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topic 54614

Can't get required 100 micron coating when galvanizing with Galfan zinc alloy

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March 20, 2010

we have added zinc alloy Galfan 5%al and zinc alloy Ni 0.05% in our continuous running plant.After addition we are not getting required coating i.e., 100 micron on steel.My question is how do we improve coating in presence of above.Or suggest what to do to get required coating thickness on article or reduction of above alloy from zinc bath.

Jamil Sheikh
- Lahore, Pakistan


March 22, 2010

Sir:

I presume you are using hot 5% to 10% hydrogen and balance nitrogen gas mixture to preheat the strip steel (and to act as a flux). I find your required 100 micron zinc coating quite thick. My new 26 gauge galv. roof for my grainery is coated by 25 microns of zinc (each side). A roofing "valley" of about 30 gauge has about 15 microns of zinc on it. I really wish I could buy steel sheet with 100 microns of zinc here.

I find your use of 0.05% nickel AND 5% aluminum very unusual. The 5% aluminum in Galfan FULLY inhibits any reactive alloy growth (zinc and iron reaction), so why would the expensive and cancer causing nickel be added? Also nickel is difficult to maintain in the bath.

Who recommended the use of nickel and why?

You already know that to increase strip zinc coating thickness, the usual is to raise the air knives and to reduce the volume of air through the knives.

On Thursday I have a scheduled phone call with a guy from ILZRO (International Lead and Zinc Research Organization) who was heavily involved in the original development of Galfan. I will ask him if Galfan can produce the coating thickness that you require and if nickel is recommended.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota 57747


March 25, 2010

Sir:

I spoke with the guy from ILZO today and he said that he did not know of any beneficial reason to use 0.05% nickel in galfan.

He also said that at very fast line speed with virtually no air knife blowing the MAXIMUM zinc coating would be around 50 microns. He also mentioned that with no air knife blowing there would be sag lines (which could be partially prevented using nitrogen gas blowing, which would be expensive).

If you want to speak directly to this guy then contact me privately through finishing.com and I will give you his phone number.

Regards,

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



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