Abstract:
The fundamental physical and chemical data of periphery soil buried gas pipeline in Changzhou City has been carried out by the method of factor analysis,and the 9 detected variables have been summed up to common 4 factors.The result shows that the degree that every property of soil corrodes soil is different;during the period of evaluation,the factor of saltiness,moisture content,natural corrosion electric potential,oxide deoxidation electric potential and soil resistance should be chosen as main factors,but pH value and stray current generally as the main factors will not be considered.Keywords:
Soil resistivity
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Corrosion of metals in soil be able to change from comparatively fast material loss to insignificant effects, depending on soil environment. Corrosion is a process of deterioration of metal surfaces degraded into another compound. Soil is one of the medium known to have constituted to corrosion of metals. The soil creates an environment for the corrosion to react. The buried pipelines are exposed to the soil that may experience corrosion attack. The study of the soil as corrosion environment is important to mitigate the problem due to the environment and economy. There are factors that contribute to the corrosion process. This study concentrates on corrosion properties that expose to soil environment particularly underground pipelines. The mild steel coupons taken from actual pipelines, stimulating and analyzing the physic-chemical characteristics of the soil environment. The soil is sandy clay in natural. A total summed index of 2 numerical scale, thus, indicates that the soil tested was mildly to non-corrosive. The corrosion rate increase with increasing of moisture content and pH value. The observations on the coupon surface also did in order to study the morphology.
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Carbon steel is commonly used in the gas and liquid pipeline transportation due to its low price while it possesses machanical properties accepted in most industrial applications. However, it has been reported to be susceptible to corrosion when exposed to various soil conditions. Cathodic protection (CP) is the most promising and already implemented technique for protecting buried carbon steel from corrosion. This study aims at reviewing the soil properties influencing the carbon steel corrosion process in the presence and absence of CP thus also giving the effectiveness of CP. The literature review carried out in this work has identified voltammetry as the only method for monitoring and estimating carbon steel residual corrosion rate under various soil conditions. The voltammetry was found to be a very reliable method that can be used to evaluate the CP effectiveness under soil conditions. However, more experimental tests have been proposed to extend the knowledge on all soil processes taking place during carbon steel corrosion in the presence of CP. Among other soil processes referred to for future studies are the soluble ionic species behavior in the soil which is linked to steel/soil vicinity pH, long-term exposure experiments as well as CP potential (insufficient, sufficient and overprotection potential).
Carbon steel
Carbon fibers
Soil carbon
Soil test
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Deterioration of buried metal due to corrosive soil environment is a major issue worldwide. Although failure of buried metal due to corrosive soil is an old problem, yet such failures are still uncontrollable even with the application of advanced corrosion protection technologies. Therefore, understanding environmental parameters causing corrosion of buried metals are necessary. This research work reviews environmental parameters causing corrosion of buried metal in soils. These functional parameters include: moisture content, temperature, pH, soil resistivity, conductivity and microbial activity. It was found that corrosion rate of metals increases with increase in moisture content and at high concentrated acidic in pH and variation in electrical conductivity influences various metal sample in terms of effect on metal corrosion. The effect of Clay soil, Sandy soil and Loamy soil characteristics in terms of physiochemical parameters was examine and determine as a contributing factors to metal corrosion on Carbon Steel, Mild Steel and Stainless Steel. It was observed that the rate of corrosion of carbon steel is high in loamy soil followed by clay soil and Sandy soil. Also, the rate of corrosion of Stainless Steel and Mild Steel was high in Clay soil followed by Loamy soil and Sandy soil. The order of variation of the corrosion rate on the various metals can be attributed to the physiochemical properties of the soil samples. In order to demonstrate the effect of environmental parameters on metal corrosion in soil, Galerkin’s principle of finite element method was used. Furthermore, simulations were carried out with the aid of MATLAB R2007b.to monitor and predict the rate of corrosion of metals buried in soil environment. Key words: Effect, environmental, parameters, metals, corrosion, soil, finite element method
Carbon steel
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X70 steel is applied to the construction of gas pipeline massively as a new pipeline steel.Soil corrosion of X70 steel is investigated in this paper.The corrosion behavior of X70 steel in coastal soil with 38%~100% water holding capacity(WHC)is studied by polarization curve measurement and electrochemical impedance spectroscopy.The effect of WHC of soil corrosion is analyzed in detailed.The results of experiments show that X70 steel corrosion in soil of different humidities can be controlled by cathodic polarization.The compaction degree of soil and the soluble salt ionization degree lead to soil corrosion with different content of water.A high humidity has a significant effect on soil corrosion.When the WHC is less than or equal to 45%,the corrosion rate is low and changes slightly.But when it is higher than 45%,firstly the corrosion rate increases sharply,then reduces and reaches the maximum point when the water content is 65%.In a high humidity,there are middle corrosion products membrane formed on anticathodic surfaces.
