Langzeitverhalten feuerverzinkter Stahlrohre in Trinkwasser unterschiedlichen pH-Wertes und unterschiedlicher Strömungsgeschwindigkeit

Long term performance of galvanized steel tubes in drinking water with different pH-value and flow velocity A 10 years' test program on galvanized steel tubes exposed to Berlin drinking water produced evidence that an undisturbed operation can only be guaranteed as long as the inner surface of the tubes is coated by metallic zinc. The zinc loss with time strongly depends on the pH-value and can be expressed by the mathematical equation . Due to the typical shape of the logarithmical function and its dependence on the pH-value a small increase of pH-value leads to an over-proportional increase in life-time of the zinc coating. pH = 7 leads to a total zinc loss within two years, whereas in the case of pH = 8 a zinc coating of 25–40 μm is still present after 10 year's time.