Summary for dross and lead on kettle floor Discussion
Dross & lead on the kettle floor are described as separate layers, not mixed together. In the first response, Dr. Thomas H. Cook explains that if lead has been added to the galvanizing kettle, it melts and sinks to the very bottom, with dross sitting on top of the molten lead and molten zinc above that. He also notes that if no lead has been added, there should be no molten lead at the bottom, and warns that simply stopping lead use in hot dip galvanizing can cause very bad results unless the process is adjusted correctly. A second response adds that lead is about twice as dense as dross, so it sits below the dross when free lead is present. It also says zinc may hold about 1% Pb in solution, so at 1-1.5% Pb there is likely free lead beneath floating dross.
Q. Please
What’s the behavior of dross & lead on the kettle floor? They are mixed or they are separated as a layer? and… What is the one in the bottom?
Thank you
Dario Dobreb
– Sao Paulo, SP, Brazil
December 28, 2011
First of two simultaneous responses — December 29, 2011
Sir:
If you have added lead to your kettle it will have melted and sink to the very bottom of the kettle. The dross will be on top of the molten lead. Above the dross is molten zinc.
If you have NOT added lead to the kettle there will not be any molten lead in the very bottom of the kettle. In the USA there is movement to eliminate lead in hot dip galvanizing. There are several things you must know to eliminate lead from zinc in hot dip galvanizing. Failure to know what to do will give very bad results if you simply stop using lead.
Regards,
Dr. Thomas H. Cook
Galvanizing Consultant – Hot Springs, South Dakota, USA
Second of two simultaneous responses — January 1, 2012
Lead is about twice as dense as dross, so it sits on the bottom of the kettle below the dross. That is provided there is some in there, and not all in solution.
Zinc seems to be saturated at something not so far above 1% Pb, so if you have 1-1.5%Pb in the zinc, there’s likely to be some free lead in the bottom, with dross “floating” on top of it.
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
