Effect Of Cathodic Polarization Research Articles

Influence of cathodic polarization on stress corrosion cracking susceptibility of 35CrMo steel for high strength bolt in simulated deep-sea environment

The effect of cathodic polarization on stress corrosion cracking (SCC) of 35CrMo steel for high strength bolt in the simulated deep-sea environment has been studied. The results show that 35CrMo steel has a higher SCC sensitivity at open circuit potential in the simulated deep-sea environment than that in the shallow seawater. With potential negatively shifted to −750 mV, 35CrMo steel presents the lowest SCC sensitivity. And the SCC susceptibility is increased significantly with the further negative shift of potential because of the intensive hydrogen evolution. When the potential is below −950 mV, hydrogen embrittlement with hydrogen-enhanced-plasticity mediated decohesion should be the dominant SCC micro-mechanism.

Determination of the residual life of the pipe metal under conditions of corrosion fatigue

This paper presents a method for calculating the residual metal life of pipelines with crack-like defects. The results of corrosion and fatigue tests of ordinary grade structural steel VSt3sp, widely used in the oil and gas industry, are presented. The work carried out studies on the effect of cathodic polarization on the cyclic crack resistance of VSt3sp steel under the influence of a carbonate-bicarbonate medium.

Effect of Cathodic Polarization on SCC Behavior of a X52 Pipeline Steel in Service for 20 Years

Effect of Cathodic Polarization on SCC Behavior of a X52 Pipeline Steel in Service for 20 Years

Plasma electrolytic oxidation of tantalum in an aluminate electrolyte: Effect of cathodic polarization and frequency

The effect of cathodic polarization on plasma electrolytic oxidation (PEO) of the refractory metal of tantalum is investigated in 10 g/l NaAlO2+2 g/l KOH under 1000 and 100 Hz. Ceramic coatings are formed under various cathodic-to-anodic current densities ratios (R = jc/ja) of 0, 0.6, 1.3 and 2.3. For PEO under 1000 Hz, the plasma discharges intensify with the increase of R from 0 to 1.3, with optical emission from Ta being detected at later stage of PEO under cathodic polarization. However, excessive R ratio of 2.3 has caused early extinguishment of the plasma discharges. Correspondingly, thicker coatings are formed as the R ratio increases from 0 to 1.3, and the coating under R = 1.3 exhibits a most porous outer layer. A thin and compact coating is formed under R = 2.3. It is also found that the application of cathodic polarization increases the Na content in the resultant coatings, with a new crystalline phase NaTaO3 being formed under R = 2.3. Cathodic polarization also decreases the corrosion resistance of the coatings. Surface wettability tests show that the coatings formed under R = 1.3 are the most hydrophilic. PEO under 100 Hz shows some differences in discharge and coating formation. Larger sized discharges are also observed at the later stage under R = 0.6, but Ta species are detected at a delayed time. For the R values of 1.3 and 2.3, patches of soft sparking occur on the sample surface, leading to non-uniform coatings. This study shows that both cathodic polarization and frequency significantly affect the PEO process. Moreover, compared with the PEO of Al, tantalum responds quite differently to cathodic polarization. Mechanisms of coating formation have been illustrated: Protons and other cations are attracted by cathodic electric field into the coatings, where they undergo a series of reactions to significantly affect the PEO behaviors.

Corrosion Behavior of Alkyd-Resin-Coated Carbon Steel under Cathodic Polarization in Both Static and Flowing Seawater

The effect of cathodic polarization on the corrosion behavior of alkyd-resin-coated carbon steel with an artificial coating defect was researched using a wire beam electrode (WBE) and electrochemical impedance spectroscopy (EIS) in both static and flowing simulated solutions. The microscopic morphology and chemical structure of the organic coating were characterized by scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR) to reveal the degradation mechanisms of organic coatings under different polarization potentials. The study found that the failure process of the alkyd coating could be accelerated by cathodic polarization. After 312 h of immersion, the impedance under −1100 mV was one order of magnitude lower than that under the open-circuit potential (OCP). The coating delamination became serious with the negative shifting of polarization potential, and the delamination area ratio under −1100 mV in both static and flowing seawater rose to 23% and 14%, respectively. Interestingly, the flowing condition of the immersion solution that combined with cathodic polarization exhibited a synergistic effect, which could accelerate (in the earlier stage) and then alleviate the delamination of the coating. Furthermore, the results showed that both the diffusion of the corrosion particles and the anodic dissolution reaction of the metal could be significantly affected by cathodic polarization and the flowing condition of the solution, which provides a possible approach to gain insight into the delamination of organic coating.

