al-4V anodized in KOH and Figure 6b for all samples. Authors such as Carmona-Hernandez et al [65] suggest that the discontinuous process is like metastable pitting, relating that with this project, the different process is caused by a non-homogenous surface that induces the accumulation of energy in the first crystals of Ti-6Al-4V anodized in KOH. The TiO 2 generated on the surface was stable enough for the rest of the samples, and the nucleation of the localized process did not occur in this experiment's parameters.…”

Electrochemical Noise Measurements on Titanium Regarding Implant Applications

“…Those cracks can either proceed along grain boundaries (intergranular) or through the grains (transgranular). [ 26 ]…”

Data Mining Applied to the Electrochemical Noise Technique in the Time/Frequency Domain for Stress Corrosion Cracking Recognition

“…), are usually applied as key parameters to detect localized corrosion [48,56]. This is also applicable to a complex corrosive mechanism such as SCC [18]. Details of the main statistical parameter of the ENC and ENP time series investigated in this paper are reported in [14]; however, usually it is required to take a multiple variable approach on EN features, e.g., by using a neural network method [14], to discriminate the fundamental parameters and their correlation during the different and synergistic phases of the process.…”

“…In this concern, studies performed on stainless steel under various conditions [15,16] showed that on SCC tests, it may be feasible to quantify electrochemical current and voltage noise variations caused by the cyclical activation and propagation of cracks. In a lot of research activities [17][18][19], hydrogen embrittlement and the impact of the related evolved hydrogen bubbles on the EN transient was accurately investigated.…”