Influence of disinfection chemicals on corrosion of various metals for drinking water supply systems

摘要

Drinking water supply systems mostly consist of pipes and accessories (valves, Tspecies, etc.) made from different type of metals: galvanized carbon steel, stainlesssteel and copper and its alloys. Lifetime of installations for drinking water should bedesigned for at least 50 years, but in many cases they fail much earlier - usually dueto corrosion. The main reason for corrosion of drinking water supply systems is thecorrosivity of water as well as an increase in corrosion due to chemical and physicalmethods of disinfection of water systems due to infections caused by microorganismshazardous to health. In Europe and the world, there are knownstandardised tests for determination of impact of the disinfectants on sustainability ofmaterials used for drinking water systems. However, the duration of such tests is verylong and the price high.The main aim of our research was to characterize corrosion behavior of commonlyused metal materials in Slovenia (galvanized steel, stainless steel and copper and itsalloys) in local water with additions of disinfectants (concentration for continuousdisinfection and increased concentration used for chemical shocks). In addition, testswere performed at room and at elevated temperature. The methods used forcorrosion characterization of chosen metal materials in the contact with drinkingwater were electrochemical methods (potentiodynamic polarization and polarisationresistance) and exposures in selected environment and condition for particular time(the condition of exposed surface was examined by scanning electron microscopeand Raman spectroscopic methods after 7 and 40 days of exposure).The results of tests have shown increased corrosion activity at elevatedtemperatures. Also, different disinfectants have different influence (aggressiveness)to different types of metals. It was observed that the results of electrochemical testsare in accordance to observations obtained by visual examination of surfaces afterexposures.