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Carbon steel
Carbon fibers
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Characterization of External Induced corrosion degradation of Ajaokuta- Abuja gas pipeline system was successfully carried out. The objective of this work is to analyze the mechanism of corrosion, analyze the effect of the corrosion on oil and gas pipeline and to evaluate the corrosion potential of a pipeline route. These were achieved by carrying out resistivity experiment on every one kilometer on the right of way (ROW) of the pipeline. Soil and water aggressiveness test was also carried out on soil and water sample of the pipeline route respectively. The resistivity result was considerably high, chemical analysis revealed that the soil and water acidity is between the pH of 6.7 and 8.2 respectively, which is moderately alkaline in nature, which makes the soil environment not conducive for pipelines due to potential for corrosion attack. The chloride content of the soil and water were also high. Based on the experimental results, it was proposed that the pipe should be laid on 2-5m below the ground and that the galvanic anode for cathodic protection be located 1m below the ground, in order to avoid corrosion. It is therefore necessary to note that characterization of external corrosion is quite different from internal pipeline corrosion characterization.
Soil resistivity
Degradation
Characterization
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Soil corrosion is one of the important factors for safe operation of buried X70 pipelines.The main environmental factors of soil corrosion for X70 and Q235 steels were determined using fuzzy clustering,and the order and weight of the main factors were investigated by means of grey relationship analysis and analytical hierarchy process methods.The calculation results showed that the weihgt of factors for the soil corrosion of X70 steel decreased in the following order: pH value(0.4050),water content(0.2517),conductivity(0.1493),salt content(0.0868),Cl-(0.0501),NO-3(0.0291),SO2-4(0.0173),HCO-3(0.0107),and the results for Q235 steel were little different from those.These results provided some new reference data for establishing an evaluation method for soil corrosion of underground pipelines.
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The corrosion rates of X52 pipeline materials are measured in 25 designed types of soil in light of the content of water and the concentration of cathodic ions Cl-,SO42-,HCO3-and CO32 in the soil,based on an improved resistance method.The effect of the components of soil on the corrosive rates of X52 pipeline material is analyzed in detail.The results show that the content of water is a main factor that influences the corrosive rates of X52 pipeline materials and the cathodic ions SO42-,CO32-,HCO3-and Cl-affect the corrosive rates less.The corrosive rates increase steadily when the content of water is below 14% and decrease suddenly when it is above 14%.
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A set of studies was conducted to determine the main factors influencing the corrosion destruction of metal in underground pipelines in two studied sections of the Pasichna-Tysmenitsa gaspipeline, covering definitions of active acidity, mass fraction of moisture, the presence of sulfate ions, and metal weight loss determined by the gravimetric method. It has been established that the pipeline in the studied sections of the route is laid in a soil of uniform acidity, which is low in pH acidic, which indicates corrosiveness of the soil in relation to steel. High soil moisture from the bottom of the pipeline in two sections of the route 18.21and 19.73 %, respectively, contributed to increased corrosion damage of the metal. Corrosion of the studied soils was carried out on the basis of certain metal weight loss. It was established that the soils on the studied sections of the route, the distance between which was about 1000 m, relate to soils with a high and normal degree of corrosivity. High corrosion activity is characteristic of the soil along the lower generatrix of the pipeline, which leads to an increase in the corrosion rate of the metal of underground pipelines in this zone. The intensification of corrosion processes in the soil adjacent to the pipeline, with an increase in metal exposure time in soil, has been established. The presence of sulfate ions in soil water extracts leads to the development of biocorrosion with the participation of sulfate-reducing bacteria, which indicated the formation of biogenic hydrogensulfide.
Gravimetric analysis
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