Zinc consumption control in hot dip galvanizing

A. Hi Arvind. That sounds like the title to a good-sized textbook :-)

But this page offers very generous and detailed postings by Geoff Crowley & Dr. Thomas Cook. Please carefully describe your own situation or publicly follow up on one of their many specific points, or privately contract them for their services. Thanks!

Luck & Regards,

A. This is a big question, and would indeed take a book to answer. But you could make it much more specific with some more information.
What zinc consumption do you get now? What flux do you use? at what strength? Ratio? %Fe in flux? What pickle system? Rinsing tanks? (where and how many?)
What material being processed? Temp of zinc? and any more info you can think to share.

Your question is a little like "How can I make money?" There are a million answers.
So more specific background could yield helpful answers.

A. Atul,
Iron in flux does not cause dross in a "dry" kettle. Iron in flux does cause dross in a "wet" kettle. Is your kettle "dry" or "wet?" Usually a sudden increase in dross in a "dry" kettle means to me that the kettle is burning out. Usually due to dross packed against the vertical walls due to improper drossing. What method do you use for drossing?
In India (Tata Iron and Steel and Apollo in Madras), in South Africa (Barlow Rand), in USA, in South America, in Turkey, a tube is blown about every 6 seconds. For the outside of the pipes the blow ring can use heated air which does a better job AND retains heat on the pipes for the internal blow. For the inside blow we have found fluxes (published in METAL FINISHING) and other methods which increase the fluidity that greatly improve the internal draining before the blow. Very often there is four times or more zinc on the inside of the pipes as compared with the outside.
What do your inside zinc coating profiles look like? In South Africa the workers commented that when proper flux was used the zinc on the inside of the pipes was "As smooth as a baby's butt."
A steam accumulator near the blow head greatly improves internal blowing because the steam energy discharge is done in a much shorter time. Normally about 400 pipe volumes of steam are required to attain a proper internal blow. Exceptions are large bore which can be dealt with by other means.
Regards,

A. Sir:

I was in India twice. At one location the commercial flux had about 20% sodium chloride, thus a good result was NOT expected. We did overcome this bad flux by other means. The other location had very good flux by means of making up their own flux using relatively "clean" zinc chloride and "clean" ammonium chloride (impurities were less than 1% with moisture content of no consequence).

I have no idea where you got your technology: For example, is it European with high baumé low ACN flux or American with low baumé high ACN. Is your flux cold with a drying oven or hot and no drying oven.

Is your rinsing after acid pickling good, or is the iron +2 overpowering you flux solution.

With high zinc usage perhaps your kettle furnace is bad and you have a leak in your kettle.

Do you have a magnetic thickness gauge to determine the zinc thickness on your product?

What is your ash/production%? What is your dross/production%?

There are so many, many things that can and do "go wrong" that it is virtually impossible to "trouble shoot" from your question.

Regards,

A. You speak of a filter on your quench, but that seems unusual. When you say "filter", did you mean a flux treatment system?
If it's only a filter, what do you hope to get? There should not be undissolved solids in your flux.
There might be sludge on the floor of the tank, but hopefully not in suspension.

A. Hi Somen. We appended your inquiry to a thread on similar subjects, which may partially answer it for you. Perhaps with this new starting point it will be possible to fine tune your inquiry. Good luck.

Regards,

A. The kettle will hold more the older it gets. This is due to erosion of the inside and to becoming misshapen with time.

I kettle also has (normally) curved corners between sides and floor and between ends and floor, and between ends and sides. This reduces volume a little.

A nominal say 6 x 1.5 x 3m kettle holds 27m3 when full to the brim. But no-one runs a kettle that full, perhaps 100 mm down. So depth is 2.9 deep, so 26.1m3
If its say 10 years old, it might hold 28m3.

As you say, the density of molten zinc is lower than that of solid, so volume x density = tonnes in kettle.

Welcome cousin Irwan. We have dozens of threads about lead in galvanizing and nickel in galvanizing, and additional threads about zinc consumption, and it is my understanding based on reading them that neither of those metals is added for the purpose of reducing zinc consumption; and apparently neither is known to increase the amount of zinc consumption sufficiently to have merited a comment either.

But it's hard for me to 'read between the lines' because of my very limited knowledge of galvanizing. What is your hypothesis? Or what is your specific question so that a reader can educate both of us on this?

Regards,