AWWA JAW11039

Copper, a noble metal that occurs naturally in its elemental form, is almost totally impervious to corrosion from soils found worldwide. However, copper pipe or tubing is subject to external corrosion in certain situations. The basic prerequisite for corrosion is the presence of appreciable amounts of moisture. Other factors that can facilitate the corrosion process include soils having: elevated concentrations of sulfate, chloride, ammonia compounds, or sulfide; poor aeration, which supports anaerobic bacteria activity; large amounts of organic or inorganic acid; and large oxygen, neutral-salt (especially chloride), or hydrogen-ion differentials. Copper is also subject to stray direct current (DC) corrosion. Underground copper is reportedly susceptible to thermogalvanic effects and dissimilar metal corrosion. Copper water pipes can occasionally experience corrosion fatigue. Identifying the corrosion problems without excavation and mitigating the underground corrosion are also discussed. Includes 20 references, figures.