Corrosion steel pipeline

Many thousands of miles of steel pipeline have been laid under, or in contact with, the ground for the long-distance transport of oil, natural gas, etc. Obviously corrosion is a problem if the ground is at all damp, as it usually will be, and if the depth of soil is not so great that oxygen is effectively excluded. Then the oxygen reduction reaction... 

Buried steel pipelines for the transport of gases (at pressures >4 bars) and of crude oil, brine and chemical products must be cathodically protected against corrosion according to technical regulations [1-4], The cathodic protection process is also used to improve the operational safety and economics of gas distribution networks and in long-distance steel pipelines for water and heat distribution. Special measures are necessary in the region of insulated connections in pipelines that transport electrolytically conducting media. 

A similar danger of corrosion lies in cell formation in steel-concrete foundations (see Section 4.3). Such steel-concrete cells are today the most frequent cause of the increasing amount of premature damage at defects in the coating of new steel pipelines. The incidence of this type of cell formation is increased by the connection of potential-equalizing conductors in internal gas pipelines and domestic water pipelines [25], as well as by the increased use of reinforcing steel in concrete foundations for grounding electrical installations [26]. 

Cooling water pipes are essential for the operation of power stations and must not cease to function. Pipelines for fire fighting are also important for safety reasons. Such steel pipelines are usually well coated. At areas of unavoidable damage to the pipe coating, there is an increased danger due to cell formation between steel and concrete where local corrosion rates of >1 mm a are to be expected [4], Damage to pipelines for fire fighting has frequently been observed after only a few years in service. 

According to Ref. 6, 70 incidents of corrosion damage for 1000 km of buried steel pipeline transporting gas were reported on average each year in Germany. For 1000 km of pipeline on lines operating at pressures up to 4 bar, 100 incidents of... 

Although iron pipes suffer from the same corrosion risk as steel pipelines, associated with the generation of a galvanic cell with a small anode and a large cathode, the risk is mitigated for iron pipelines because the electrical continuity is broken at every pipe joint. For this reason long-line currents are uncommon in iron lines and cathodic protection is rarely necessary. It also accounts for the ability to protect iron lines by the application of nonadherent polyethylene sleeving . 

Recommended Practice Control of Corrosion on Offshore Steel Pipelines, RP-0675-88, NACE, Houston (1988)... 

Technical Committee Reports of the National Association of Corrosion Engineers, USA, on pipeline corrosion control, including Statement on Minimum Requirements for Protection of Buried Pipelines , Some Observations on Cathodic Protection Criteria , Criteria for Adequate Cathodic Protection of Coated Buried Submerged Steel Pipelines and Similar Steel , Methods of Measuring Leakage Conductance of Coatings on Buried or Submerged Pipelines , Recommended Practice for Cathodic Protection of Aluminium Pipe Buried in Soil or Immersed in Water ... 

Buried steel pipeline can be protected against corrosion by cathodic protection. In this process, the steel pipe is connected to a more active metal, such as magnesium, that would corrode instead of the steel. Use the diagram to answer the following questions. 

Interpreting Scientific Illustrations A process called cathodic protection is sometimes used to protect a buried steel pipeline from corrosion. In this process, the pipeline is connected to a more active metal such as magnesium, which is corroded preferentially before the iron. The diagram below illustrates how the two metals are connected and shows the reactions that take place. 

Elements were identified within the various sectors that represented corrosion expenditures such as coatings for pipelines. The coefficient of coatings for the steel pipelines was modified so that, for instance, pipelines spend nothing on coatings, where the purpose of coatings is to prevent corrosion. After the coefficients in the steel pipeline column are modified, the column is normalized to add to one. This new matrix represents the world without corrosion. With the new matrix, the level of resources used to produce GNP in a world of corrosion would result in higher GNP than in a world without corrosion. 

Costs incurred for coatings of buried steel pipelines are corrosion costs while painting of automobiles are ascribed partly to corrosion and partly to aesthetics. In this case, one half of the cost of painting of automobiles is ascribed to corrosion. Similar judgments were made in other areas where multipurpose operations were encountered. 

J.N. Murray, P.G. Moran, Influence of moismre on corrosion of pipeline steel in soik using in situ impedance spectroscopy. Corrosion 45 (1989) 34- 3. 

F igure 8.10 Stray current originating from a cathodic protection system may cause localized corrosion on steel pipelines. (Adapted from reference [8.14].)... 

These bacteria have been quoted to have caused corrosion in systans snch as snbsea carbon steel pipelines, natural gas pipelines, and injection systems using produced brine to displace oil from the reservoir they are also a potential problem in closed water systems that conld form anaerobic environments. ... 

The most significant marine use of resins is actually in the form of paint corrosion protection systems for hulls. These include polyurethane and epoxide systems, the latter giving good alkali and solvent resistance in addition to providing superior adhesion to most substrates. Such systems take the form of zinc-rich epoxy and epoxy coal-tar combination hull paints. Epoxy powder coatings are also commonly used for the protection of steel pipelines, both on land and offshore. 

Water entering a steel pipeline at the rate of 40 liters/min contains 5.50 mL O2 per liter (25 °C, latm). Water leaving the pipe contains 0.15mL O2 per liter. Assuming that all corrosion is concentrated at a heated section 30 m in area forming Fe203, what is the corrosion rate in gmd ... 

Stray electric currents are those that follow paths other than the intended circuit, or they may be any extraneous currents in the earth. If currents of this kind enter a metal structure, they cause corrosion at areas where the currents leave to enter the soil or water. Usually, natural earth currents are not important from a corrosion standpoint, either because their magnitude is small or because their duration is short. Under some conditions, pipelines can incur considerable corrosion damage as a result of telluric currents—that is, currents induced in the steel pipeline by changes in the geomagnetic field of the earth [1]. 

Zinc is used as a coating for galvanized steel, where it helps prevent corrosion. Explain why zinc would also make an acceptable sacrificial anode for a steel pipeline. Are these two uses related in terms of the science that gives rise to their utility ... 

Underground steel pipelines must be protected from external as well as internal corrosion. Protective measures include wrapping the pipe with an impervious material, painting or covering it with a protective layer, and providing cathodic protection. 

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