Galvanic Corrosion

Brass-to-lead junction: Utility 2

Surface water supply; chlorine disinfection; phosphate corrosion control

Dezincification of brass at junction

Note the apparent reversal of the normal galvanic series. That is the brass, not the lead is corroding. This could be explained by the much lower potential of Zn relative to Pb, leading to lead acting as the cathode instead of the anode:

Cathode (iron)                                            ½O₂  + H₂O  + 2e^- →  2OH^-

Anode (zinc component of brass)           Zn → Zn²⁺  +  2e^-

 

 

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