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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing 1989-2024
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Galvanizing problem: Excessive aluminum in zinc
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Q. I am a galvanizer in China. Recently, we experience a lot of bare spots after hot dip galvanizing. We have suspected the aluminum content in the zinc bath is too high, about 0.5%. Please advise how can 'remove ' the excessive aluminum in the zinc.
Tan Kok Teonggalvanizing company - China
2005
A. For general galvanizing (using zinc ammonium chloride flux solution) the MAXIMUM usable aluminum in the zinc is 0.007%. There are a variety of ways to quickly and easily reduce the aluminum in the zinc. Which of these ways depends on the type of operation. That is: if this is general galvanizing, continuous sheet or whatever. Simply put, more information about your operation is needed to choose the proper method of aluminum reduction or removal.
Regards,
Galvanizing Consultant - Hot Springs, South Dakota, USA
Q. this is structural galvanizing plant.
s.k.rakshitmanager - Indian
August 12, 2024
Ed. note: Dr. Cook has been away from the site a long time, but you can review the other postings below while you await an expert to spend the time to offer you a personalized response. But minimal posting effort minimizes that likelihood.
Q. We have too much aluminum in our Zinc bath about .163 this was added as pure aluminum we have already taken out one third of the zinc and replaced it but we still have the same problem is there anything else we can try.
We are a general galvanizer and use a low fume flux.
Galvanizing - Londonderry, Northern Ireland
2006
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A. As aluminium stays at the top of the kettle, by using your flux powder you can reduce your aluminium content to some extent, which you can throw on the kettle top and skim it off.
Regards,
- Riyadh, Saudi Arabia
A. I HAVE THIS PROBLEM SOME TIME AGO. ¿YOUR PROCESS IS CONTINUOUS OR BATCH? ¿IS WIRE OR STRIP?¿HOW MUCH ZINC HAVE THE BATH?
MAYBE YOU CAN PUT AN AIR LANCE INTO THE BATH(THE ALUMINIUM IS MORE REACTIVE AND WILL FORM OXIDE)
THERE IS ANOTHER "UNCONVENTIONAL" PROCESS THAT YOU CAN TRY: FOUND A BIG PIECE OF GREEN WOOD, AND PUT THIS UNDER THE ZINC. MAKE THIS WITH EXTREME CAUTION, THE GAS THAT COME FROM THE WOOD WILL OXIDIZE THE ALUMINIUM.I HOPE THIS CAN HELP YOU.
CALUR - CANELONES, URUGUAY
A. Dilution is really your only choice here I think. Have seen a similar situation, and seen all manner of "old wives tales" tried, including coconut husks, potatoes, oxygen lancing, top skimming, etc.
Pump out and dilute with fresh zinc. (If you can find any of this increasingly rare commodity)
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
Closely related topics:
Thread 54105, "Aluminium Addition to Galvanising Kettle"
Thread 25997, "Prevention and Removal of White Rust on Galvanizing"
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