Effect of cathodic polarization on stress corrosion cracking susceptibility of 35CrMo steel for Class 12.9 fasteners in seawater

The effect of cathodic polarization on stress corrosion cracking (SCC) of 35CrMo steel for high strength fasteners in seawater was investigated by electrochemical measurement, slow strain rate tensile tests and fracture analyses. The results demonstrated that the 35CrMo steel with a typical tempered martensite microstructure has some SCC susceptibility at the open circuit potential (OCP), and the susceptibility decreases as the potential is shifted negatively until −850 mV vs. SCE, at which the steel presents the lowest SCC susceptibility due to the inhibition of anodic dissolution (AD) and little hydrogen evolution. The SCC sensitivity increases significantly as the applied potential further shifts negatively because of intensive hydrogen evolution. The fractures are transgranular at all potentials. AD is considered to be the main cracking mechanism at OCP, while hydrogen embrittlement becomes dominant at the potential below −850 mV vs. SCE.

Influence of polarization on the electrochemical activity of La2–xCaxNiO4+δ electrodes in contact with Ce0.8Sm0.2O1.9 electrolyte

The effect of electrode polarization on the electrochemical activity of La2NiO4+δ and La1.9Ca0.1NiO4+δ electrodes in contact with the Ce0.8Sm0.2O1.9 electrolyte is studied by impedance spectroscopy. It is found that anodic polarization facilitates electrode reaction for both electrodes leading to significant decrease in the polarization resistance. The effect of cathodic polarization differs between the electrodes: the polarization resistance of La2NiO4+δ electrode slightly increases, while the polarization resistance of La1.9Ca0.1NiO4+δ electrode strongly decreases with the increase in the applied potential. It is established that in all cases the polarization mostly affects the low-frequency stage of the electrode reaction, connected with oxygen surface exchange and diffusion. The surface state of the samples after exposure under polarization is studied by X-ray photoelectron spectroscopy. Correlations between electrochemical activity of the electrodes and the changes in their surface composition under polarization are discussed.

Corrosion of X65 steel by Pseudomonas sp. in planktonic and sessile states and inhibition effect of cathodic polarization

In harsh marine environment, corrosion is a serious problem, among which microbiologically influenced corrosion is particularly common and complex. This work studied corrosion of X65 steel by planktonic and sessile iron oxidizing bacteria (IOB), i.e. Pseudomonas sp. isolated from coastal water of Qingdao, and inhibition effect of cathodic polarization. Results demonstrate that both the planktonic and sessile IOB caused the corrosion of X65 steel by promoting the oxidation of ferrous ions, but the contribution of sessile cells was far greater than that of planktonic cells. Cathodic polarization kills sessile cells on the metal surface and prevent attachment of IOB. With a negative shift of the cathodic potential, the inhibition effect was enhanced. Cathodic polarization altered interface properties of X65 steel, affecting adhesion and corrosion process of IOB cells. However, when X65 steel was sufficiently polarized to −1050 mV vs. SCE, IOB produced more extracellular polymeric substances to resist stimulation by an external electric field. Therefore, cathodic polarization could not completely remove sessile IOB cells, and pitting corrosion existed on the metal surface.

