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Want to know reasons for PIT MARKS on galvanized sheet
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November 13, 2021
Dear sir ,
I'm working at 25 TPH Galvanizing unit running with 0.6 to 0.12 mm Thickness sheets. My query about pit marks defects are not really solved satisfyingly. So can you please give me a short but actual reason about how this defect evolves over the GP after coming out from the zinc bath?
- Dalli Rajhara
A. Better provide a photo of pit marks for analysis.
Mike WangIntegrated supplier of Galvanizing - Shanghai
February 12, 2022
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Ed. note: Photos should be attached to e-mail to mooney@finishing.com for posting here.
⇩ Closely related postings, oldest first ⇩
Q. Dear sir, I'm working in continuous galvanizing line having capacity of 26TPH, producing sheet of thickness 0.12 to 0.6 mm. Sometimes pit marks are observed in galvanized sheet. What is the reason for pit marks?
Harsh postiwalaEssar - Hazira, Gujarat, India
2006
A. Pit marks can be formed in many ways . If your CRFH Material is good being paid off at your entry section then many of the causes can be eliminated. The number one reason for pitting in my experience is the of a build up of iron fines on the pot turn roll " sink roll " . Having a scrapper for this roll helps greatly. Other then that replacing the roll is the only other option. Masking the problem may be done by lowering the tension setpoint at the bath. Keeping a consistent bath temp is key to not allowing buildup to occur. Also skin passing your material may help but not eliminate the problem you're having .
Mark Postema- Rancho Cucamonga, California, USA
2006
Q. Hi sir. Sandip, working in steel in India in super galvanizing line. Capacity of line is 0.3 mm to 3 mm thickness and width capacity is 750 mm to 1550 mm.
I want to know about pitting defect on the sheet surface.
Please provide me full theory about this matter. Once again I ask you.
Thank you
- khopoli, Maharashtra,India
September 16, 2014
"Hot Dip Galvanizing of Steel Structures"
by Kuklik & Kudlacek
on
AbeBooks
or
Amazon
or
eBay
(affil links)
A. Hi Sandip. "Full theory" about the defects would require a book .
rather than a forum response, but if you can explain your current situation, and/or try to phrase your question in terms of the excellent response offered by Mark Postema, the readers can hopefully help you move forward towards less pitting. Good luck!
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2014
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