Galvanic corrosion concrete structures

Rebars not entirely embedded in concrete. Macrocell corrosion can occur when there are macroscopic defects in the concrete (cracks with large width, honeycombs, delaminations, etc.) or when there are metallic parts connected to the rebars that are only partially embedded in the concrete. This case is important for structures immersed in seawater or in aggressive soil. Besides being subjected to direct attack, those parts in direct contact with water or soil may also undergo more severe attack caused by the galvanic coupling with steel embedded in concrete. 

All of the correlations seen above refer to situations of steel reinforcement in the free corrosion condition, that is, in the absence of factors that modify the potential of the system. They are in particular not appHcable to structures in concrete containing corrosion inhibitors galvanized reinforcement (on stainless steel it is possible in the same way) structures subjected to electrical fields produced by stray current that induce current exchange between reinforcement and concrete (this case is dealt with in Section 9.4). 

P. Pedeferri, Stray Current Induced Corrosion in Reinforced Concrete Structures Resistance of Rebars in Carbon, galvanized and Stainless Steels (in Italian), La Metallurgia (10 ... 

Galvanized-steel rebars can be used as a preventative measure to control corrosion in reinforced concrete structures exposed to carbonation or mild contamination with chlorides, such as chimneys, bridge substructures, tunnels and coastal buildings. 

L. Bertolini, M. Gastaldi, T. Pastore, MP. Pedeferri, P. Pedeferri, Effects of galvanic coupling between carbon steel and stainless-sted reinforcement in concrete , Int. Conf. on Corrosion and Rehabilitation of Reinforced Concrete Structures, Federal Highway Administration, Orlando, 7-11 December 1998 (CD-ROM). 

This second edition provides information on corrosion of steel in concrete in atmospherically exposed concrete structures with some additional information on early 20th century steel framed stone and brick buildings. The sections on corrosion theory, corrosion monitoring, galvanic cathodic protection and other areas have been introduced or expanded to reflect the changes of the past decade since the first edition. The increasing number of relevant national and international standards is also reflected in the text. 

Electrochemical protection is divided into cathodic and anodic protection. Cathodic protection based on the change of potential of a metal in the negative direction is realized in electrolytic environments, in most cases neutral, mainly of steel and reinforced concrete structures. A well-designed and correctly realized CP reduces the corrosion rate to almost zero. In practice it is realized with the use of an impressed current or protectors (galvanic anodes). The scope of application is enormous and continuously increases. With the use of this technology it is possible to protect vessels and ships, docks, berths, pipelines, deep wells, tanks, chemical apparatus, underground and underwater municipal and industrial infrastructure, reinforced concrete... 

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