Galvanic series in tap water
| Metal | Potential mv (Ag/AgCl) | ||
| Nickel | 127 | ||
| Stainless 316 | 120 | ||
| Titanium | 107 | ||
| Bronze | 73 | ||
| Copper (C11000) | 73 | ||
| Brass (C28000) | -67 | ||
| Tin | -160 | ||
| Lead | -347 | ||
| Carbon Steel (A283) | -580 | ||
| Cast iron (A48) | -613 | ||
| Ductile cast iron (A536) | -647 | ||
| Zinc | -927 | ||
| Source: Matsukawa, Y. H. Chuta, M. Miyashita, M. Yoshikawa, Y. Miyata, and S. Asakura, 2011, Galvanic Series of Metals Conventionally Used in Tap Water With and Without Flow and Its Comparison to That in Seawater: Corrosion, v. 67 | |||
A metal higher on the list will tend to corrode one lower on the list if the potential difference is more than about 50 mv. Thus brass coupled to cast iron should set up a galvanic current:
Anode (iron) Fe → Fe2+ + 2e-
Cathode (brass) ½O2 + H2O + 2e- → 2OH-
where the electron is transferred through the metal and the other constituents migrate in the water. Note that brass coupled to galvanized iron should be especially prone to corrosion.