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Corrosion
Published in Mavis Sika Okyere, Mitigation of Gas Pipeline Integrity Problems, 2020
Cathodic protection works on the basis that during corrosion of steel, electric current and difference in potential exist between the corroded area, bare steel, and the ground. A superimposed voltage and current can suppress this reaction and reduce or eliminate corrosion at points where the coating system has broken down or is insufficient.
Network operation and maintenance
Published in Nemanja Trifunović, Introduction to Urban Water Distribution, 2020
Cathodic protection - Cathodic protection is an electrical method for preventing metallic corrosion. It forces the protected metal to behave as a cathode and therefore unable to release electrons. Basic methods of applying cathodic protection are: Cathodic protectionthe use of inert electrodes (with high level of silicon cast iron or graphite) powered by an external source which forces them to act as anodes,the use of magnesium or zinc as anodes that produces a galvanic reaction with the pipe material. Being more reactive than iron, they corrode, thereby keeping the pipe protected (sacrificial corrosion). Sacrificial corrosion
Ten Years of Cathodic Protection in Concrete in Switzerland
Published in J. Mietz, B. Elsener, R. Polder, Corrosion of Reinforcement in Concrete — Monitoring, Prevention and Rehabilitation, 2020
Cathodic protection is an active protection procedure in which the electrochemical corrosion cycle is electrically influenced. The method uses the fact that the rate of corrosion is dependent on the electrochemical potential. Through the impact of an adequately high protective current from a d.c. source (usually a rectifier) the potential of the protected part of the structure is shifted in the negative direction thus reducing the rate of, or preventing, the corrosion. Inert-anodes are used to inject the protective current into the structure, the negative pole of the rectifier being connected to the protected metal and the positive pole to the anode. The literature has several detailed descriptions of how CP functions [2] and, in addition, national and international norms and guides have been set [3] or are in preparation [4].
Corrosion monitoring at the interface using sensors and advanced sensing materials: methods, challenges and opportunities
Published in Corrosion Engineering, Science and Technology, 2023
Vinooth Rajendran, Anil Prathuru, Carlos Fernandez, Nadimul Haque Faisal
Galvanic corrosion is electrochemical process that starts when two different potential metals are directly connected (creating an interface) in presence of an electrolyte, as illustrated in Figure 3b [22]. Combination of temperature and moisture levels at the interface increase the corrosion reaction. Electrons move from more active metal (anode) to more noble metal (cathode) [26]. Galvanic cell builds when two different potential metals are linked [e.g. iron (−0.440 V), copper (+0.334 V) with respect to the hydrogen reference electrode]. Potential variations between those two metals are the driving force for corrosion. Iron ions (Fe2+) travel from anode to cathode through the electrolyte. Hydrogen ions (H+) are released from the cathode. In the cathode, Fe2+ ions merge with OH− ions to form the iron hydroxide, Fe(OH)2. In galvanic corrosion, the visibility of the corrosion at the interface is very low. Specified inspection or monitoring methods are required to inspect the interface condition frequently to avoid system failure. The polymer insulation materials or protective coatings between the interfaces can avoid the direct contact of the different materials and stop the electron's transfers. Selection of the materials can help to reduce the potential difference of the materials and minimise the driving force [22,27]. In general, galvanic corrosion cell does not need any external power source. It is an advantage to make a galvanic cell underground with a soil interface between the pipeline and high potential materials to prevent the corrosion on the pipeline. This method is generally known as the sacrificial anode system in cathodic protection.
Effect of cathodic protection methods on ferrous engineering materials under corrosive wear conditions
Published in Corrosion Engineering, Science and Technology, 2020
F. Brownlie, L. Giourntas, T. Hodgkiess, I. Palmeira, O. Odutayo, A. M. Galloway, A. Pearson
One of the most common methods to suppress corrosion-related damage is cathodic protection [11]. Cathodic protection is attained by applying an electrical current, which, if properly controlled, reduces the corrosion rate of the metallic alloy to zero. The external supplied current polarises the entire surface of the material, which is being protected. Therefore, cathodic reactions become the more dominant reaction, while the anodic reactions are suppressed. It is well known that cathodic protection can mitigate both uniform and localised corrosion. There are two types of cathodic protection: impressed current cathodic protection (ICCP) and sacrificial anode cathodic protection (SACP) [12].
A new solution technique for cathodic protection systems with homogeneous region by the boundary element method
Published in European Journal of Computational Mechanics, 2018
W. J. Santos, S. L. D. C. Brasil, J. A. F. Santiago, J. C. F. Telles
Cathodic protection (CP) is an electrochemical technique used to prevent or to reduce corrosion rate of metallic structures. Electrochemical systems require anode, cathode, electric circuit and electrolyte to promote the current flux between anode and cathode. Thus, cathodic protection can be applied to buried, submerged or, less frequently, concrete structures. The protection of the structure against corrosion can be achieved by making it the cathode of an electrochemical cell. Thermodynamically, steel is immune to corrosion processes when the electrochemical potential achieves a predetermined value, as prescribed by specific standards (ISO/15589-1, 2015; NACE/SP0169, 2007).