Copper Plating on Stainless Steel Pump Impellor

In the chemical plant that I support, I have a problem with copper plating out onto a ferralium pump impeller. The stream being pumped is organic, but contains small amounts of copper and sulfuric acid. The process is 190 °C. My real problem is that this copper then flakes off of the impeller and collects on the pump seal faces causing seal leakage. Is it possible that I have set up some sort of unintentional plating process inside of the pump? And if so, what can be done about it?

Copper will "immersion plate" onto stainless, so that is probably what you are seeing. But I am surprised that it could grow thick enough to flake off because the plating ceases the moment the solution can no longer see stainless steel. Is there any possibility that these particles came from elsewhere and just look like copper particle because they too have immersion plated? Is the solution well filtered before reaching the pump?

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

First of two simultaneous responses -- 2006

I have had the particles analyzed on the seal faces and they are 100% copper. Is it possible that the turbulence in the pump is causing the pieces to come off?

No, this fluid is not filtered before reaching the pump. It comes directly off the bottom of the hold tank.

Second of two simultaneous responses --

After you follow Ted's comments, try getting a high nickel alloy impeller that is also resistant to sulfuric that is that hot.