Influence of moisture on corrosion behaviour of steel ground rods in mildly desertified soil

Skrynkovskyy

et al. 2019

EEJET

Сформовано множину визначальних параметрiв та iнформацiйних потокiв для моделювання етапiв зондування зовнiшньої поверхнi пiдземного металевого трубопроводу (ПМТ) з урахуванням водневого показника (ВП) ґрунту, який контактує з металом труби. Проведено обстеження зразкiв сталi 17Г1С, помiщених у кислi, лужнi та нейтральнi середовища. Обстеження здiйснено за допомогою вимiрювача поляризацiйного потенцiалу у комплексi з безконтактним вимiрювачем струму. Сформульовано принципи використання нейронної мережi (НМ) для опрацювання результатiв експерименту. Розроблено базу даних, яка вiдповiдає початковим умовам для контролю ВП ґрунту на межi з металом в реальних умовах. Запропоновано елементи оптимiзацiйного пiдходу щодо оцiнювання ВП ПМТ з покриттям у ґрунтовому середовищi. В основi пiдходу лежить мультиплiкативний квалiметричний критерiй якостi для дiлянки ПМТ з урахуванням двох груп коефiцiєнтiв. Перша група коефiцiєнтiв стосується внутрiшнiх коефiцiєнтiв i характеризує метал трубопроводу, а другазовнiшнього середовища (ґрунтового електролiту). Запропоновано елементи оптимiзацiйного пiдходу щодо оцiнювання ВП трубопроводу з покриттям у ґрунтовому середовищi. Представлено НМ для системи "трубопровiд-покриття", яка: 1) здатна сприяти розв'язуваннi задачi кластерного аналiзу i класифiкацiї образiв; 2) дозволяє виконувати обробку даних без попереднього спектрального перетворення, оперуючи з дискретними вiдлiками iнформацiйних сигналiв. Запропонований тип НМ дозволяє їй динамiчно розширювати власну базу знань про можливi типи дефектiв контрольованих об'єктiв (трубопроводiв) у процесi роботи. З допомогою НМ для ПМТ (зi сталi 17Г1С) проведено оцiнювання ВП ґрунту для трьох ситуацiй. Вiдзначена iнформацiя є важливою для удосконалення методiв контролю ПМТ нафтогазових пiдприємств, зокрема, методик коректного оцiнювання густини анодного струму у дефектах металу з урахуванням нелiнiйного характеру iнформативних параметрiв Ключовi слова: пiдземнi трубопроводи, нафтогазовi пiдприємства, корозiйнi струми, поляризацiйний потенцiал, водневий показник, нейронна мережа

Section: Literature Review and Problem Statementmentioning

confidence: 99%

“…The factors determining influence of corrosion activity of soils on the UMP metal show difficulty of diagnosing oil-and-gas enterprise UMPs in soil media. As is well known, the list of main factors includes [2,4,5]:…”

Section: Introductionmentioning

confidence: 99%

Improving the diagnostics of underground pipelines at oilandgas enterprises based on determining hydrogen exponent (PH) of the soil media applying neural networks

Skrynkovskyy

et al. 2019

EEJET

“…Therefore, the pipeline steels were prone to failure by pitting corrosion . Corrosion of buried metals can be affected by a variety of factors in a corrosive soil environment, including: soil water content, chemical constituents, the pH of the corrosion environment, electrical resistivity, soil type, salinity, porosity, and others, which have been investigated extensively in previous studies . However, the effect of soil particle size, especially in the sand fraction, on the electrochemical corrosion behavior of underground metal structures is not yet clearly understood.…”

Section: Introductionmentioning

confidence: 99%

The influence of particle size on the long‐term electrochemical corrosion behavior of pipeline steel in a corrosive soil environment

Hou

et al. 2017

Materials & Corrosion

In this work, the effect of particle size (0.25, 1.0, 1.5 mm) on the electrochemical corrosion behavior of X70 pipeline steel in a 1.5 wt% NaCl sandy soil corrosion system was investigated by electrochemical techniques including linear polarization resistance, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) in combination with SEM‐EDS surface analysis, and X‐ray diffraction characterization. The laboratory experiments indicated that the corrosion rate of X70 pipeline steel increased with decreasing soil particle size to less than 1.0 mm and was mainly determined by a cathodic reaction. Whereas when the soil particle size increased beyond 1.0 mm, the corrosion rate of X70 steel decreased as the soil particle size decreased and the dominant reaction was metal dissolution in the bulk zone, and the corrosion rate was determined by anodic reaction. Additionally, the results of analysis of the metal surface morphologies agreed with the electrochemical measurements results. Corrosion of X70 pipe steel is affected by particle‐sizes in a corrosive soil environment.

“…Therefore, pipeline steels were very susceptible to failure by pitting corrosion . Corrosion of buried metals can be affected by a variety of factors in soil corrosive environments, including soil water content, chemical constituents, the pH of the corrosive environment, electrical resistivity, soil type, salinity, porosity, and others, which have been investigated extensively in previous studies . However, the effect of soil particle‐size distribution (PSD), compared with continuous gradation and gap gradation especially, on the electrochemical corrosion behavior of underground metal structures is still poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Role of typical soil particle‐size distributions on the long‐term corrosion behavior of pipeline steel

Han

Hou

et al. 2016

Materials & Corrosion

The electrochemical behavior of X70 pipeline steel in a 1.5 wt% NaCl sandy soil environment with two typical particle size distributions (PSD), continuous gradation (CG), and gap gradation (GG) was investigated using electrochemical measurements, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results showed that, as the burial time increased, the corrosion rate of X70 pipeline steel increased in the initial corrosion stage, decreased at an intermediate stage, and then increased in the final stage in these two typical soil PSD environments. However, compared with the soil PSD pertaining to the CG environment, the corrosion rate of steel increased significantly in the GG environment, as evinced by the severe corrosion spots observed on the steel surface, attributed to the fact that, in the soil PSD for the GG environment, both the extent of liquid dispersion, and the number of galvanic cells increased, accelerating the cathodic step, i.e., oxygen-reduction reaction in the three-phase boundary (TPB) zone, and anodic step, i.e., the metal dissolution stage, of the X70 pipeline steel corrosion process, respectively. Both the anodic and cathodic processes were activation controlled. Thus, the corrosion of X70 pipeline steel was considerably dependent on the soil PSD in sandy soil environments. Materials and Corrosion 2016, 67, No. 5 Role of soil PSD on the corrosion behavior of steel Figure 15. SEM micrographs of the surface morphologies of X70 pipeline steel in (a) CG PSD soil; (b) GG PSD soil www.matcorr.com