Cathodic Protection Conditions Research Articles

Investigation on localized corrosion behavior of pipeline steel under AC interference in alkaline earth metal environment using wire beam electrode

The localized corrosion behavior of X65 steel under AC interference in alkaline earth metal environment was investigated using the detachable wire beam electrode (WBE). The AC/DC current distribution, electrochemical properties, and elemental distribution were traced through the WBE to characterize the localized corrosion behavior and mechanism. The results show that hydrogen evolution under high cathodic protection (CP) conditions leads to an uneven distribution of calcareous deposits, and areas not covered by calcareous deposits have higher JAC and Cl− concentrations. The synergistic effect of Fe3O4 dissolution reprecipitation process, hydrogen evolution and Cl− leads to severe localized corrosion.

Probing the efficiency and mechanism of hydrogen permeation inhibition in pipeline steel by organic inhibitors

A hydrogen economy will require the use of steel pipelines to transport and store hydrogen. Methods and materials are urgently needed to prevent the embrittlement of steel pipelines in hydrogen service. In this work, we show that hydrogen permeation into pipeline steel can be mitigated by organic inhibitors, as demonstrated by a typical organic inhibitor benzotriazole (BTA) under simulated X65 steel pipeline cathodic protection conditions. Electrochemical and surface analytical techniques were used to probe the efficiency and mechanism of hydrogen permeation inhibition. In particular, a novel multi-electrode array method was designed to probe the inhibitor film by measuring local impedance and hydrogen charging currents. The ability and efficiency of BTA to inhibit hydrogen permeation were found to be closely associated with the formation and coverage of inhibitor films on steel surfaces. A model is proposed to illustrate the mechanism of hydrogen permeation inhibition by organic inhibitors.

In situ and ex situ investigation on the product films evolution of pipeline steel under AC interference and high cathodic protection conditions

An in situ Raman measurement set-up coupled with AC interference and CP circuits was developed to provide more intuitive detection data for combined action AC and CP corrosion processes. Combined with XPS, AFM and other ex situ surface analyses and electrochemical tests, the evolution of composition, structure and electrochemical properties of surface film is studied. Initially, a passive film is formed on specimen surface, which undergoes successive redox processes. Eventually, the passive film evolves into magnetite and rust, and hydrogen evolution produces mechanical damage to rust layer. Based on this, the model for the evolution of AC corrosion is constructed.

REGULATIONS OF THE FORMATION OF PROTECTIVE POTENTIAL OF UNDERGROUND STEEL PIPELINES UNDER CONDITIONS OF HETEROGENEOUS ENVIRONMENT

In the work, the modeling of the distribution of the protective potential of electrochemical protection stations is performed by revealed functional dependencies. The initial conditions are adopted for a typical assortment of rolled metal used for underground gas supply. At the initial stage of modeling, the stochastic nature of the change in soil parameters is not taken into account. The distribution of the protective potential of the underground pipeline as a function of two variables (time and distance) showed the mutual influence of neighboring stations on the formation of protective zone. New dependences of the operating parameters of the electrotechnical complex of electrochemical protection on the set of variables characterizing the power source, the physical dimensions of pipeline and the alternative arrangement of active cathodic protection stations (CPS) were obtained. Experimental studies of the modes of electrochemical protection stations at the objects of the gas transportation system of Ukraine confirmed the adequacy of the proposed analytical models. References 16, Figures 3.

Protocols of data collection networks based on IEEE 802.15.4 radio channels in complexes for the protection of underground metal structures from electrochemical corrosion

Radio communication systems in telemetry and telemechanics systems of active electrochemical protection of underground metal structures are considered. The requirements for radio exchange systems for data collection networks from remote control and measuring points of cathodic protection stations are formulated. The analysis of the applicability of known exchange protocols based on the specifications of the IEEE 802.15.4 standard and its software add-ons for such networks is carried out and the need for the development of specialized network and channel layer protocols is justified. The results of the development of specialized network protocols of the application, network and channel levels that implement data exchange modes required for the collection networks under consideration while minimizing energy consumption are presented.

The significance of ferrous ion oxidation during corrosion of carbon steel in aerated near-neutral aqueous solutions

Numerical models were developed to investigate the significance of ferrous ion oxidation in carbon steel corrosion in near-neutral aerated aqueous solutions. The results demonstrated that the inclusion of ferrous ion oxidation improved the accuracy of pH predictions in deep crevices under cathodic protection and Evan's drop exposure conditions, closely matching experimental observations. The reaction rate for ferrous ion oxidation was found to be between 1 × 1014 and 2 × 1014 (mol/L)-2 atm−1 min−1. These findings highlight the importance of considering ferrous ion oxidation when modelling carbon steel corrosion in near-neutral aerated aqueous solutions.

