Survival of the Fittest: Galvanic Corrosion | Home Inspections Seattle Bellevue Everett
The image below is of the junction of copper and galvanized steel domestic water pipes in a home near Seattle.
It is common in older homes to find the replacement of galvanized pipes with copper pipes. Typically, all of the galvanized pipes are not removed due to lack of access to the pipes or excessive cost.
In this example, galvanized pipes were embedded in a concrete slab. New copper pipes were installed at all other visible areas in the house. As copper and galvanized steel are dissimilar metals, galvanic corrosion is occurring.
"Galvanic corrosion is the disintegration of metals in the presence of an electrolyte. It can occur in homes wherever dissimilar, joined metals become moist" source: NACHI
The proper connection for disimilar metal pipes is with a dielectric connection. This connection essentially creates a break in the "electrical connection" between the two disimilar metal pipes. See image below
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