Applicability of corrosion inhibitor was evaluated using pilot scale water distribution pipe simulator. Calcium hydroxide was used as corrosion inhibitor and the corrosion indices of the water were investigated. Corrosion indices, Langelier saturation index (LI) increased by 0.8 and calcium carbonate precipitation potential (CCPP) increased by 9.8 mg/L. This indicated that corrosivity of water decreased by corrosion inhibitor and the effects lasted for 18 days. Optimum calcium hydroxide dose was found to be 3~5 mg/L for corrosion inhibition. We suggest that monitoring of CCPP as well as LI need to be conducted to control corrosivity of water.

The purpose of this study was to evaluate the effects of Ca(OH)2 and CO2 additions on the corrosion of metal coupons (ductile iron, galvanized steel, copper and stainless steel). Corrosion rate and released metal ion concentration of ductile iron and galvanized steel was decreased by adjusting alkalinity, calcium hardness and pH with Ca(OH)2 & CO2 additions named CCPP (Calcium Carbonate Precipitation Potential) index control process. But the effects of Ca(OH)2 & CO2 additions on copper and stainless steel were less than those on ductile iron and galvanized steel. When ductile iron coupon was exposed to water treated with Ca(OH)2 & CO2 additions, the main components of corrosion product formed on its surface were CaCO3 and Fe2O3 or Fe3O4, which often reduce the corrosion rate by prohibiting oxygen transport to the metal surface.