Where the
world gathers for metal finishing
Q&As since 1989




-----

Dross & lead on galvanizing kettle floor

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