OBSERVATIONS OF CORROSION OF ELECTRICRESISTANCE WELDED GALVANIZED STEEL PIPE INDOMESTIC POTABLE WATER

摘要

Information from inspection and analysis of electric resistance weldedrngalvanized steel pipe after service in residential water systems has resulted in arncompilation of observations concerning the development and severity of corrosionrnleading to failure. The observations gathered over a fourteen-year period explainrnthe development of corrosion that does not always correlate with the many factorsrngenerally thought to be responsible. The inability of the zinc coating to meet itsrntheoretical role of galvanic protection was clearly evident, and this allowedrndevelopment of localized attack and tuberculation. Both forms of corrosion resultrnfrom under-deposit corrosion, or the presence of copper ions in the water.rnTubercles that covered the weld seam resulted in severe grooving corrosion andrnaccelerated failure regardless of the weld or coating quality. It appears that therncorrosion of the plumbing system in each residence is progressive, the most severernattack taking place at the inlet end of the system and diminishing to light or norncorrosion at the downstream outlets. Pitting and grooving corrosion found in therndownstream plumbing were attributed to the techniques and components used tornplumb the system.