Hydrogen permeation through steel during cathodic polarization of lubricating oils in a modified Devanathan–Stachurski cell

In lubricated tribo-contacts, hydrogen ingress in steel is possible due to chemical reactions of lubricant components like base oils or additives, and/or contamination upon service particularly water, and/or corrosion processes, and/or electrostatic fields or current flow. Absorbed by the metal, atomic hydrogen may cause serious deleterious effects on the physical–chemical and mechanical properties, reducing the material’s ability to withstand the design loads. The present research work is focused on analyzing the influence of electric field on lubricating oils in contact with steel surface. In order to evaluate the possibility of atomic hydrogen generation and permeation into the steel under cathodic polarization of lubricating oils the electrochemical permeation technique developed by Devanathan and Stachurski is used. The input cell of a Devanathan–Stachurski set up is appropriately modified by realizing a very close distance between the working electrode (steel membrane) and a Pt counter electrode with the oil between. This significantly increases the sensibility of the set up and allows the application of larger voltage and higher temperature to enable hydrogen generation from lubricating oils. The complex effects of cathodic polarization, temperature, additives and presence of water in model lubricating oils on atomic hydrogen permeation into steel is discussed.

Effects of cathodic polarization on X65 steel inhibition behavior and mechanism of mixed microorganisms induced corrosion in seawater

The laws of cathodic polarization on bacterial growth, biofilm formation and effects on the corrosion process of X65 steel were investigated when sulfate-reducing bacteria (SRB) and iron-oxidizing bacteria (IOB) are mixed using surface analysis and electrochemical measurements. Results indicate that insufficient potentials could not inhibit the localized corrosion, but increased the metabolic activities of bacteria. Effective protection could be achieved when the potential was negatively shifted to − 1050 mV vs. SCE. The effects of cathodic polarization on the precess of biofilms formation were also investigated. The − 1050 mV vs. SCE polarization potential could inhibit the biological activity of sessile bacteria, destroy the biofilm structure and inhibit the corrosion process induced by each biofilm.

Effects of Cathodic Polarization on the Corrosion Behavior of X60 Pipeline Steel in a Simulated Soil Solution

The objective of this study is to investigate the relationship between the cathodic polarization, the evolution of hydrogen, and its effect on the formation of calcareous deposits on X60 pipeline steel in a simulated soil solution and its behavior at open‐circuit potential (OCP) after interruption of cathodic polarization. Electrochemical measurement (chronoamperometry, potentiodynamic polarization, OCP evolution, electrochemical impedance spectroscopy (EIS)), and surface characterization techniques are used. The time evolution of EIS spectra is examined. The results show that cathodic polarization favors the release of hydrogen, and weakens and/or prevents the formation of calcareous deposits on the steel surface. After stopping polarization, the corrosion kinetics is retarded for high cathodic potentials, which could be due to the blocking of the surface by the adsorbed hydrogen.

Effects of Cathodic Polarization on X65 Steel Inhibition Behavior and Mechanism of Mixed Microorganisms Induced Corrosion in Seawater

Effects of Cathodic Polarization on X65 Steel Inhibition Behavior and Mechanism of Mixed Microorganisms Induced Corrosion in Seawater

ЗАКОНОМІРНОСТІ КОРОЗІЙНОГО РОЗТРІСКУВАННЯ ТРУБНОЇ СТАЛІ 10Г2ФБ У МОДЕЛЬНОМУ ГРУНТОВОМУ СЕРЕДОВИЩІ ЗА КАТОДНОЇ ПОЛЯРИЗАЦІЇ

