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Statistics Analysis Measures Painting of Cooling Tower

DOI: 10.1155/2013/389159

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Abstract:

This study refers to the cooling tower of Megalopolis (construction 1975) and protection from corrosive environment. The maintenance of the cooling tower took place in 2008. The cooling tower was badly damaged from corrosion of reinforcement. The parabolic cooling towers (factory of electrical power) are a typical example of construction, which has a special aggressive environment. The protection of cooling towers is usually achieved through organic coatings. Because of the different environmental impacts on the internal and external side of the cooling tower, a different system of paint application is required. The present study refers to the damages caused by corrosion process. The corrosive environments, the application of this painting, the quality control process, the measures and statistics analysis, and the results were discussed in this study. In the process of quality control the following measurements were taken into consideration: (1) examination of the adhesion with the cross-cut test, (2) examination of the film thickness, and (3) controlling of the pull-off resistance for concrete substrates and paintings. Finally, this study refers to the correlations of measurements, analysis of failures in relation to the quality of repair, and rehabilitation of the cooling tower. Also this study made a first attempt to apply the specific corrosion inhibitors in such a large structure. 1. Introduction Generally the concrete comprises a protective environment of the reinforcement for the two reasons following.(i)The aqueous solution of the pores of the reinforcement is intensely alkaline due to lime, which is the product of reaction of the cement hardening, its pH between 12.5 and 13.9. Under these circumstances, steel is superficially covered by a passive layer of iron oxides, which impedes its corrosion. Steel corrosion is restrictive to the maintenance of this passive layer; an action is so slow that it could practically be ignored.(ii)The concrete acts as a natural barrier between the reinforcement and the various corrosive elements of the environment (such as oxygen and carbon dioxide) as well as other substances which may induce corrosion (such as chlorides). In time, cement may lose its protective capacity, for example, due to carbonation which is the reaction of carbon dioxide with calcium hydroxide. Then the pH may reach scales lower than 9, so the steel passes from the passive into the active state. Another reason for the corrosion of the reinforcement is the existence of chlorides. Chlorides penetrate the passive layer of oxides and cause

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