TEMPORAL CHANGES OF CORROSION LOSSES AND CORROSION RATES IN WATER PIPES

Abstract

Water distribution systems are often constructed of metal tubes, which in addition to its good properties, especially mechanical, has also tendency to corrosion. Increased activity of corrosion processes significantly affect not only the time- life of the pipe, its failure rate and reliability, but also changes hydraulic conditions of water supply system and may result in poor water quality. Price increase of the water caused a reduction of water consumption and the extension of the travel time of the water in distribution system. This also influences the interaction of the transported water and pipe material. For the reasons, stated above, we observed the corrosive effect of the water from water source Pernek on the pipe with the short- and long- term corrosion tests. Tests are based on measurements of the weight loss difference of the test sample after 30 and 60 day exposure to flowing water. Since short time (30-60 day) test does not always give an accurate picture of the interaction between water and pipe, we extend the test up to two years. During these long term test we have observed not only the corrosion losses and the corrosion speed, but also the formation of the corrosion layer and its thickness. Corrosion losses between 30 and 60 day were almost in linear course, but during longer tests corrosion losses speed decreases and the average corrosion rate for 2-year test reached only about 39% of the corrosion rate determined from short term tests.