Evaluation of pH variation in cathodic protection conditions by FEM simulation

AbstractCathodic protection is an electrochemical technique used to control the corrosion of metals. It does this by sending a proper amount of current equal to the current required by the cathodic processes at the protection potential. One of the chemical effects of cathodic protection is a local pH increase at the surface, which is an important factor in the reduction of corrosion rate, as carbon steel may work in a passive condition. In the present study, a tertiary current distribution finite element method model is introduced. A dynamic boundary condition is considered, by defining a Fe anodic Tafel slope as a pH function, and oxygen reduction reaction limiting current density as a function of available oxygen at the cathode surface. The model has been validated by direct pH measurement during a short‐term polarization test, and subsequently used to predict the pH and the available oxygen at the cathode surface for long‐term condition.

Optimization of the cathodic protection system for the main pipelines

This study investigated the multi-criteria task of optimizing the operating modes of cathodic protection stations (CPS), considering monitoring data, geological conditions at the pipeline installation site, climatic or seasonal changes, and other factors. The relevance of this research is associated with a comprehensive solution to the problem of increasing the durability and reliability of trunk pipelines to reduce accidents at their facilities by ensuring the efficiency of electrochemical protection (EChP) systems. The problems of existing EChP systems are analyzed, where the elimination of anode zones ("lack of protection") due to cathodic polarization is carried out without operational consideration of environmental conditions, as a rule, with a margin in terms of protective potential, which often leads to "overprotection", resulting in increased power consumption, gas formation on the metal surface, and detachment and wear insulation of pipelines. The aim of this research is to create a method for optimal regulation of the operation modes of the main pipelines and an adaptive electrochemical protection system that provides control and parameter management of cathodic protection stations, considering changes in external conditions on individual linear sections of main pipelines. Tasks: to develop an adjustment method for finding the effect of the CPS on the value of potentials at control points along the pipeline route; to develop a multicriteria optimization model for regulating the operation modes of the CPS; and to provide an example of testing the method of optimal regulation on the objects of the linear part of the existing main gas pipeline. The following results were obtained. A method is proposed for determining the effect of CPS operating modes on the value of potentials at control points in the mode of interrupting the protection current of other stations. An optimization model was formed according to the criterion of uniformity of the distribution of the protective potential "pipe-ground" along the pipeline route and according to the criterion of the minimum total protective current of all CPSs on a given section of the main pipeline. Conclusions. The scientific novelty of the results obtained is associated with the development of an original optimization method that allows scientifically determining the operation modes of the CPS to ensure the protection of the main pipeline both in time and length with reduced operating costs and adaptability to changes in climatic, seasonal, and geological conditions at the pipeline installation site. The effectiveness of the proposed approach is illustrated by the regulation of the parameters of the CPS based on the monitoring data of the section of the main gas pipeline of the oil and gas complex of the Republic of Kazakhstan.

Study on tide characteristics and mechanism of PSP in buried pipeline along the lake

The fluctuations of the Pipe-to-Soil Potential (PSP) in buried pipes are influenced by the geoelectric field induced by changes in the Earth's magnetic field, which can accelerate pipeline corrosion. Monitoring data of PSP along China's West–East Gas Pipeline near the lake indicates obvious tidal changes. This study proposes that the periodic movement of the conductivity boundary of the seepage area near the lake shore caused by tides is the fundamental cause of the tidal changes in PSP. The movement of the boundary changes the range of the H polarization of the geoelectric field, resulting in periodic changes in the PSP of the pipeline outside the seepage area. To investigate this mechanism, a dynamic boundary model of conductivity in the seepage area of Sailimu Lake in Xinjiang was established, and the characteristics of PSP at different distances from the boundary were analyzed using electromagnetic field finite element method and DSTL pipeline model. The study compared the simulation results of the model with the PSP data of the cathodic protection station and PSP monitoring station near Sailimu Lake, during a geomagnetic disturbance on September 23–24, 2016. The results of the study, as well as the corrosion of the test strips along the lake, verified the validity of the boundary change mechanism and model of the seepage zone. This study provides a theoretical basis for corrosion protection of pipelines near the lake’s edge.

Remaining fatigue life assessment of corroded mooring chains using crack growth modelling

Failures caused by the combined actions of fatigue, corrosion and wear are important safety concerns for mooring chains used on floating structures in the oil and gas industry. Prediction of remaining corrosion fatigue life based on surface condition could therefore be a useful tool for the continued safe operation of corroded chains. This paper investigates the use of crack growth modelling for estimating the remaining corrosion fatigue life of mooring chains that exhibit significant pitting corrosion damage. A crack growth modelling approach is used to produce remaining fatigue life estimates for a selection of severely pitted mooring chains. Using fatigue crack growth rate test results for grade R4 high strength mooring chain steel, empirical crack growth laws are presented for free corrosion and cathodic protection conditions at load ratio R = 0.1. Two different methods for establishing equivalent cracks from surface scans of corrosion damage are presented. The mooring chains are proof loaded as part of their manufacturing process. Residual stresses introduced during this process have therefore been determined by finite element analysis and accounted for in the fatigue crack growth predictions. One of the equivalent crack models, accounting for the single dominant corrosion pit, provided quite accurate fatigue life predictions when compared with full scale test results.