Purpose. Investigate the regularities of corrosion cracking of 10G2FB steel under cathodic protection.Methodology. The following methods were used: slow strain rate, scanning electron microscopy, electrolytic hydrogenation, mass measurement.Results. The regularities of corrosion cracking of pipe steel 10G2FB in near neutral soil environment NS4 in the range of potentials from the corrosion potential to -1.2 V were investigated. According to the results of a complex of corrosion-mechanical, electrochemical and physical studies, it was found that with a shift in the cathodic polarization potential in the range of -0,75 V ® -0,95 V ® -1,05 V ® -1,2 V ® -0.95 V the coefficient of susceptibility of this steel to stress corrosion cracking KS increases correspondingly, 1,09 ® 1,11 ® 1,13 ® 1,26. The concentration of hydrogen which penetrating into steel at these potentials changes nonmonotonically: 0 ® 0 ® 0,057 ® 0,018 mol/dm3. The rate of residual corrosion with a potential shift in the series Еcor ® -0,75 V ® -0,95 V ® -1,05 V decreases first sharply, then slowly: 0.035 mm/year ® 0.005 mm/year ® 0.0009 mm/year ® 0.0004 mm/year, i.e. at high cathodic potentials, the applied polarization is spent on the decomposition of the aqueous electrolyte with the release of hydrogen, which penetrates into the steel and causes brittle cracking, which is confirmed by an increasing in the part of brittle fracture in the surface morphology of the specimens.Scientific originality. New results of fundamental research concerning the regularities of stress-corrosion cracking of ferrite-pearlite class steel of pipe assortment 10G2FB under conditions of cathodic protection in the range of potentials from the corrosion potential to -1.2 V have been obtained. It was revealed that a feature of the effect of cathodic polarization in the indicated range of potentials when assessing the tendency to stress corrosion cracking by the KS coefficient is an increasing in the relative narrowing and a decrease in the relative elongation, which generally indicates the embrittlement of the metal under the contact with corrosive medium and potential. Strength characteristics remain almost the same. The greatest tendency to stress-corrosion cracking is observed at a polarization potential of -1.0 V or more negative.Practical value. The developed methodology for a complex study of the regularities of stress- corrosion cracking was used for study of 10G2FB steel of the pipe assortment in a model soil environment NS4 under conditions simulating operating conditions. The new data obtained on the regularities of stress-corrosion cracking of steel will be useful for preventing the stress-corrosion cracking of main gas pipelines during operation.

Effect of Cathodic Polarization on Corrosion Behavior of X65 Steel in Seawater Containing Iron-oxidizing Bacteria

Effect of Cathodic Polarization on Corrosion Behavior of X65 Steel in Seawater Containing Iron-oxidizing Bacteria

Анализ влияния величины катодной поляризации на количество сорбированного водорода Al-Sm сплавом из электрохимических измерений

The effect of cathodic polarization on the rate of hydrogen sorption from an aqueous organic electrolyte on an Al-Sm alloy using the potentiostatic and potentiodynamic methods were studied. The obtained data allowed us to calculate the diffusion-kinetic characteristics of this process, such as the interstitial constant, diffusion constant CН √ D, constant current iconst, diffusion coefficient D and adsorption of hydrogen atoms G. The number of nuclei decreases, but their mass and radius increase in the potential range from –2.0 V to –2.4 V. The adsorption of hydrogen on the surface increases; which confirms that predominance of the discharge of hydrogen atoms occurs at more negative potentials according to the recombination mechanism.

Effect of cathodic polarisation on stress corrosion cracking behaviour of a Ni(Fe, Al)-maraging steel in artificial seawater

The effect of cathodic polarisation on stress corrosion cracking (SCC) behaviour of peak-aged Ni(Fe, Al)-maraging steel in artificial seawater was investigated. The steel shows better compatibility of strength and hydrogen embrittlement (HE) resistance than reported 18Ni-type maraging steels when potential is above −850 mV. This advantage stems from the abundant and evenly dispersed Ni(Fe, Al) nanoprecipitates. SCC occurs above −850 mV in a transgranular/intergranular-mixed manner involving a mechanics-dominant-anodic-dissolution-promoted mechanism and below −850 mV in an intergranular manner along parent austenite grain boundaries involving HE. For interpreting the HE mechanism, a novel model is proposed based on hydrogen-weakening interatomic bonds.

