Corrosion Damage of Water Supply Piping in Urban Buildings

Fujii Tetsuo, Kodama Toshiaki, Baba Haruo

doi:10.3323/jcorr1974.30.11_627

More than two hundred galvanized steel pipes which had been in service were collected at 31 buildings in principal cities of Japan. Waters by which the collected pipes had served were mostly soft ones, characterized by low hardness and alkalinity. Examinations of the samples included visual inspection, measurements of pit depth and corrosion potential, and analyses of corrosion products by X-ray and infrared methods. Dense and heavy tuberculation following complete loss of the zinc layer was observed on large-diameter pipes used for delivery and supply mains. On small-diameter pipes used under intermittent flow conditions, localized attack was predominant with galvanized layer on the rest of surfaces. The predominant corrosion product on galvanized layer was a mixture of amorphous zinc silicate and carbonate. In some cases well-crystallized hemimorphite (zinc silicate) was detected. The penetration rate of a maximum pit ranged from 0.12 to 0.14mm/year. In soft waters, loss of carrying capacity due to tuberculation and red water are more frequent troubles than water leakage.

Corrosion Damage of Water Supply Piping in Urban Buildings

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