Investigation of the Pipeline Coating Properties Degradation to Increase the Energy Efficiency of the Cathodic Protection Stations

In this paper, it is proposed to investigate the influence of the parameter providing the rate of pipeline coating degradation on the protective length of cathodic protection systems (CPS). Comparison of the calculated values of the pipeline coating resistance with the predicted values is carried out according to the theoretical distribution of the pipeline coating resistance in time. The difference between the practical value of the parameter providing the rate of coating degradation of the considered pipeline section from the predicted one is determined. The dependence of the parameter providing the rate of pipeline coating degradation on the protective length of the CPS has been formed, which makes it possible to reduce the number of cathodic protection stations along the pipeline path at the design stage, and to diminish their energy consumption in the electrochemical protection system from corrosion of oil and gas pipelines.

Некоторые аспекты проблемы защиты птиц от поражения электрическим током на воздушных линиях электропередачи в Казахстане

Некоторые аспекты проблемы защиты птиц от поражения электрическим током на воздушных линиях электропередачи в Казахстане

Growth Kinetics of Calcareous Deposits on Thermally Sprayed Aluminum Coatings in Natural Seawater

The formation of calcareous deposits on thermally sprayed aluminum (TSA)-coated surfaces immersed in natural seawater and connected to a cathodic protection system is a recurring issue. There is at present limited knowledge on the calcareous deposits’ formation kinetics on TSA in natural seawater following prolonged exposure at different temperatures. In this study, bare 25Cr super-duplex stainless steel (SDSS) and TSA-coated SDSS tube coupons (with and without a silicone-based sealer) were exposed to natural seawater under potentiostatic cathodic protection (CP) and open-circuit potential (OCP) conditions at different temperatures (i.e., 20°C, 35°C, 60°C, and 80°C) for 1.5 y. The coupons were extracted at various intervals to construct growth kinetics curves under various test conditions. The deposits were subsequently examined using scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. For all of the specimens, the deposits on the exposed surfaces increased with exposure time. Fewer deposits were seen under CP conditions than OCP at low temperatures (20°C and 35°C), whereas more deposits were observed with CP than those at OCP at high temperatures (60°C and 80°C). Last, a recommended protection potential of −0.90 VSSC (VAg/AgCl) and cathodic current density values of −8 mA/m2 and −15 mA/m2 were obtained based on the findings of this study.

Complete Integrated Automation of the Electrochemical Corrosion Protection System of Pipelines Based on IoT and Big Data Analytics

This article is devoted to the issues of creating an adaptive intelligent system, for monitoring and controlling the technological process for electrochemical corrosion protection of main pipelines (MP), which has been designed for remote control of electrochemical protection (EChP) parameters and their optimization as well as adaptive control of the parameters of cathodic protection stations while taking into account changes in external conditions. The multi-objective problem of optimizing the operating modes of cathodic protection stations (CPS) is considered because optimization is carried out according to both the criterion of optimal distribution of the protective potential (uniform distribution of the protective total (pipe-to-soil) potential along the length of the pipeline) and to the criterion of the minimum total protective current of stations. The structure of the distributed electrochemical protection system is described in the article. A more complete picture of the protection of the pipeline and solving the problems of optimizing the electrochemical protection modes in real time is possible due to remote monitoring of control and measuring points (CMP) in the middle of the pipeline between neighboring cathodic protection stations, as well as in all corrosion and hazardous zones where they are also installed. In addition to the often-used GSM/GPRS networks in electrochemical protection systems, an energy-efficient LPWAN (Low-Power Wide-Area Network) data transmission network is also used and data collection is carried out using a cloud IoT platform. The functionality of the system is described, web application screens are shown in various operating modes for remote monitoring and control of the protective parameters of cathodic protection stations is reported. Analytical data processing for the tasks assessing the protection of objects in the pipeline system against corrosion are also shown. The system ensures that the electrochemical protection process is maintained at an optimal level between the destructive zones of “underprotection” and “overprotection”, taking into account monitoring data, geological conditions at the pipeline site, climatic or seasonal changes and other factors. In general, this system provides an increase in the reliability of the electrochemical protection system as a whole and, accordingly, it prevents possible emergency situations on the pipeline system while also reducing the cost of pipeline maintenance due to the reliability and continuity of protection.

