Corrosion Tests of Plumbing Materials at Water Works

Abstract

Corrosion tests of three types of water supply pipes (carbon steel, galvanized steel, and copper) were carried out at seven water works of major cities in Japan (Tokyo, Osaka and Nagoya). In the test, the treated water of the works was allowed to flow through pipes in a once-through testing apparatus. The results obtained are summarized as follows: 1) Water temperature alone influences the corrosion rate of carbon steel. 2) The corrosion rate of galvanized layer is proportional to the activity of H⁺(10^-pH). This trend is highly pronounced in low-pH water with high acidity (dissolved CO₂). 3) Corrosion trend of copper is similar to that of galvanized steel; corrosion rate increases with decreasing pH and increasing acidity. 4) Corrosion potential of galvanized steel shifted towards nobler values with time, while steel and copper showed relatively constant values. The reciprocal of polarization resistance showed fairly good correlation for galvanized steel with corrosion rate measured by weight loss, when iR-drop compensation was properly made.