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


-----

Lead drag problem in Pb-Zn bath

October 6, 2011

We have a Pb-Zn continuous galvanizing line. We often get the lead drag problem.
Why does the Lead drag happen?
How to reduce this problem ?
Thank you,

Syaiful Mukti
engineer - Jakarta, Indonesia

---

Hi, Syaiful.

What do you mean by "lead drag problem". Can you use a few more words to describe it? Thanks.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October , 2011

---

October 7, 2011

Sir:

I suggest to you to modernize and get rid of the lead. This lead drag out can be caused my many problems, the most likely of which are unpickled steel or bad flux or both.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA

---

October 14, 2011

Dear Mr. Syaiful,
In a Pb-Zn pot, the strip pulls the molten metal along as it moves through the molten lead. If the stabilizing and correcting rolls are turning, the rotating action removes the lead from the moving strip. In this case there will be no lead drag.
If any of the roll stops turning,the strip will continue to pull some of the lead through the molten zinc usually at the center of the strip. That portion of the strip is coated with lead instead of zinc.
To avoid such "lead drags" make sure your pot stabilizing / correcting rolls are turning.
The rolls do not turn due to several reasons. If it is a wet flux line, the roll surface may be coated with flux due to flux pull through.
Strip with very bad center buckles may also cause lead drags.
Reducing your line speed at the expense of productivity will remove lead drags.

Best regards

Vooyk

Voo Kwee
- Karachi, Pakistan