Dezincification of bronze impellers
Dezincification of bronze impellers
(OP)
Has anyone experienced dezincification of pump impellers? We started our water treatment plant 5 years ago and now have to replace all our impellers on are vertical turbine pumps. The original material was a brass alloy 875 ( 15% Zinc ) and the manufacturer is recommending a Tin Alloy 903. We are also trying to find out why this occurred. Are water at the time of startup would have been ph 6.8 and have a chlorine residual of 1.0 mg/l free. The water is low in alkalinity ( 10 mg/l ) It appears that the damage was done in the first two years as the flows had dropped off by 12% during this time. We started using a zinc polyphosphate for corrosion control after the 2 years and pump production stayed the same as if the damage stopped occurring. Any comments would be appreciated.





RE: Dezincification of bronze impellers
Oxygen and carbon dioxide in water.
Stagnant or slow moving waters.
Slightly acidic water, low in salt content and at ambient.
Low conductivity, minerals, + oxygen.
Waters with high chloride ion.
Neutral or alkaline waters, high in salt content and at or above room temperature.
RE: Dezincification of bronze impellers
My guess is that the damage stopped because the stress on the now damaged impellers was low. The outer tips of the vanes go very fast.
Corrosion never sleeps, but it can be slowed down.