Influence of organic matter on orthophosphate corrosion inhibition for copper pipe in soft water

The adverse effects of organic matter on orthophosphate corrosion inhibition for copper pipe in simulated soft water were investigated. Sodium alginate and fulvic acid were selected to simulate extracellular polymeric substance produced by bacteria and natural organic matter in potable water. The results showed that the doses of organic matters, pH values and stagnation times had significantly affected on the function of orthophosphate corrosion inhibition for copper pipe in soft water. More soluble copper release was observed in low levels for sodium alginate (1 mg/l as TOC) and in high concentration for fulvic acid (16 mg/l as TOC). When the concentration of fulvic acid was high, the 2-week aged copper pipe released more soluble copper than the 6 and 12-month aged copper pipe. The soluble copper release increased with the reduction of initial pH value. Effect of stagnation time on soluble copper release from different aged copper pipe in soft water was highly variable. Compared to the system of no organic matters, organic matters markedly decreased the efficiency of orthophosphate corrosion inhibition for copper pipe in soft water.