Galvanized steel pipe is a very common material used in domestic water systems, primarily for larger pipe diameters (DN 50 or 80 (NPS 2 or 3) and above) due to the expense of copper pipe. While galvanized pipe is allowed in most building codes, it has corrosion issues when used for hot, softened water service. The low mineral content in soft water is desirable for reducing scale build-up, but detrimental to corrosion resistance. When there is sufficient calcium hardness in the water, the calcium reacts with the galvanizing to form a protective layer on the internal pipe surface. Without that protective layer, the pipes are significantly more susceptible to corrosion. Presented in this paper are case studies of corrosion issues in galvanized water piping in a stadium, hotel, and county government building. Details of the corrosion mechanism and mitigation strategies are also discussed.

Subject
Buildings, Zinc rich coatings, Water, Materials, Piping, Piping systems, Galvanized coatings, Internal surfaces, Surface layers, Steel, Pitting, Corrosion protection, Zinc
Keywords:
galvanized pipe, domestic water system, soft water, corrosion
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2017
Association for Materials Protection and Performance (AMPP)
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