Hydrogen embrittlement of API 5L X65 pipeline steel in CO2 containing low H2S concentration environment

The basic corrosion mechanisms in CO2 environments are widely investigated and reported by scientific community. However, cracking failure mechanisms in CO2 environment or in environments where CO2 coexist with other gases need a better understanding. Cracking susceptibility of API 5L X65 in pure CO2 was recently reported and the basic mechanism was attributed to hydrogen embrittlement. The influence of hydrogen permeation and the detrimental effect of cathodic polarisation support the assumption of hydrogen embrittlement as the determining factor for the loss of plasticity and strength. The loss of strength of an API 5L X65 steel when CO2 and H2S coexist in the same environment is the focus of the present work. Hydrogen embrittlement (HE) and hydrogen induced cracking (HIC) of pipeline steels are failures modes expected to occur in CO2 with traces of H2S environments. The present work aims to approach the performance in laboratory of an API 5L X65 steel in CO2 with traces of H2S environment (slightly sour), using as baseline the performance of the material in pure CO2 environment (sweet), already reported. Hydrogen permeation and Slow Strain Rate Tests (SSRT) were carried out in CO2 environment containing low concentration of H2S. It was observed that traces of H2S in CO2 environment promote much more intense hydrogen permeation, much higher than in purely CO2 environment. Loss of ductility was also much more severe than in CO2 environment, with and without the influence of cathodic polarisation. Hydrogen generation enhancement promoted by traces of H2S in solution, corresponding to an average content of 21 ppm in solution, had a heavy effect on hydrogen embrittlement of the steel, confirmed by the lower ratio of reduction in area (RRA) and time to fracture in comparison with sweet service conditions.

The effect of cathodic polarization on the corrosion behavior of X65 steel in seawater containing sulfate‐reducing bacteria

AbstractSulfate‐reducing bacteria (SRB) are one of the main reasons for the accelerated corrosion of steel. Cathodic polarization has been reported as an effective and economic method against marine corrosion, including microbiologically induced corrosion. However, the interaction between cathodic polarization and microbial activity has not been well defined. In this study, a fluorine‐doped tin oxide electrode is used to study the effect of cathodic current on SRB cells. Fluorescence microscopy results clearly show that the attachment degree of SRB is dependent on the electric quantity and current intensity. The large electric quantity and high cathodic current (400 mA/m2 × 30 h) can effectively inhibit bacterial attachment and subsequent biofilm formation. Furthermore, the effect of cathodic potential on the corrosion behavior of X65 steel in the presence of SRB is systematically investigated. Results show that the impressed charges, the increase of pH, and the formation of calcareous deposits on the electrode surface at the cathodic potential of −1,050 mV/SCE inhibit the attachment of SRB. In turn, the presence of SRB also interferes with the electrochemical reactions that occur during the polarization process, thus increasing the cathodic current. The interaction between SRB‐induced corrosion and the process of preventing corrosion by various cathodic potentials is discussed.

Exploring the effect of cathodic polarization to mitigate CRUD deposition

Cathodic polarization is investigated as a technique for CRUD build-up mitigation in simulated primary pressurized water reactor conditions and accelerated flow. This investigation showed that the application of 3 V could induce a 67% reduction in surface deposition whilst 30 V cell voltage completely prevented the formation of surface deposits. This behavior can be rationalized considering the synergistic effect between the suppression of the electrokinetic component responsible for the CRUD build-up, and the hydrodynamic cleaning arising from the hydrogen evolution on the cathodically polarized surface.

A study of the electrochemical reactivity of titanium under cathodic polarization by means of combined feedback and redox competition modes of scanning electrochemical microscopy

The effect of cathodic polarization on the electrochemical behavior of the thin titanium dioxide film formed by anodic pretreatment over pure commercial titanium metal for biomaterial application was investigated in situ using scanning electrochemical microscopy (SECM). Quantitative information on the electron transfer rates (keff) at the titanium surface was obtained using the feedback operation of SECM with ferrocene-methanol (FcMeOH) as electrochemical mediator. An increase of keff values with the increase of the negative polarization was detected, a feature that correlates well with the decrease of titanium oxide resistance with increasing cathodic polarization observed using electrochemical impedance spectroscopy (EIS). In addition, SECM operation in the redox competition mode proved that hydrogen was absorbed in the surface oxide film leading to changes in conductivity and electrochemical reactivity.