When extending a black steel pipe with copper pipe, what potential issue may arise at the junction?

When extending a black steel pipe with copper pipe, a significant concern is the potential for galvanic corrosion, which occurs when two dissimilar metals are electrically connected in the presence of an electrolyte. In this scenario, the junction of the black steel (which is iron-based) and copper creates a galvanic couple.

The black steel pipe is more susceptible to corrosion because, in such a couple, the more noble metal (copper) tends to remain relatively unharmed, while the less noble metal (black steel) can corrode at an accelerated rate. This means that the black steel pipe may start to rust at the junction with the copper pipe, compromising the integrity of the piping system over time.

Therefore, it’s crucial to address this issue by using appropriate fittings that can isolate the two metals or by applying protective coatings to prevent direct contact, thus mitigating the risk of galvanic corrosion. This understanding is vital for ensuring the longevity and reliability of the plumbing system.