Regularities of Stress-Corrosion Cracking of Pipe Steel 09G2S at Cathodic Polarization in a Model Soil Environment

Peculiarities of corrosion-mechanical fracture of 09G2S pipe steel samples in the conditions of cathodic protection were investigated. It was established that depending on the level of protective potential, stress-corrosion cracking of pipe steel of a ferrite-pearlite class 09G2S can occur by different mechanisms. The range of protective potentials was determined, at which the anodic dissolution and hydrogen embrittlement occur simultaneously during the fracture of steel, namely from -0.85 V to -1.0 V. The existence of the above mechanisms is confirmed by the change in the strength and viscosity properties of the steel and the morphology of the fractures. For steels of other manufacturing technology and grades, these potential areas may differ.

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.

FEM simulation of a grounded carbon steel pipe under impressed current cathodic protection

ABSTRACT Cathodic protection is a well-known technique to control corrosion of buried structures, even in the presence of a grounding system. In fact, without cathodic protection, the grounded carbon steel structure is subject to galvanic corrosion due to the coupling with Cu wires or rods, being the latter more noble than carbon steel. In the present study, different scenarios have been modelled by finite element method (FEM), to study the effect of coating defects, high and low protection current densities and different soil resistivity on cathodic protection condition. The simulations highlight the paramount importance of two parameters: the definition of a minimum total protection current (pipe and grounding) to ensure a proper protection level and the soil resistivity.

Effect of AC interference on the corrosion behavior of cathodically protected mild steel in an artificial soil solution. Part I: Investigation on formed corrosion product layer

AbstractAC‐induced corrosion is a big threat even for cathodically protected pipelines nowadays. While this phenomenon was intensively investigated in the last decades, the corrosion mechanisms due to AC interference remain unclear. In the present work, investigations on the surface processes on cathodically protected mild steel during AC polarization have been performed. They utilized high‐speed potential measurements that have demonstrated the influence of the polarization parameters on the resulting alternating voltage. The corrosion product layer was characterized with scanning electron microscopy, electron probe microanalysis, and Raman spectroscopy, which clearly show the effect of the parameters of the applied alternating current on the surface under different cathodic protection (CP) conditions. It was demonstrated that the properties of the formed corrosion product layer, meaning the layer thickness, amount of oxygen, and so on, is not only dependent on the AC polarization parameters but also on the CP potential itself.

Tribocorrosion Behavior of Typical Austenitic, Martensitic, and Ferritic Stainless Steels in 3.5% NaCl Solution

Tribocorrosion behaviors of typical austenitic (ASTM 316), martensitic (ASTM S41500), and ferritic (ASTM S44660) stainless steels were investigated in a 3.5% NaCl solution under cathodic protection conditions, and variations in the microstructures and chemical compositions of worn surfaces were further analyzed. The results showed that the friction coefficient and wear rate of austenitic steels were lower than those of ferritic and martensitic steels in 3.5% NaCl solution with cathodic protection. Additionally, the tribocorrosion properties of ferritic steels were obviously unaffected by load. Wear mechanisms of the three typical stainless steels mainly included abrasive wear at lower loads and plastic deformation at a higher loads. Furthermore, in austenitic steels, variations in microstructure and chemical composition confirmed that a higher load was beneficial to the transformation of austenite to martensite; thus, the hardness and wear resistance were improved. Compared with austenitic steels, the phase compositions of martensitic and ferritic steel were more stable during sliding, and the surface hardness of martensitic steel increased due to the surface phase and microstructure transformations induced by sliding. In addition, the total damage to steel was mainly caused by mechanical wear and the interaction between corrosion and wear. Therefore, ASTM S44660 and 316 were suitable for high-load corrosion-wear environments and low-load corrosion-wear environments, respectively, providing guidance for material selection under practical conditions.

Transformers polychlorinated biphenyls analysis and waste management in gas companies, case study: Iran

ABSTRACT Polychlorinated Biphenyls (PCBs) are categorised as a type of persistent organic pollutants (POPs). In developing countries, transformer oils are the major sources of PCB release to the environment. . This study examined the pollution of PCBs from transformers of gas company cathodic protection stations in Qom province, during 2011. The PCBs were measured using the electrochemical method. According to the results, the PCBs concentration of transformers oil was ranged between 0 and 958 ppm. Most stations PCBs concentrations (over 60%) were higher than recommended level (50ppm) enacted by theDepartment of Environment (DOE) of Iran. The results showed that among all cathodic protection stations; 10.4% were in a safe level, 29.2% in precaution level, and 60.4% in dangerous level. ANOVA test presented the significant difference between levels of the PCBs in different stations (P < 0.05). It is recommended that proper and safe waste management strategies for the exposure, transportation, and storage for this type of waste be taken into account.