Abstract
The first water leak was generated in the screw in the branch pipe later about three years the use beginning in galvanized steel pipe for chilled and hot water. Afterwards, the water leak happened in succession almost in branch pipes. Corrosion pits of bowl type were caused by generating the tubercles in piping in some places under that, and it caused the water leak. It is guessed the local corrosion by the electric potential reversal of the zinc and the carbon steel from the electric potential comparison with a corrosion part and peripheral health part (zinc plating layer remaining part).In this report, the state of corrosion of piping and the measurement of the electric potential are shown by the cut sample pipes, and the water analyses results are shown.
