The internal corrosion of cast iron and steel pipes is one of the main issues that drinking water distribution operators are facing. This study evaluated the relevance of 10 known corrosion indices according to their estimate of corrosion rate and iron particle release for 20 different water qualities. Pilot-scale contact trials were run over 45 days using cast iron and steel coupons. Corrosion rate was measured by coupon weight-loss and by an online linear polarization rate probe. Particle release was monitored by an online turbidimeter. The results showed that none of the indices properly predicted the level of risk associated with each water and that corrosion and particle release were not correlated. Two novel indices were developed to predict the corrosion and particle release risks independently of each other. The corrosion index showed a strong linear correlation with the corrosion rate of cast iron and slightly less reliable results for steel. The Particle Emission Index presented good correlation with turbidity in waters following contact with cast iron. These two indices thus showed interesting potential as tools to limit internal corrosion risks for metal pipes in water distribution networks.

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