Acceleration of galvanic lead solder corrosion due to phosphate

Although orthophosphate is often effective in reducing lead corrosion, bench-scale tests revealed cases in which even high doses of orthophosphate (1–3 mg/L P) in potable water increased lead and tin release from simulated soldered copper joints. Phosphate increased the galvanic current between tin and copper plumbing materials, especially in water with less than 10 mg/L SO42- and when the percentage of the anodic current carried by SO42- ion was less than 30%. Tin release was increased more than lead release from 50:50 Pb–Sn solder in these circumstances.

Research highlights
► Tests revealed higher lead and tin galvanic corrosion due to addition of phosphate.
► Tin was more strongly affected than lead by phosphate-accelerated corrosion.