PERFORMANCE OF CATHODIC PROTECTION FOR PIPE LINES

The corrosion of metallic structures buried in soils or in contact with soils has long been a serious engineering and economic problem. All over the world millions of kilometers of gas, water, oil pipelines, communication cables, power cables as well as storage tanks, buildings foundations, and many other structures are buried in the soil, suffering from soil corrosion problems which affect mainly the external surfaces of these structures. In many countries pipelines are by far the most important means of hydrocarbon transportation. This applies to the transport of crude, finished products and natural gas.It is an international problem with more structures and materials buried in the soil. The truly international scope of interest of this subject can be seen by the amount of literature and researches in this field. Attempts have been made to overcome this problem by the use of various types of techniques. The most common and applicable technique is cathodic protection.In this research a carbon steel pipe of length 100 cm buried in a wooden box submerged by soil and impressed current cathodic protection system (ICCP).was applied using power supply and electrical closed circuit, several important factors affecting the pipe protection from corrosion has been studied, like Anode position (distance and depth), soil resistivity (wet and dry), condition the pipe (coated and un-coated), distribution of potential and currents along the
pipe(cathode) and the amount of current required to achieve cathodic protection.A correlation was achieved to simulate the ranges of parameters and factors affecting Impressed Current Cathodic Protection. Regression of this model to data and results yielded parameter values vary depending on the effect of the same factor.Two equations were achieved in bare and coated pipe that explain the effect of many factors on the cathodic protection potential (-850mV) and the relation of each factors with others as shown below:
1.  Bare carbon steel pipe.