Economics buried pipelines, cathodic protection

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. 

Further chapters cover in detail the characteristics and applications of galvanic anodes and of cathodic protection rectifiers, including specialized instruments for stray current protection and impressed current anodes. The fields of application discussed are buried pipelines storage tanks tank farms telephone, power and gas-pressurized cables ships harbor installations and the internal protection of water tanks and industrial plants. A separate chapter deals with the problems of high-tension effects on pipelines and cables. A study of costs and economic factors concludes the discussion. The appendix contains those tables and mathematical derivations which appeared appropriate for practical purposes and for rounding off the subject. 

Cathodic Protection. In general, buried pipelines and tanks are protected by a combination of cathodic protection and an organic coating. This combination protects steel against corrosion in all soils, both effectively and economically, for as many years as cathodic protection is adequately maintained. 

For buried pipelines, the cost of cathodic protection is far less than for any other means offering equal assurance of protection. The guarantee that no leaks will develop on the soil side of a cathodically protected buried pipeline makes it economically feasible, for example, to transport oil and high-pressure natural gas across entire continents. 

The most frequently used materials for buried metal structures are the carbon steels. For prevention of their corrosion the most recommended, economical, and effective method is cathodic protection (CP). The use of CP is now standard procedm-e for long-term corrosion protection of imderground pipelines, oil and gasoline tanks, and other structures. With a shift of the metal potential to more of a negative value of -0.85 V versus a C11/CUSO4 reference electrode, it is possible to make the metal surface a cathode, which ensures an immune (no corrosion) state of the carbon steel. Cathodic polarization is achieved by direct current, which can be supplied either by sacrificial anodes in galvanic contact with the steel structure, or by impressed current from a rectifier. 

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